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  97.     <ul>

  98. <li><a class="reference internal" href="#">What’s New in Python 2.7</a><ul>

  99. <li><a class="reference internal" href="#the-future-for-python-2-x">The Future for Python 2.x</a></li>

  100. <li><a class="reference internal" href="#changes-to-the-handling-of-deprecation-warnings">Changes to the Handling of Deprecation Warnings</a></li>

  101. <li><a class="reference internal" href="#python-3-1-features">Python 3.1 Features</a></li>

  102. <li><a class="reference internal" href="#pep-372-adding-an-ordered-dictionary-to-collections">PEP 372: Adding an Ordered Dictionary to collections</a></li>

  103. <li><a class="reference internal" href="#pep-378-format-specifier-for-thousands-separator">PEP 378: Format Specifier for Thousands Separator</a></li>

  104. <li><a class="reference internal" href="#pep-389-the-argparse-module-for-parsing-command-lines">PEP 389: The argparse Module for Parsing Command Lines</a></li>

  105. <li><a class="reference internal" href="#pep-391-dictionary-based-configuration-for-logging">PEP 391: Dictionary-Based Configuration For Logging</a></li>

  106. <li><a class="reference internal" href="#pep-3106-dictionary-views">PEP 3106: Dictionary Views</a></li>

  107. <li><a class="reference internal" href="#pep-3137-the-memoryview-object">PEP 3137: The memoryview Object</a></li>

  108. <li><a class="reference internal" href="#other-language-changes">Other Language Changes</a><ul>

  109. <li><a class="reference internal" href="#interpreter-changes">Interpreter Changes</a></li>

  110. <li><a class="reference internal" href="#optimizations">Optimizations</a></li>

  111. </ul>

  112. </li>

  113. <li><a class="reference internal" href="#new-and-improved-modules">New and Improved Modules</a><ul>

  114. <li><a class="reference internal" href="#new-module-importlib">New module: importlib</a></li>

  115. <li><a class="reference internal" href="#new-module-sysconfig">New module: sysconfig</a></li>

  116. <li><a class="reference internal" href="#ttk-themed-widgets-for-tk">ttk: Themed Widgets for Tk</a></li>

  117. <li><a class="reference internal" href="#updated-module-unittest">Updated module: unittest</a></li>

  118. <li><a class="reference internal" href="#updated-module-elementtree-1-3">Updated module: ElementTree 1.3</a></li>

  119. </ul>

  120. </li>

  121. <li><a class="reference internal" href="#build-and-c-api-changes">Build and C API Changes</a><ul>

  122. <li><a class="reference internal" href="#capsules">Capsules</a></li>

  123. <li><a class="reference internal" href="#port-specific-changes-windows">Port-Specific Changes: Windows</a></li>

  124. <li><a class="reference internal" href="#port-specific-changes-mac-os-x">Port-Specific Changes: Mac OS X</a></li>

  125. <li><a class="reference internal" href="#port-specific-changes-freebsd">Port-Specific Changes: FreeBSD</a></li>

  126. </ul>

  127. </li>

  128. <li><a class="reference internal" href="#other-changes-and-fixes">Other Changes and Fixes</a></li>

  129. <li><a class="reference internal" href="#porting-to-python-2-7">Porting to Python 2.7</a></li>

  130. <li><a class="reference internal" href="#new-features-added-to-python-2-7-maintenance-releases">New Features Added to Python 2.7 Maintenance Releases</a><ul>

  131. <li><a class="reference internal" href="#two-new-environment-variables-for-debug-mode">Two new environment variables for debug mode</a></li>

  132. <li><a class="reference internal" href="#pep-434-idle-enhancement-exception-for-all-branches">PEP 434: IDLE Enhancement Exception for All Branches</a></li>

  133. <li><a class="reference internal" href="#pep-466-network-security-enhancements-for-python-2-7">PEP 466: Network Security Enhancements for Python 2.7</a></li>

  134. <li><a class="reference internal" href="#pep-477-backport-ensurepip-pep-453-to-python-2-7">PEP 477: Backport ensurepip (PEP 453) to Python 2.7</a><ul>

  135. <li><a class="reference internal" href="#bootstrapping-pip-by-default">Bootstrapping pip By Default</a></li>

  136. <li><a class="reference internal" href="#documentation-changes">Documentation Changes</a></li>

  137. </ul>

  138. </li>

  139. <li><a class="reference internal" href="#pep-476-enabling-certificate-verification-by-default-for-stdlib-http-clients">PEP 476: Enabling certificate verification by default for stdlib http clients</a></li>

  140. <li><a class="reference internal" href="#pep-493-https-verification-migration-tools-for-python-2-7">PEP 493: HTTPS verification migration tools for Python 2.7</a></li>

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  143. </ul>

  144. </li>

  145. <li><a class="reference internal" href="#acknowledgements">Acknowledgements</a></li>

  146. </ul>

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  148. </ul>

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  237.   <section id="what-s-new-in-python-2-7">

  238. <h1>What’s New in Python 2.7<a class="headerlink" href="#what-s-new-in-python-2-7" title="Link to this heading">¶</a></h1>

  239. <dl class="field-list simple">

  240. <dt class="field-odd">Author<span class="colon">:</span></dt>

  241. <dd class="field-odd"><p>A.M. Kuchling (amk at amk.ca)</p>

  242. </dd>

  243. </dl>

  244. <p>This article explains the new features in Python 2.7.  Python 2.7 was released

  245. on July 3, 2010.</p>

  246. <p>Numeric handling has been improved in many ways, for both

  247. floating-point numbers and for the <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a> class.

  248. There are some useful additions to the standard library, such as a

  249. greatly enhanced <a class="reference internal" href="../library/unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate"><span class="pre">unittest</span></code></a> module, the <a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">argparse</span></code></a> module

  250. for parsing command-line options, convenient <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">OrderedDict</span></code></a>

  251. and <a class="reference internal" href="../library/collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Counter</span></code></a> classes in the <a class="reference internal" href="../library/collections.html#module-collections" title="collections: Container datatypes"><code class="xref py py-mod docutils literal notranslate"><span class="pre">collections</span></code></a> module,

  252. and many other improvements.</p>

  253. <p>Python 2.7 is planned to be the last of the 2.x releases, so we worked

  254. on making it a good release for the long term.  To help with porting

  255. to Python 3, several new features from the Python 3.x series have been

  256. included in 2.7.</p>

  257. <p>This article doesn’t attempt to provide a complete specification of

  258. the new features, but instead provides a convenient overview.  For

  259. full details, you should refer to the documentation for Python 2.7 at

  260. <a class="reference external" href="https://docs.python.org">https://docs.python.org</a>. If you want to understand the rationale for

  261. the design and implementation, refer to the PEP for a particular new

  262. feature or the issue on <a class="reference external" href="https://bugs.python.org">https://bugs.python.org</a> in which a change was

  263. discussed.  Whenever possible, “What’s New in Python” links to the

  264. bug/patch item for each change.</p>

  265. <section id="the-future-for-python-2-x">

  266. <span id="whatsnew27-python31"></span><h2>The Future for Python 2.x<a class="headerlink" href="#the-future-for-python-2-x" title="Link to this heading">¶</a></h2>

  267. <p>Python 2.7 is the last major release in the 2.x series, as the Python

  268. maintainers have shifted the focus of their new feature development efforts

  269. to the Python 3.x series. This means that while Python 2 continues to

  270. receive bug fixes, and to be updated to build correctly on new hardware and

  271. versions of supported operated systems, there will be no new full feature

  272. releases for the language or standard library.</p>

  273. <p>However, while there is a large common subset between Python 2.7 and Python

  274. 3, and many of the changes involved in migrating to that common subset, or

  275. directly to Python 3, can be safely automated, some other changes (notably

  276. those associated with Unicode handling) may require careful consideration,

  277. and preferably robust automated regression test suites, to migrate

  278. effectively.</p>

  279. <p>This means that Python 2.7 will remain in place for a long time, providing a

  280. stable and supported base platform for production systems that have not yet

  281. been ported to Python 3. The full expected lifecycle of the Python 2.7

  282. series is detailed in <span class="target" id="index-0"></span><a class="pep reference external" href="https://peps.python.org/pep-0373/"><strong>PEP 373</strong></a>.</p>

  283. <p>Some key consequences of the long-term significance of 2.7 are:</p>

  284. <ul class="simple">

  285. <li><p>As noted above, the 2.7 release has a much longer period of maintenance

  286. when compared to earlier 2.x versions. Python 2.7 is currently expected to

  287. remain supported by the core development team (receiving security updates

  288. and other bug fixes) until at least 2020 (10 years after its initial

  289. release, compared to the more typical support period of 18–24 months).</p></li>

  290. <li><p>As the Python 2.7 standard library ages, making effective use of the

  291. Python Package Index (either directly or via a redistributor) becomes

  292. more important for Python 2 users. In addition to a wide variety of third

  293. party packages for various tasks, the available packages include backports

  294. of new modules and features from the Python 3 standard library that are

  295. compatible with Python 2, as well as various tools and libraries that can

  296. make it easier to migrate to Python 3. The <a class="reference external" href="https://packaging.python.org">Python Packaging User Guide</a> provides guidance on downloading and

  297. installing software from the Python Package Index.</p></li>

  298. <li><p>While the preferred approach to enhancing Python 2 is now the publication

  299. of new packages on the Python Package Index, this approach doesn’t

  300. necessarily work in all cases, especially those related to network

  301. security. In exceptional cases that cannot be handled adequately by

  302. publishing new or updated packages on PyPI, the Python Enhancement

  303. Proposal process may be used to make the case for adding new features

  304. directly to the Python 2 standard library. Any such additions, and the

  305. maintenance releases where they were added, will be noted in the

  306. <a class="reference internal" href="#py27-maintenance-enhancements"><span class="std std-ref">New Features Added to Python 2.7 Maintenance Releases</span></a> section below.</p></li>

  307. </ul>

  308. <p>For projects wishing to migrate from Python 2 to Python 3, or for library

  309. and framework developers wishing to support users on both Python 2 and

  310. Python 3, there are a variety of tools and guides available to help decide

  311. on a suitable approach and manage some of the technical details involved.

  312. The recommended starting point is the <a class="reference internal" href="../howto/pyporting.html#pyporting-howto"><span class="std std-ref">How to port Python 2 Code to Python 3</span></a> HOWTO guide.</p>

  313. </section>

  314. <section id="changes-to-the-handling-of-deprecation-warnings">

  315. <h2>Changes to the Handling of Deprecation Warnings<a class="headerlink" href="#changes-to-the-handling-of-deprecation-warnings" title="Link to this heading">¶</a></h2>

  316. <p>For Python 2.7, a policy decision was made to silence warnings only of

  317. interest to developers by default.  <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">DeprecationWarning</span></code></a> and its

  318. descendants are now ignored unless otherwise requested, preventing

  319. users from seeing warnings triggered by an application.  This change

  320. was also made in the branch that became Python 3.2. (Discussed

  321. on stdlib-sig and carried out in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7319">bpo-7319</a>.)</p>

  322. <p>In previous releases, <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">DeprecationWarning</span></code></a> messages were

  323. enabled by default, providing Python developers with a clear

  324. indication of where their code may break in a future major version

  325. of Python.</p>

  326. <p>However, there are increasingly many users of Python-based

  327. applications who are not directly involved in the development of

  328. those applications.  <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">DeprecationWarning</span></code></a> messages are

  329. irrelevant to such users, making them worry about an application

  330. that’s actually working correctly and burdening application developers

  331. with responding to these concerns.</p>

  332. <p>You can re-enable display of <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">DeprecationWarning</span></code></a> messages by

  333. running Python with the <a class="reference internal" href="../using/cmdline.html#cmdoption-W"><code class="xref std std-option docutils literal notranslate"><span class="pre">-Wdefault</span></code></a> (short form:

  334. <a class="reference internal" href="../using/cmdline.html#cmdoption-W"><code class="xref std std-option docutils literal notranslate"><span class="pre">-Wd</span></code></a>) switch, or by setting the <span class="target" id="index-1"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONWARNINGS"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONWARNINGS</span></code></a>

  335. environment variable to <code class="docutils literal notranslate"><span class="pre">&quot;default&quot;</span></code> (or <code class="docutils literal notranslate"><span class="pre">&quot;d&quot;</span></code>) before running

  336. Python.  Python code can also re-enable them

  337. by calling <code class="docutils literal notranslate"><span class="pre">warnings.simplefilter('default')</span></code>.</p>

  338. <p>The <code class="docutils literal notranslate"><span class="pre">unittest</span></code> module also automatically reenables deprecation warnings

  339. when running tests.</p>

  340. </section>

  341. <section id="python-3-1-features">

  342. <h2>Python 3.1 Features<a class="headerlink" href="#python-3-1-features" title="Link to this heading">¶</a></h2>

  343. <p>Much as Python 2.6 incorporated features from Python 3.0,

  344. version 2.7 incorporates some of the new features

  345. in Python 3.1.  The 2.x series continues to provide tools

  346. for migrating to the 3.x series.</p>

  347. <p>A partial list of 3.1 features that were backported to 2.7:</p>

  348. <ul class="simple">

  349. <li><p>The syntax for set literals (<code class="docutils literal notranslate"><span class="pre">{1,2,3}</span></code> is a mutable set).</p></li>

  350. <li><p>Dictionary and set comprehensions (<code class="docutils literal notranslate"><span class="pre">{i:</span> <span class="pre">i*2</span> <span class="pre">for</span> <span class="pre">i</span> <span class="pre">in</span> <span class="pre">range(3)}</span></code>).</p></li>

  351. <li><p>Multiple context managers in a single <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement.</p></li>

  352. <li><p>A new version of the <a class="reference internal" href="../library/io.html#module-io" title="io: Core tools for working with streams."><code class="xref py py-mod docutils literal notranslate"><span class="pre">io</span></code></a> library, rewritten in C for performance.</p></li>

  353. <li><p>The ordered-dictionary type described in <a class="reference internal" href="#pep-0372"><span class="std std-ref">PEP 372: Adding an Ordered Dictionary to collections</span></a>.</p></li>

  354. <li><p>The new <code class="docutils literal notranslate"><span class="pre">&quot;,&quot;</span></code> format specifier described in <a class="reference internal" href="#pep-0378"><span class="std std-ref">PEP 378: Format Specifier for Thousands Separator</span></a>.</p></li>

  355. <li><p>The <a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> object.</p></li>

  356. <li><p>A small subset of the <a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib</span></code></a> module,

  357. <a class="reference external" href="#importlib-section">described below</a>.</p></li>

  358. <li><p>The <a class="reference internal" href="../library/functions.html#repr" title="repr"><code class="xref py py-func docutils literal notranslate"><span class="pre">repr()</span></code></a> of a float <code class="docutils literal notranslate"><span class="pre">x</span></code> is shorter in many cases: it’s now

  359. based on the shortest decimal string that’s guaranteed to round back

  360. to <code class="docutils literal notranslate"><span class="pre">x</span></code>.  As in previous versions of Python, it’s guaranteed that

  361. <code class="docutils literal notranslate"><span class="pre">float(repr(x))</span></code> recovers <code class="docutils literal notranslate"><span class="pre">x</span></code>.</p></li>

  362. <li><p>Float-to-string and string-to-float conversions are correctly rounded.

  363. The <a class="reference internal" href="../library/functions.html#round" title="round"><code class="xref py py-func docutils literal notranslate"><span class="pre">round()</span></code></a> function is also now correctly rounded.</p></li>

  364. <li><p>The <a class="reference internal" href="../c-api/capsule.html#c.PyCapsule" title="PyCapsule"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyCapsule</span></code></a> type, used to provide a C API for extension modules.</p></li>

  365. <li><p>The <a class="reference internal" href="../c-api/long.html#c.PyLong_AsLongAndOverflow" title="PyLong_AsLongAndOverflow"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyLong_AsLongAndOverflow()</span></code></a> C API function.</p></li>

  366. </ul>

  367. <p>Other new Python3-mode warnings include:</p>

  368. <ul class="simple">

  369. <li><p><code class="xref py py-func docutils literal notranslate"><span class="pre">operator.isCallable()</span></code> and <code class="xref py py-func docutils literal notranslate"><span class="pre">operator.sequenceIncludes()</span></code>,

  370. which are not supported in 3.x, now trigger warnings.</p></li>

  371. <li><p>The <code class="xref std std-option docutils literal notranslate"><span class="pre">-3</span></code> switch now automatically

  372. enables the <code class="xref std std-option docutils literal notranslate"><span class="pre">-Qwarn</span></code> switch that causes warnings

  373. about using classic division with integers and long integers.</p></li>

  374. </ul>

  375. </section>

  376. <section id="pep-372-adding-an-ordered-dictionary-to-collections">

  377. <span id="pep-0372"></span><h2>PEP 372: Adding an Ordered Dictionary to collections<a class="headerlink" href="#pep-372-adding-an-ordered-dictionary-to-collections" title="Link to this heading">¶</a></h2>

  378. <p>Regular Python dictionaries iterate over key/value pairs in arbitrary order.

  379. Over the years, a number of authors have written alternative implementations

  380. that remember the order that the keys were originally inserted.  Based on

  381. the experiences from those implementations, 2.7 introduces a new

  382. <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">OrderedDict</span></code></a> class in the <a class="reference internal" href="../library/collections.html#module-collections" title="collections: Container datatypes"><code class="xref py py-mod docutils literal notranslate"><span class="pre">collections</span></code></a> module.</p>

  383. <p>The <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">OrderedDict</span></code></a> API provides the same interface as regular

  384. dictionaries but iterates over keys and values in a guaranteed order

  385. depending on when a key was first inserted:</p>

  386. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">collections</span> <span class="kn">import</span> <span class="n">OrderedDict</span>

  387. <span class="gp">&gt;&gt;&gt; </span><span class="n">d</span> <span class="o">=</span> <span class="n">OrderedDict</span><span class="p">([(</span><span class="s1">&#39;first&#39;</span><span class="p">,</span> <span class="mi">1</span><span class="p">),</span>

  388. <span class="gp">... </span>                 <span class="p">(</span><span class="s1">&#39;second&#39;</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span>

  389. <span class="gp">... </span>                 <span class="p">(</span><span class="s1">&#39;third&#39;</span><span class="p">,</span> <span class="mi">3</span><span class="p">)])</span>

  390. <span class="gp">&gt;&gt;&gt; </span><span class="n">d</span><span class="o">.</span><span class="n">items</span><span class="p">()</span>

  391. <span class="go">[(&#39;first&#39;, 1), (&#39;second&#39;, 2), (&#39;third&#39;, 3)]</span>

  392. </pre></div>

  393. </div>

  394. <p>If a new entry overwrites an existing entry, the original insertion

  395. position is left unchanged:</p>

  396. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">d</span><span class="p">[</span><span class="s1">&#39;second&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="mi">4</span>

  397. <span class="gp">&gt;&gt;&gt; </span><span class="n">d</span><span class="o">.</span><span class="n">items</span><span class="p">()</span>

  398. <span class="go">[(&#39;first&#39;, 1), (&#39;second&#39;, 4), (&#39;third&#39;, 3)]</span>

  399. </pre></div>

  400. </div>

  401. <p>Deleting an entry and reinserting it will move it to the end:</p>

  402. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">del</span> <span class="n">d</span><span class="p">[</span><span class="s1">&#39;second&#39;</span><span class="p">]</span>

  403. <span class="gp">&gt;&gt;&gt; </span><span class="n">d</span><span class="p">[</span><span class="s1">&#39;second&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="mi">5</span>

  404. <span class="gp">&gt;&gt;&gt; </span><span class="n">d</span><span class="o">.</span><span class="n">items</span><span class="p">()</span>

  405. <span class="go">[(&#39;first&#39;, 1), (&#39;third&#39;, 3), (&#39;second&#39;, 5)]</span>

  406. </pre></div>

  407. </div>

  408. <p>The <a class="reference internal" href="../library/collections.html#collections.OrderedDict.popitem" title="collections.OrderedDict.popitem"><code class="xref py py-meth docutils literal notranslate"><span class="pre">popitem()</span></code></a> method has an optional <em>last</em>

  409. argument that defaults to <code class="docutils literal notranslate"><span class="pre">True</span></code>.  If <em>last</em> is true, the most recently

  410. added key is returned and removed; if it’s false, the

  411. oldest key is selected:</p>

  412. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">od</span> <span class="o">=</span> <span class="n">OrderedDict</span><span class="p">([(</span><span class="n">x</span><span class="p">,</span><span class="mi">0</span><span class="p">)</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">20</span><span class="p">)])</span>

  413. <span class="gp">&gt;&gt;&gt; </span><span class="n">od</span><span class="o">.</span><span class="n">popitem</span><span class="p">()</span>

  414. <span class="go">(19, 0)</span>

  415. <span class="gp">&gt;&gt;&gt; </span><span class="n">od</span><span class="o">.</span><span class="n">popitem</span><span class="p">()</span>

  416. <span class="go">(18, 0)</span>

  417. <span class="gp">&gt;&gt;&gt; </span><span class="n">od</span><span class="o">.</span><span class="n">popitem</span><span class="p">(</span><span class="n">last</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>

  418. <span class="go">(0, 0)</span>

  419. <span class="gp">&gt;&gt;&gt; </span><span class="n">od</span><span class="o">.</span><span class="n">popitem</span><span class="p">(</span><span class="n">last</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>

  420. <span class="go">(1, 0)</span>

  421. </pre></div>

  422. </div>

  423. <p>Comparing two ordered dictionaries checks both the keys and values,

  424. and requires that the insertion order was the same:</p>

  425. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">od1</span> <span class="o">=</span> <span class="n">OrderedDict</span><span class="p">([(</span><span class="s1">&#39;first&#39;</span><span class="p">,</span> <span class="mi">1</span><span class="p">),</span>

  426. <span class="gp">... </span>                   <span class="p">(</span><span class="s1">&#39;second&#39;</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span>

  427. <span class="gp">... </span>                   <span class="p">(</span><span class="s1">&#39;third&#39;</span><span class="p">,</span> <span class="mi">3</span><span class="p">)])</span>

  428. <span class="gp">&gt;&gt;&gt; </span><span class="n">od2</span> <span class="o">=</span> <span class="n">OrderedDict</span><span class="p">([(</span><span class="s1">&#39;third&#39;</span><span class="p">,</span> <span class="mi">3</span><span class="p">),</span>

  429. <span class="gp">... </span>                   <span class="p">(</span><span class="s1">&#39;first&#39;</span><span class="p">,</span> <span class="mi">1</span><span class="p">),</span>

  430. <span class="gp">... </span>                   <span class="p">(</span><span class="s1">&#39;second&#39;</span><span class="p">,</span> <span class="mi">2</span><span class="p">)])</span>

  431. <span class="gp">&gt;&gt;&gt; </span><span class="n">od1</span> <span class="o">==</span> <span class="n">od2</span>

  432. <span class="go">False</span>

  433. <span class="gp">&gt;&gt;&gt; </span><span class="c1"># Move &#39;third&#39; key to the end</span>

  434. <span class="gp">&gt;&gt;&gt; </span><span class="k">del</span> <span class="n">od2</span><span class="p">[</span><span class="s1">&#39;third&#39;</span><span class="p">];</span> <span class="n">od2</span><span class="p">[</span><span class="s1">&#39;third&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="mi">3</span>

  435. <span class="gp">&gt;&gt;&gt; </span><span class="n">od1</span> <span class="o">==</span> <span class="n">od2</span>

  436. <span class="go">True</span>

  437. </pre></div>

  438. </div>

  439. <p>Comparing an <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">OrderedDict</span></code></a> with a regular dictionary

  440. ignores the insertion order and just compares the keys and values.</p>

  441. <p>How does the <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">OrderedDict</span></code></a> work?  It maintains a

  442. doubly linked list of keys, appending new keys to the list as they’re inserted.

  443. A secondary dictionary maps keys to their corresponding list node, so

  444. deletion doesn’t have to traverse the entire linked list and therefore

  445. remains <em>O</em>(1).</p>

  446. <p>The standard library now supports use of ordered dictionaries in several

  447. modules.</p>

  448. <ul class="simple">

  449. <li><p>The <a class="reference internal" href="../library/configparser.html#module-configparser" title="configparser: Configuration file parser."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ConfigParser</span></code></a> module uses them by default, meaning that

  450. configuration files can now be read, modified, and then written back

  451. in their original order.</p></li>

  452. <li><p>The <a class="reference internal" href="../library/collections.html#collections.somenamedtuple._asdict" title="collections.somenamedtuple._asdict"><code class="xref py py-meth docutils literal notranslate"><span class="pre">_asdict()</span></code></a> method for

  453. <a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate"><span class="pre">collections.namedtuple()</span></code></a> now returns an ordered dictionary with the

  454. values appearing in the same order as the underlying tuple indices.</p></li>

  455. <li><p>The <a class="reference internal" href="../library/json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json</span></code></a> module’s <a class="reference internal" href="../library/json.html#json.JSONDecoder" title="json.JSONDecoder"><code class="xref py py-class docutils literal notranslate"><span class="pre">JSONDecoder</span></code></a> class

  456. constructor was extended with an <em>object_pairs_hook</em> parameter to

  457. allow <code class="xref py py-class docutils literal notranslate"><span class="pre">OrderedDict</span></code> instances to be built by the decoder.

  458. Support was also added for third-party tools like

  459. <a class="reference external" href="https://pyyaml.org/">PyYAML</a>.</p></li>

  460. </ul>

  461. <div class="admonition seealso">

  462. <p class="admonition-title">See also</p>

  463. <dl class="simple">

  464. <dt><span class="target" id="index-2"></span><a class="pep reference external" href="https://peps.python.org/pep-0372/"><strong>PEP 372</strong></a> - Adding an ordered dictionary to collections</dt><dd><p>PEP written by Armin Ronacher and Raymond Hettinger;

  465. implemented by Raymond Hettinger.</p>

  466. </dd>

  467. </dl>

  468. </div>

  469. </section>

  470. <section id="pep-378-format-specifier-for-thousands-separator">

  471. <span id="pep-0378"></span><h2>PEP 378: Format Specifier for Thousands Separator<a class="headerlink" href="#pep-378-format-specifier-for-thousands-separator" title="Link to this heading">¶</a></h2>

  472. <p>To make program output more readable, it can be useful to add

  473. separators to large numbers, rendering them as

  474. 18,446,744,073,709,551,616 instead of 18446744073709551616.</p>

  475. <p>The fully general solution for doing this is the <a class="reference internal" href="../library/locale.html#module-locale" title="locale: Internationalization services."><code class="xref py py-mod docutils literal notranslate"><span class="pre">locale</span></code></a> module,

  476. which can use different separators (“,” in North America, “.” in

  477. Europe) and different grouping sizes, but <a class="reference internal" href="../library/locale.html#module-locale" title="locale: Internationalization services."><code class="xref py py-mod docutils literal notranslate"><span class="pre">locale</span></code></a> is complicated

  478. to use and unsuitable for multi-threaded applications where different

  479. threads are producing output for different locales.</p>

  480. <p>Therefore, a simple comma-grouping mechanism has been added to the

  481. mini-language used by the <a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.format()</span></code></a> method.  When

  482. formatting a floating-point number, simply include a comma between the

  483. width and the precision:</p>

  484. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="s1">&#39;</span><span class="si">{:20,.2f}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mf">18446744073709551616.0</span><span class="p">)</span>

  485. <span class="go">&#39;18,446,744,073,709,551,616.00&#39;</span>

  486. </pre></div>

  487. </div>

  488. <p>When formatting an integer, include the comma after the width:</p>

  489. <div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="s1">&#39;</span><span class="si">{:20,d}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mi">18446744073709551616</span><span class="p">)</span>

  490. <span class="go">&#39;18,446,744,073,709,551,616&#39;</span>

  491. </pre></div>

  492. </div>

  493. <p>This mechanism is not adaptable at all; commas are always used as the

  494. separator and the grouping is always into three-digit groups.  The

  495. comma-formatting mechanism isn’t as general as the <a class="reference internal" href="../library/locale.html#module-locale" title="locale: Internationalization services."><code class="xref py py-mod docutils literal notranslate"><span class="pre">locale</span></code></a>

  496. module, but it’s easier to use.</p>

  497. <div class="admonition seealso">

  498. <p class="admonition-title">See also</p>

  499. <dl class="simple">

  500. <dt><span class="target" id="index-3"></span><a class="pep reference external" href="https://peps.python.org/pep-0378/"><strong>PEP 378</strong></a> - Format Specifier for Thousands Separator</dt><dd><p>PEP written by Raymond Hettinger; implemented by Eric Smith.</p>

  501. </dd>

  502. </dl>

  503. </div>

  504. </section>

  505. <section id="pep-389-the-argparse-module-for-parsing-command-lines">

  506. <h2>PEP 389: The argparse Module for Parsing Command Lines<a class="headerlink" href="#pep-389-the-argparse-module-for-parsing-command-lines" title="Link to this heading">¶</a></h2>

  507. <p>The <a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">argparse</span></code></a> module for parsing command-line arguments was

  508. added as a more powerful replacement for the

  509. <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> module.</p>

  510. <p>This means Python now supports three different modules for parsing

  511. command-line arguments: <a class="reference internal" href="../library/getopt.html#module-getopt" title="getopt: Portable parser for command line options; support both short and long option names."><code class="xref py py-mod docutils literal notranslate"><span class="pre">getopt</span></code></a>, <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>, and

  512. <a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">argparse</span></code></a>.  The <a class="reference internal" href="../library/getopt.html#module-getopt" title="getopt: Portable parser for command line options; support both short and long option names."><code class="xref py py-mod docutils literal notranslate"><span class="pre">getopt</span></code></a> module closely resembles the C

  513. library’s <code class="xref c c-func docutils literal notranslate"><span class="pre">getopt()</span></code> function, so it remains useful if you’re writing a

  514. Python prototype that will eventually be rewritten in C.

  515. <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> becomes redundant, but there are no plans to remove it

  516. because there are many scripts still using it, and there’s no

  517. automated way to update these scripts.  (Making the <a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">argparse</span></code></a>

  518. API consistent with <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>’s interface was discussed but

  519. rejected as too messy and difficult.)</p>

  520. <p>In short, if you’re writing a new script and don’t need to worry

  521. about compatibility with earlier versions of Python, use

  522. <a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">argparse</span></code></a> instead of <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>.</p>

  523. <p>Here’s an example:</p>

  524. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">argparse</span>

  525. 

  526. <span class="n">parser</span> <span class="o">=</span> <span class="n">argparse</span><span class="o">.</span><span class="n">ArgumentParser</span><span class="p">(</span><span class="n">description</span><span class="o">=</span><span class="s1">&#39;Command-line example.&#39;</span><span class="p">)</span>

  527. 

  528. <span class="c1"># Add optional switches</span>

  529. <span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">&#39;-v&#39;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s1">&#39;store_true&#39;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">&#39;is_verbose&#39;</span><span class="p">,</span>

  530.                     <span class="n">help</span><span class="o">=</span><span class="s1">&#39;produce verbose output&#39;</span><span class="p">)</span>

  531. <span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">&#39;-o&#39;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s1">&#39;store&#39;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">&#39;output&#39;</span><span class="p">,</span>

  532.                     <span class="n">metavar</span><span class="o">=</span><span class="s1">&#39;FILE&#39;</span><span class="p">,</span>

  533.                     <span class="n">help</span><span class="o">=</span><span class="s1">&#39;direct output to FILE instead of stdout&#39;</span><span class="p">)</span>

  534. <span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="s1">&#39;-C&#39;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s1">&#39;store&#39;</span><span class="p">,</span> <span class="nb">type</span><span class="o">=</span><span class="nb">int</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">&#39;context&#39;</span><span class="p">,</span>

  535.                     <span class="n">metavar</span><span class="o">=</span><span class="s1">&#39;NUM&#39;</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span>

  536.                     <span class="n">help</span><span class="o">=</span><span class="s1">&#39;display NUM lines of added context&#39;</span><span class="p">)</span>

  537. 

  538. <span class="c1"># Allow any number of additional arguments.</span>

  539. <span class="n">parser</span><span class="o">.</span><span class="n">add_argument</span><span class="p">(</span><span class="n">nargs</span><span class="o">=</span><span class="s1">&#39;*&#39;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s1">&#39;store&#39;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">&#39;inputs&#39;</span><span class="p">,</span>

  540.                     <span class="n">help</span><span class="o">=</span><span class="s1">&#39;input filenames (default is stdin)&#39;</span><span class="p">)</span>

  541. 

  542. <span class="n">args</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">()</span>

  543. <span class="nb">print</span> <span class="n">args</span><span class="o">.</span><span class="vm">__dict__</span>

  544. </pre></div>

  545. </div>

  546. <p>Unless you override it, <code class="xref std std-option docutils literal notranslate"><span class="pre">-h</span></code> and <code class="xref std std-option docutils literal notranslate"><span class="pre">--help</span></code> switches

  547. are automatically added, and produce neatly formatted output:</p>

  548. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">-&gt;</span> <span class="o">./</span><span class="n">python</span><span class="o">.</span><span class="n">exe</span> <span class="n">argparse</span><span class="o">-</span><span class="n">example</span><span class="o">.</span><span class="n">py</span> <span class="o">--</span><span class="n">help</span>

  549. <span class="n">usage</span><span class="p">:</span> <span class="n">argparse</span><span class="o">-</span><span class="n">example</span><span class="o">.</span><span class="n">py</span> <span class="p">[</span><span class="o">-</span><span class="n">h</span><span class="p">]</span> <span class="p">[</span><span class="o">-</span><span class="n">v</span><span class="p">]</span> <span class="p">[</span><span class="o">-</span><span class="n">o</span> <span class="n">FILE</span><span class="p">]</span> <span class="p">[</span><span class="o">-</span><span class="n">C</span> <span class="n">NUM</span><span class="p">]</span> <span class="p">[</span><span class="n">inputs</span> <span class="p">[</span><span class="n">inputs</span> <span class="o">...</span><span class="p">]]</span>

  550. 

  551. <span class="n">Command</span><span class="o">-</span><span class="n">line</span> <span class="n">example</span><span class="o">.</span>

  552. 

  553. <span class="n">positional</span> <span class="n">arguments</span><span class="p">:</span>

  554.   <span class="n">inputs</span>      <span class="nb">input</span> <span class="n">filenames</span> <span class="p">(</span><span class="n">default</span> <span class="ow">is</span> <span class="n">stdin</span><span class="p">)</span>

  555. 

  556. <span class="n">optional</span> <span class="n">arguments</span><span class="p">:</span>

  557.   <span class="o">-</span><span class="n">h</span><span class="p">,</span> <span class="o">--</span><span class="n">help</span>  <span class="n">show</span> <span class="n">this</span> <span class="n">help</span> <span class="n">message</span> <span class="ow">and</span> <span class="n">exit</span>

  558.   <span class="o">-</span><span class="n">v</span>          <span class="n">produce</span> <span class="n">verbose</span> <span class="n">output</span>

  559.   <span class="o">-</span><span class="n">o</span> <span class="n">FILE</span>     <span class="n">direct</span> <span class="n">output</span> <span class="n">to</span> <span class="n">FILE</span> <span class="n">instead</span> <span class="n">of</span> <span class="n">stdout</span>

  560.   <span class="o">-</span><span class="n">C</span> <span class="n">NUM</span>      <span class="n">display</span> <span class="n">NUM</span> <span class="n">lines</span> <span class="n">of</span> <span class="n">added</span> <span class="n">context</span>

  561. </pre></div>

  562. </div>

  563. <p>As with <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>, the command-line switches and arguments

  564. are returned as an object with attributes named by the <em>dest</em> parameters:</p>

  565. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">-&gt;</span> <span class="o">./</span><span class="n">python</span><span class="o">.</span><span class="n">exe</span> <span class="n">argparse</span><span class="o">-</span><span class="n">example</span><span class="o">.</span><span class="n">py</span> <span class="o">-</span><span class="n">v</span>

  566. <span class="p">{</span><span class="s1">&#39;output&#39;</span><span class="p">:</span> <span class="kc">None</span><span class="p">,</span>

  567.  <span class="s1">&#39;is_verbose&#39;</span><span class="p">:</span> <span class="kc">True</span><span class="p">,</span>

  568.  <span class="s1">&#39;context&#39;</span><span class="p">:</span> <span class="mi">0</span><span class="p">,</span>

  569.  <span class="s1">&#39;inputs&#39;</span><span class="p">:</span> <span class="p">[]}</span>

  570. 

  571. <span class="o">-&gt;</span> <span class="o">./</span><span class="n">python</span><span class="o">.</span><span class="n">exe</span> <span class="n">argparse</span><span class="o">-</span><span class="n">example</span><span class="o">.</span><span class="n">py</span> <span class="o">-</span><span class="n">v</span> <span class="o">-</span><span class="n">o</span> <span class="o">/</span><span class="n">tmp</span><span class="o">/</span><span class="n">output</span> <span class="o">-</span><span class="n">C</span> <span class="mi">4</span> <span class="n">file1</span> <span class="n">file2</span>

  572. <span class="p">{</span><span class="s1">&#39;output&#39;</span><span class="p">:</span> <span class="s1">&#39;/tmp/output&#39;</span><span class="p">,</span>

  573.  <span class="s1">&#39;is_verbose&#39;</span><span class="p">:</span> <span class="kc">True</span><span class="p">,</span>

  574.  <span class="s1">&#39;context&#39;</span><span class="p">:</span> <span class="mi">4</span><span class="p">,</span>

  575.  <span class="s1">&#39;inputs&#39;</span><span class="p">:</span> <span class="p">[</span><span class="s1">&#39;file1&#39;</span><span class="p">,</span> <span class="s1">&#39;file2&#39;</span><span class="p">]}</span>

  576. </pre></div>

  577. </div>

  578. <p><a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">argparse</span></code></a> has much fancier validation than <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>; you

  579. can specify an exact number of arguments as an integer, 0 or more

  580. arguments by passing <code class="docutils literal notranslate"><span class="pre">'*'</span></code>, 1 or more by passing <code class="docutils literal notranslate"><span class="pre">'+'</span></code>, or an

  581. optional argument with <code class="docutils literal notranslate"><span class="pre">'?'</span></code>.  A top-level parser can contain

  582. sub-parsers to define subcommands that have different sets of

  583. switches, as in <code class="docutils literal notranslate"><span class="pre">svn</span> <span class="pre">commit</span></code>, <code class="docutils literal notranslate"><span class="pre">svn</span> <span class="pre">checkout</span></code>, etc.  You can

  584. specify an argument’s type as <a class="reference internal" href="../library/argparse.html#argparse.FileType" title="argparse.FileType"><code class="xref py py-class docutils literal notranslate"><span class="pre">FileType</span></code></a>, which will

  585. automatically open files for you and understands that <code class="docutils literal notranslate"><span class="pre">'-'</span></code> means

  586. standard input or output.</p>

  587. <div class="admonition seealso">

  588. <p class="admonition-title">See also</p>

  589. <dl class="simple">

  590. <dt><a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">argparse</span></code></a> documentation</dt><dd><p>The documentation page of the argparse module.</p>

  591. </dd>

  592. <dt><a class="reference internal" href="../library/argparse.html#upgrading-optparse-code"><span class="std std-ref">Upgrading optparse code</span></a></dt><dd><p>Part of the Python documentation, describing how to convert

  593. code that uses <a class="reference internal" href="../library/optparse.html#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>.</p>

  594. </dd>

  595. <dt><span class="target" id="index-4"></span><a class="pep reference external" href="https://peps.python.org/pep-0389/"><strong>PEP 389</strong></a> - argparse - New Command Line Parsing Module</dt><dd><p>PEP written and implemented by Steven Bethard.</p>

  596. </dd>

  597. </dl>

  598. </div>

  599. </section>

  600. <section id="pep-391-dictionary-based-configuration-for-logging">

  601. <h2>PEP 391: Dictionary-Based Configuration For Logging<a class="headerlink" href="#pep-391-dictionary-based-configuration-for-logging" title="Link to this heading">¶</a></h2>

  602. <p>The <a class="reference internal" href="../library/logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code></a> module is very flexible; applications can define

  603. a tree of logging subsystems, and each logger in this tree can filter

  604. out certain messages, format them differently, and direct messages to

  605. a varying number of handlers.</p>

  606. <p>All this flexibility can require a lot of configuration.  You can

  607. write Python statements to create objects and set their properties,

  608. but a complex set-up requires verbose but boring code.

  609. <a class="reference internal" href="../library/logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code></a> also supports a <a class="reference internal" href="../library/logging.config.html#logging.config.fileConfig" title="logging.config.fileConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">fileConfig()</span></code></a>

  610. function that parses a file, but the file format doesn’t support

  611. configuring filters, and it’s messier to generate programmatically.</p>

  612. <p>Python 2.7 adds a <a class="reference internal" href="../library/logging.config.html#logging.config.dictConfig" title="logging.config.dictConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">dictConfig()</span></code></a> function that

  613. uses a dictionary to configure logging.  There are many ways to

  614. produce a dictionary from different sources: construct one with code;

  615. parse a file containing JSON; or use a YAML parsing library if one is

  616. installed.  For more information see <a class="reference internal" href="../library/logging.config.html#logging-config-api"><span class="std std-ref">Configuration functions</span></a>.</p>

  617. <p>The following example configures two loggers, the root logger and a

  618. logger named “network”.  Messages sent to the root logger will be

  619. sent to the system log using the syslog protocol, and messages

  620. to the “network” logger will be written to a <code class="file docutils literal notranslate"><span class="pre">network.log</span></code> file

  621. that will be rotated once the log reaches 1MB.</p>

  622. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">logging</span>

  623. <span class="kn">import</span> <span class="nn">logging.config</span>

  624. 

  625. <span class="n">configdict</span> <span class="o">=</span> <span class="p">{</span>

  626.  <span class="s1">&#39;version&#39;</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span>    <span class="c1"># Configuration schema in use; must be 1 for now</span>

  627.  <span class="s1">&#39;formatters&#39;</span><span class="p">:</span> <span class="p">{</span>

  628.      <span class="s1">&#39;standard&#39;</span><span class="p">:</span> <span class="p">{</span>

  629.          <span class="s1">&#39;format&#39;</span><span class="p">:</span> <span class="p">(</span><span class="s1">&#39;</span><span class="si">%(asctime)s</span><span class="s1"> </span><span class="si">%(name)-15s</span><span class="s1"> &#39;</span>

  630.                     <span class="s1">&#39;</span><span class="si">%(levelname)-8s</span><span class="s1"> </span><span class="si">%(message)s</span><span class="s1">&#39;</span><span class="p">)}},</span>

  631. 

  632.  <span class="s1">&#39;handlers&#39;</span><span class="p">:</span> <span class="p">{</span><span class="s1">&#39;netlog&#39;</span><span class="p">:</span> <span class="p">{</span><span class="s1">&#39;backupCount&#39;</span><span class="p">:</span> <span class="mi">10</span><span class="p">,</span>

  633.                      <span class="s1">&#39;class&#39;</span><span class="p">:</span> <span class="s1">&#39;logging.handlers.RotatingFileHandler&#39;</span><span class="p">,</span>

  634.                      <span class="s1">&#39;filename&#39;</span><span class="p">:</span> <span class="s1">&#39;/logs/network.log&#39;</span><span class="p">,</span>

  635.                      <span class="s1">&#39;formatter&#39;</span><span class="p">:</span> <span class="s1">&#39;standard&#39;</span><span class="p">,</span>

  636.                      <span class="s1">&#39;level&#39;</span><span class="p">:</span> <span class="s1">&#39;INFO&#39;</span><span class="p">,</span>

  637.                      <span class="s1">&#39;maxBytes&#39;</span><span class="p">:</span> <span class="mi">1000000</span><span class="p">},</span>

  638.               <span class="s1">&#39;syslog&#39;</span><span class="p">:</span> <span class="p">{</span><span class="s1">&#39;class&#39;</span><span class="p">:</span> <span class="s1">&#39;logging.handlers.SysLogHandler&#39;</span><span class="p">,</span>

  639.                          <span class="s1">&#39;formatter&#39;</span><span class="p">:</span> <span class="s1">&#39;standard&#39;</span><span class="p">,</span>

  640.                          <span class="s1">&#39;level&#39;</span><span class="p">:</span> <span class="s1">&#39;ERROR&#39;</span><span class="p">}},</span>

  641. 

  642.  <span class="c1"># Specify all the subordinate loggers</span>

  643.  <span class="s1">&#39;loggers&#39;</span><span class="p">:</span> <span class="p">{</span>

  644.              <span class="s1">&#39;network&#39;</span><span class="p">:</span> <span class="p">{</span>

  645.                          <span class="s1">&#39;handlers&#39;</span><span class="p">:</span> <span class="p">[</span><span class="s1">&#39;netlog&#39;</span><span class="p">]</span>

  646.              <span class="p">}</span>

  647.  <span class="p">},</span>

  648.  <span class="c1"># Specify properties of the root logger</span>

  649.  <span class="s1">&#39;root&#39;</span><span class="p">:</span> <span class="p">{</span>

  650.           <span class="s1">&#39;handlers&#39;</span><span class="p">:</span> <span class="p">[</span><span class="s1">&#39;syslog&#39;</span><span class="p">]</span>

  651.  <span class="p">},</span>

  652. <span class="p">}</span>

  653. 

  654. <span class="c1"># Set up configuration</span>

  655. <span class="n">logging</span><span class="o">.</span><span class="n">config</span><span class="o">.</span><span class="n">dictConfig</span><span class="p">(</span><span class="n">configdict</span><span class="p">)</span>

  656. 

  657. <span class="c1"># As an example, log two error messages</span>

  658. <span class="n">logger</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="s1">&#39;/&#39;</span><span class="p">)</span>

  659. <span class="n">logger</span><span class="o">.</span><span class="n">error</span><span class="p">(</span><span class="s1">&#39;Database not found&#39;</span><span class="p">)</span>

  660. 

  661. <span class="n">netlogger</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="s1">&#39;network&#39;</span><span class="p">)</span>

  662. <span class="n">netlogger</span><span class="o">.</span><span class="n">error</span><span class="p">(</span><span class="s1">&#39;Connection failed&#39;</span><span class="p">)</span>

  663. </pre></div>

  664. </div>

  665. <p>Three smaller enhancements to the <a class="reference internal" href="../library/logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code></a> module, all

  666. implemented by Vinay Sajip, are:</p>

  667. <ul class="simple">

  668. <li><p>The <a class="reference internal" href="../library/logging.handlers.html#logging.handlers.SysLogHandler" title="logging.handlers.SysLogHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">SysLogHandler</span></code></a> class now supports

  669. syslogging over TCP.  The constructor has a <em>socktype</em> parameter

  670. giving the type of socket to use, either <a class="reference internal" href="../library/socket.html#socket.SOCK_DGRAM" title="socket.SOCK_DGRAM"><code class="xref py py-const docutils literal notranslate"><span class="pre">socket.SOCK_DGRAM</span></code></a>

  671. for UDP or <a class="reference internal" href="../library/socket.html#socket.SOCK_STREAM" title="socket.SOCK_STREAM"><code class="xref py py-const docutils literal notranslate"><span class="pre">socket.SOCK_STREAM</span></code></a> for TCP.  The default

  672. protocol remains UDP.</p></li>

  673. <li><p><a class="reference internal" href="../library/logging.html#logging.Logger" title="logging.Logger"><code class="xref py py-class docutils literal notranslate"><span class="pre">Logger</span></code></a> instances gained a <a class="reference internal" href="../library/logging.html#logging.Logger.getChild" title="logging.Logger.getChild"><code class="xref py py-meth docutils literal notranslate"><span class="pre">getChild()</span></code></a>

  674. method that retrieves a descendant logger using a relative path.

  675. For example, once you retrieve a logger by doing <code class="docutils literal notranslate"><span class="pre">log</span> <span class="pre">=</span> <span class="pre">getLogger('app')</span></code>,

  676. calling <code class="docutils literal notranslate"><span class="pre">log.getChild('network.listen')</span></code> is equivalent to

  677. <code class="docutils literal notranslate"><span class="pre">getLogger('app.network.listen')</span></code>.</p></li>

  678. <li><p>The <a class="reference internal" href="../library/logging.html#logging.LoggerAdapter" title="logging.LoggerAdapter"><code class="xref py py-class docutils literal notranslate"><span class="pre">LoggerAdapter</span></code></a> class gained an

  679. <a class="reference internal" href="../library/logging.html#logging.Logger.isEnabledFor" title="logging.Logger.isEnabledFor"><code class="xref py py-meth docutils literal notranslate"><span class="pre">isEnabledFor()</span></code></a> method that takes a

  680. <em>level</em> and returns whether the underlying logger would

  681. process a message of that level of importance.</p></li>

  682. </ul>

  683. <div class="admonition seealso">

  684. <p class="admonition-title">See also</p>

  685. <dl class="simple">

  686. <dt><span class="target" id="index-5"></span><a class="pep reference external" href="https://peps.python.org/pep-0391/"><strong>PEP 391</strong></a> - Dictionary-Based Configuration For Logging</dt><dd><p>PEP written and implemented by Vinay Sajip.</p>

  687. </dd>

  688. </dl>

  689. </div>

  690. </section>

  691. <section id="pep-3106-dictionary-views">

  692. <h2>PEP 3106: Dictionary Views<a class="headerlink" href="#pep-3106-dictionary-views" title="Link to this heading">¶</a></h2>

  693. <p>The dictionary methods <a class="reference internal" href="../library/stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal notranslate"><span class="pre">keys()</span></code></a>, <a class="reference internal" href="../library/stdtypes.html#dict.values" title="dict.values"><code class="xref py py-meth docutils literal notranslate"><span class="pre">values()</span></code></a>, and

  694. <a class="reference internal" href="../library/stdtypes.html#dict.items" title="dict.items"><code class="xref py py-meth docutils literal notranslate"><span class="pre">items()</span></code></a> are different in Python 3.x.  They return an object

  695. called a <em class="dfn">view</em> instead of a fully materialized list.</p>

  696. <p>It’s not possible to change the return values of <a class="reference internal" href="../library/stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal notranslate"><span class="pre">keys()</span></code></a>,

  697. <a class="reference internal" href="../library/stdtypes.html#dict.values" title="dict.values"><code class="xref py py-meth docutils literal notranslate"><span class="pre">values()</span></code></a>, and <a class="reference internal" href="../library/stdtypes.html#dict.items" title="dict.items"><code class="xref py py-meth docutils literal notranslate"><span class="pre">items()</span></code></a> in Python 2.7 because

  698. too much code would break.  Instead the 3.x versions were added

  699. under the new names <code class="xref py py-meth docutils literal notranslate"><span class="pre">viewkeys()</span></code>, <code class="xref py py-meth docutils literal notranslate"><span class="pre">viewvalues()</span></code>,

  700. and <code class="xref py py-meth docutils literal notranslate"><span class="pre">viewitems()</span></code>.</p>

  701. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">d</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">((</span><span class="n">i</span><span class="o">*</span><span class="mi">10</span><span class="p">,</span> <span class="nb">chr</span><span class="p">(</span><span class="mi">65</span><span class="o">+</span><span class="n">i</span><span class="p">))</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">26</span><span class="p">))</span>

  702. <span class="gp">&gt;&gt;&gt; </span><span class="n">d</span>

  703. <span class="go">{0: &#39;A&#39;, 130: &#39;N&#39;, 10: &#39;B&#39;, 140: &#39;O&#39;, 20: ..., 250: &#39;Z&#39;}</span>

  704. <span class="gp">&gt;&gt;&gt; </span><span class="n">d</span><span class="o">.</span><span class="n">viewkeys</span><span class="p">()</span>

  705. <span class="go">dict_keys([0, 130, 10, 140, 20, 150, 30, ..., 250])</span>

  706. </pre></div>

  707. </div>

  708. <p>Views can be iterated over, but the key and item views also behave

  709. like sets.  The <code class="docutils literal notranslate"><span class="pre">&amp;</span></code> operator performs intersection, and <code class="docutils literal notranslate"><span class="pre">|</span></code>

  710. performs a union:</p>

  711. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">d1</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">((</span><span class="n">i</span><span class="o">*</span><span class="mi">10</span><span class="p">,</span> <span class="nb">chr</span><span class="p">(</span><span class="mi">65</span><span class="o">+</span><span class="n">i</span><span class="p">))</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">26</span><span class="p">))</span>

  712. <span class="gp">&gt;&gt;&gt; </span><span class="n">d2</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">((</span><span class="n">i</span><span class="o">**</span><span class="mf">.5</span><span class="p">,</span> <span class="n">i</span><span class="p">)</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">1000</span><span class="p">))</span>

  713. <span class="gp">&gt;&gt;&gt; </span><span class="n">d1</span><span class="o">.</span><span class="n">viewkeys</span><span class="p">()</span> <span class="o">&amp;</span> <span class="n">d2</span><span class="o">.</span><span class="n">viewkeys</span><span class="p">()</span>

  714. <span class="go">set([0.0, 10.0, 20.0, 30.0])</span>

  715. <span class="gp">&gt;&gt;&gt; </span><span class="n">d1</span><span class="o">.</span><span class="n">viewkeys</span><span class="p">()</span> <span class="o">|</span> <span class="nb">range</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">30</span><span class="p">)</span>

  716. <span class="go">set([0, 1, 130, 3, 4, 5, 6, ..., 120, 250])</span>

  717. </pre></div>

  718. </div>

  719. <p>The view keeps track of the dictionary and its contents change as the

  720. dictionary is modified:</p>

  721. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">vk</span> <span class="o">=</span> <span class="n">d</span><span class="o">.</span><span class="n">viewkeys</span><span class="p">()</span>

  722. <span class="gp">&gt;&gt;&gt; </span><span class="n">vk</span>

  723. <span class="go">dict_keys([0, 130, 10, ..., 250])</span>

  724. <span class="gp">&gt;&gt;&gt; </span><span class="n">d</span><span class="p">[</span><span class="mi">260</span><span class="p">]</span> <span class="o">=</span> <span class="s1">&#39;&amp;&#39;</span>

  725. <span class="gp">&gt;&gt;&gt; </span><span class="n">vk</span>

  726. <span class="go">dict_keys([0, 130, 260, 10, ..., 250])</span>

  727. </pre></div>

  728. </div>

  729. <p>However, note that you can’t add or remove keys while you’re iterating

  730. over the view:</p>

  731. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">k</span> <span class="ow">in</span> <span class="n">vk</span><span class="p">:</span>

  732. <span class="gp">... </span>    <span class="n">d</span><span class="p">[</span><span class="n">k</span><span class="o">*</span><span class="mi">2</span><span class="p">]</span> <span class="o">=</span> <span class="n">k</span>

  733. <span class="gp">...</span>

  734. <span class="gt">Traceback (most recent call last):</span>

  735.   File <span class="nb">&quot;&lt;stdin&gt;&quot;</span>, line <span class="m">1</span>, in <span class="n">&lt;module&gt;</span>

  736. <span class="gr">RuntimeError</span>: <span class="n">dictionary changed size during iteration</span>

  737. </pre></div>

  738. </div>

  739. <p>You can use the view methods in Python 2.x code, and the 2to3

  740. converter will change them to the standard <a class="reference internal" href="../library/stdtypes.html#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal notranslate"><span class="pre">keys()</span></code></a>,

  741. <a class="reference internal" href="../library/stdtypes.html#dict.values" title="dict.values"><code class="xref py py-meth docutils literal notranslate"><span class="pre">values()</span></code></a>, and <a class="reference internal" href="../library/stdtypes.html#dict.items" title="dict.items"><code class="xref py py-meth docutils literal notranslate"><span class="pre">items()</span></code></a> methods.</p>

  742. <div class="admonition seealso">

  743. <p class="admonition-title">See also</p>

  744. <dl class="simple">

  745. <dt><span class="target" id="index-6"></span><a class="pep reference external" href="https://peps.python.org/pep-3106/"><strong>PEP 3106</strong></a> - Revamping dict.keys(), .values() and .items()</dt><dd><p>PEP written by Guido van Rossum.

  746. Backported to 2.7 by Alexandre Vassalotti; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1967">bpo-1967</a>.</p>

  747. </dd>

  748. </dl>

  749. </div>

  750. </section>

  751. <section id="pep-3137-the-memoryview-object">

  752. <h2>PEP 3137: The memoryview Object<a class="headerlink" href="#pep-3137-the-memoryview-object" title="Link to this heading">¶</a></h2>

  753. <p>The <a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> object provides a view of another object’s

  754. memory content that matches the <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> type’s interface.</p>

  755. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">string</span>

  756. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">string</span><span class="o">.</span><span class="n">letters</span><span class="p">)</span>

  757. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span>

  758. <span class="go">&lt;memory at 0x37f850&gt;</span>

  759. <span class="gp">&gt;&gt;&gt; </span><span class="nb">len</span><span class="p">(</span><span class="n">m</span><span class="p">)</span>           <span class="c1"># Returns length of underlying object</span>

  760. <span class="go">52</span>

  761. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="n">m</span><span class="p">[</span><span class="mi">25</span><span class="p">],</span> <span class="n">m</span><span class="p">[</span><span class="mi">26</span><span class="p">]</span>   <span class="c1"># Indexing returns one byte</span>

  762. <span class="go">(&#39;a&#39;, &#39;z&#39;, &#39;A&#39;)</span>

  763. <span class="gp">&gt;&gt;&gt; </span><span class="n">m2</span> <span class="o">=</span> <span class="n">m</span><span class="p">[</span><span class="mi">0</span><span class="p">:</span><span class="mi">26</span><span class="p">]</span>         <span class="c1"># Slicing returns another memoryview</span>

  764. <span class="gp">&gt;&gt;&gt; </span><span class="n">m2</span>

  765. <span class="go">&lt;memory at 0x37f080&gt;</span>

  766. </pre></div>

  767. </div>

  768. <p>The content of the view can be converted to a string of bytes or

  769. a list of integers:</p>

  770. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">m2</span><span class="o">.</span><span class="n">tobytes</span><span class="p">()</span>

  771. <span class="go">&#39;abcdefghijklmnopqrstuvwxyz&#39;</span>

  772. <span class="gp">&gt;&gt;&gt; </span><span class="n">m2</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span>

  773. <span class="go">[97, 98, 99, 100, 101, 102, 103, ... 121, 122]</span>

  774. <span class="gp">&gt;&gt;&gt;</span>

  775. </pre></div>

  776. </div>

  777. <p><a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> objects allow modifying the underlying object if

  778. it’s a mutable object.</p>

  779. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">m2</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="mi">75</span>

  780. <span class="gt">Traceback (most recent call last):</span>

  781.   File <span class="nb">&quot;&lt;stdin&gt;&quot;</span>, line <span class="m">1</span>, in <span class="n">&lt;module&gt;</span>

  782. <span class="gr">TypeError</span>: <span class="n">cannot modify read-only memory</span>

  783. <span class="gp">&gt;&gt;&gt; </span><span class="n">b</span> <span class="o">=</span> <span class="nb">bytearray</span><span class="p">(</span><span class="n">string</span><span class="o">.</span><span class="n">letters</span><span class="p">)</span>  <span class="c1"># Creating a mutable object</span>

  784. <span class="gp">&gt;&gt;&gt; </span><span class="n">b</span>

  785. <span class="go">bytearray(b&#39;abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ&#39;)</span>

  786. <span class="gp">&gt;&gt;&gt; </span><span class="n">mb</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">b</span><span class="p">)</span>

  787. <span class="gp">&gt;&gt;&gt; </span><span class="n">mb</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="s1">&#39;*&#39;</span>         <span class="c1"># Assign to view, changing the bytearray.</span>

  788. <span class="gp">&gt;&gt;&gt; </span><span class="n">b</span><span class="p">[</span><span class="mi">0</span><span class="p">:</span><span class="mi">5</span><span class="p">]</span>              <span class="c1"># The bytearray has been changed.</span>

  789. <span class="go">bytearray(b&#39;*bcde&#39;)</span>

  790. <span class="gp">&gt;&gt;&gt;</span>

  791. </pre></div>

  792. </div>

  793. <div class="admonition seealso">

  794. <p class="admonition-title">See also</p>

  795. <dl class="simple">

  796. <dt><span class="target" id="index-7"></span><a class="pep reference external" href="https://peps.python.org/pep-3137/"><strong>PEP 3137</strong></a> - Immutable Bytes and Mutable Buffer</dt><dd><p>PEP written by Guido van Rossum.

  797. Implemented by Travis Oliphant, Antoine Pitrou and others.

  798. Backported to 2.7 by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2396">bpo-2396</a>.</p>

  799. </dd>

  800. </dl>

  801. </div>

  802. </section>

  803. <section id="other-language-changes">

  804. <h2>Other Language Changes<a class="headerlink" href="#other-language-changes" title="Link to this heading">¶</a></h2>

  805. <p>Some smaller changes made to the core Python language are:</p>

  806. <ul>

  807. <li><p>The syntax for set literals has been backported from Python 3.x.

  808. Curly brackets are used to surround the contents of the resulting

  809. mutable set; set literals are

  810. distinguished from dictionaries by not containing colons and values.

  811. <code class="docutils literal notranslate"><span class="pre">{}</span></code> continues to represent an empty dictionary; use

  812. <code class="docutils literal notranslate"><span class="pre">set()</span></code> for an empty set.</p>

  813. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">}</span>

  814. <span class="go">set([1, 2, 3, 4, 5])</span>

  815. <span class="gp">&gt;&gt;&gt; </span><span class="nb">set</span><span class="p">()</span> <span class="c1"># empty set</span>

  816. <span class="go">set([])</span>

  817. <span class="gp">&gt;&gt;&gt; </span><span class="p">{}</span>    <span class="c1"># empty dict</span>

  818. <span class="go">{}</span>

  819. </pre></div>

  820. </div>

  821. <p>Backported by Alexandre Vassalotti; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2335">bpo-2335</a>.</p>

  822. </li>

  823. <li><p>Dictionary and set comprehensions are another feature backported from

  824. 3.x, generalizing list/generator comprehensions to use

  825. the literal syntax for sets and dictionaries.</p>

  826. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="p">{</span><span class="n">x</span><span class="p">:</span> <span class="n">x</span><span class="o">*</span><span class="n">x</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">6</span><span class="p">)}</span>

  827. <span class="go">{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25}</span>

  828. <span class="gp">&gt;&gt;&gt; </span><span class="p">{(</span><span class="s1">&#39;a&#39;</span><span class="o">*</span><span class="n">x</span><span class="p">)</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">6</span><span class="p">)}</span>

  829. <span class="go">set([&#39;&#39;, &#39;a&#39;, &#39;aa&#39;, &#39;aaa&#39;, &#39;aaaa&#39;, &#39;aaaaa&#39;])</span>

  830. </pre></div>

  831. </div>

  832. <p>Backported by Alexandre Vassalotti; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2333">bpo-2333</a>.</p>

  833. </li>

  834. <li><p>The <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement can now use multiple context managers

  835. in one statement.  Context managers are processed from left to right

  836. and each one is treated as beginning a new <code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code> statement.

  837. This means that:</p>

  838. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">with</span> <span class="n">A</span><span class="p">()</span> <span class="k">as</span> <span class="n">a</span><span class="p">,</span> <span class="n">B</span><span class="p">()</span> <span class="k">as</span> <span class="n">b</span><span class="p">:</span>

  839.     <span class="o">...</span> <span class="n">suite</span> <span class="n">of</span> <span class="n">statements</span> <span class="o">...</span>

  840. </pre></div>

  841. </div>

  842. <p>is equivalent to:</p>

  843. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">with</span> <span class="n">A</span><span class="p">()</span> <span class="k">as</span> <span class="n">a</span><span class="p">:</span>

  844.     <span class="k">with</span> <span class="n">B</span><span class="p">()</span> <span class="k">as</span> <span class="n">b</span><span class="p">:</span>

  845.         <span class="o">...</span> <span class="n">suite</span> <span class="n">of</span> <span class="n">statements</span> <span class="o">...</span>

  846. </pre></div>

  847. </div>

  848. <p>The <code class="xref py py-func docutils literal notranslate"><span class="pre">contextlib.nested()</span></code> function provides a very similar

  849. function, so it’s no longer necessary and has been deprecated.</p>

  850. <p>(Proposed in <a class="reference external" href="https://codereview.appspot.com/53094">https://codereview.appspot.com/53094</a>; implemented by

  851. Georg Brandl.)</p>

  852. </li>

  853. <li><p>Conversions between floating-point numbers and strings are

  854. now correctly rounded on most platforms.  These conversions occur

  855. in many different places: <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a> on

  856. floats and complex numbers; the <a class="reference internal" href="../library/functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> and <a class="reference internal" href="../library/functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate"><span class="pre">complex</span></code></a>

  857. constructors;

  858. numeric formatting; serializing and

  859. deserializing floats and complex numbers using the

  860. <a class="reference internal" href="../library/marshal.html#module-marshal" title="marshal: Convert Python objects to streams of bytes and back (with different constraints)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">marshal</span></code></a>, <a class="reference internal" href="../library/pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code></a>

  861. and <a class="reference internal" href="../library/json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json</span></code></a> modules;

  862. parsing of float and imaginary literals in Python code;

  863. and <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a>-to-float conversion.</p>

  864. <p>Related to this, the <a class="reference internal" href="../library/functions.html#repr" title="repr"><code class="xref py py-func docutils literal notranslate"><span class="pre">repr()</span></code></a> of a floating-point number <em>x</em>

  865. now returns a result based on the shortest decimal string that’s

  866. guaranteed to round back to <em>x</em> under correct rounding (with

  867. round-half-to-even rounding mode).  Previously it gave a string

  868. based on rounding x to 17 decimal digits.</p>

  869. <p>The rounding library responsible for this improvement works on

  870. Windows and on Unix platforms using the gcc, icc, or suncc

  871. compilers.  There may be a small number of platforms where correct

  872. operation of this code cannot be guaranteed, so the code is not

  873. used on such systems.  You can find out which code is being used

  874. by checking <a class="reference internal" href="../library/sys.html#sys.float_repr_style" title="sys.float_repr_style"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.float_repr_style</span></code></a>,  which will be <code class="docutils literal notranslate"><span class="pre">short</span></code>

  875. if the new code is in use and <code class="docutils literal notranslate"><span class="pre">legacy</span></code> if it isn’t.</p>

  876. <p>Implemented by Eric Smith and Mark Dickinson, using David Gay’s

  877. <code class="file docutils literal notranslate"><span class="pre">dtoa.c</span></code> library; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7117">bpo-7117</a>.</p>

  878. </li>

  879. <li><p>Conversions from long integers and regular integers to floating

  880. point now round differently, returning the floating-point number

  881. closest to the number.  This doesn’t matter for small integers that

  882. can be converted exactly, but for large numbers that will

  883. unavoidably lose precision, Python 2.7 now approximates more

  884. closely.  For example, Python 2.6 computed the following:</p>

  885. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">n</span> <span class="o">=</span> <span class="mi">295147905179352891391</span>

  886. <span class="gp">&gt;&gt;&gt; </span><span class="nb">float</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>

  887. <span class="go">2.9514790517935283e+20</span>

  888. <span class="gp">&gt;&gt;&gt; </span><span class="n">n</span> <span class="o">-</span> <span class="n">long</span><span class="p">(</span><span class="nb">float</span><span class="p">(</span><span class="n">n</span><span class="p">))</span>

  889. <span class="go">65535L</span>

  890. </pre></div>

  891. </div>

  892. <p>Python 2.7’s floating-point result is larger, but much closer to the

  893. true value:</p>

  894. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">n</span> <span class="o">=</span> <span class="mi">295147905179352891391</span>

  895. <span class="gp">&gt;&gt;&gt; </span><span class="nb">float</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>

  896. <span class="go">2.9514790517935289e+20</span>

  897. <span class="gp">&gt;&gt;&gt; </span><span class="n">n</span> <span class="o">-</span> <span class="n">long</span><span class="p">(</span><span class="nb">float</span><span class="p">(</span><span class="n">n</span><span class="p">))</span>

  898. <span class="go">-1L</span>

  899. </pre></div>

  900. </div>

  901. <p>(Implemented by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3166">bpo-3166</a>.)</p>

  902. <p>Integer division is also more accurate in its rounding behaviours.  (Also

  903. implemented by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1811">bpo-1811</a>.)</p>

  904. </li>

  905. <li><p>Implicit coercion for complex numbers has been removed; the interpreter

  906. will no longer ever attempt to call a <code class="xref py py-meth docutils literal notranslate"><span class="pre">__coerce__()</span></code> method on complex

  907. objects.  (Removed by Meador Inge and Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5211">bpo-5211</a>.)</p></li>

  908. <li><p>The <a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.format()</span></code></a> method now supports automatic numbering of the replacement

  909. fields.  This makes using <a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.format()</span></code></a> more closely resemble using

  910. <code class="docutils literal notranslate"><span class="pre">%s</span></code> formatting:</p>

  911. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="s1">&#39;</span><span class="si">{}</span><span class="s1">:</span><span class="si">{}</span><span class="s1">:</span><span class="si">{}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mi">2009</span><span class="p">,</span> <span class="mi">04</span><span class="p">,</span> <span class="s1">&#39;Sunday&#39;</span><span class="p">)</span>

  912. <span class="go">&#39;2009:4:Sunday&#39;</span>

  913. <span class="gp">&gt;&gt;&gt; </span><span class="s1">&#39;</span><span class="si">{}</span><span class="s1">:</span><span class="si">{}</span><span class="s1">:</span><span class="si">{day}</span><span class="s1">&#39;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mi">2009</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="n">day</span><span class="o">=</span><span class="s1">&#39;Sunday&#39;</span><span class="p">)</span>

  914. <span class="go">&#39;2009:4:Sunday&#39;</span>

  915. </pre></div>

  916. </div>

  917. <p>The auto-numbering takes the fields from left to right, so the first <code class="docutils literal notranslate"><span class="pre">{...}</span></code>

  918. specifier will use the first argument to <a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.format()</span></code></a>, the next

  919. specifier will use the next argument, and so on.  You can’t mix auto-numbering

  920. and explicit numbering – either number all of your specifier fields or none

  921. of them – but you can mix auto-numbering and named fields, as in the second

  922. example above.  (Contributed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5237">bpo-5237</a>.)</p>

  923. <p>Complex numbers now correctly support usage with <a class="reference internal" href="../library/functions.html#format" title="format"><code class="xref py py-func docutils literal notranslate"><span class="pre">format()</span></code></a>,

  924. and default to being right-aligned.

  925. Specifying a precision or comma-separation applies to both the real

  926. and imaginary parts of the number, but a specified field width and

  927. alignment is applied to the whole of the resulting <code class="docutils literal notranslate"><span class="pre">1.5+3j</span></code>

  928. output.  (Contributed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1588">bpo-1588</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7988">bpo-7988</a>.)</p>

  929. <p>The ‘F’ format code now always formats its output using uppercase characters,

  930. so it will now produce ‘INF’ and ‘NAN’.

  931. (Contributed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3382">bpo-3382</a>.)</p>

  932. <p>A low-level change: the <a class="reference internal" href="../reference/datamodel.html#object.__format__" title="object.__format__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">object.__format__()</span></code></a> method now triggers

  933. a <a class="reference internal" href="../library/exceptions.html#PendingDeprecationWarning" title="PendingDeprecationWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">PendingDeprecationWarning</span></code></a> if it’s passed a format string,

  934. because the <code class="xref py py-meth docutils literal notranslate"><span class="pre">__format__()</span></code> method for <a class="reference internal" href="../library/functions.html#object" title="object"><code class="xref py py-class docutils literal notranslate"><span class="pre">object</span></code></a> converts

  935. the object to a string representation and formats that.  Previously

  936. the method silently applied the format string to the string

  937. representation, but that could hide mistakes in Python code.  If

  938. you’re supplying formatting information such as an alignment or

  939. precision, presumably you’re expecting the formatting to be applied

  940. in some object-specific way.  (Fixed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7994">bpo-7994</a>.)</p>

  941. </li>

  942. <li><p>The <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-func docutils literal notranslate"><span class="pre">int()</span></code></a> and <code class="xref py py-func docutils literal notranslate"><span class="pre">long()</span></code> types gained a <code class="docutils literal notranslate"><span class="pre">bit_length</span></code>

  943. method that returns the number of bits necessary to represent

  944. its argument in binary:</p>

  945. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">n</span> <span class="o">=</span> <span class="mi">37</span>

  946. <span class="gp">&gt;&gt;&gt; </span><span class="nb">bin</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>

  947. <span class="go">&#39;0b100101&#39;</span>

  948. <span class="gp">&gt;&gt;&gt; </span><span class="n">n</span><span class="o">.</span><span class="n">bit_length</span><span class="p">()</span>

  949. <span class="go">6</span>

  950. <span class="gp">&gt;&gt;&gt; </span><span class="n">n</span> <span class="o">=</span> <span class="mi">2</span><span class="o">**</span><span class="mi">123</span><span class="o">-</span><span class="mi">1</span>

  951. <span class="gp">&gt;&gt;&gt; </span><span class="n">n</span><span class="o">.</span><span class="n">bit_length</span><span class="p">()</span>

  952. <span class="go">123</span>

  953. <span class="gp">&gt;&gt;&gt; </span><span class="p">(</span><span class="n">n</span><span class="o">+</span><span class="mi">1</span><span class="p">)</span><span class="o">.</span><span class="n">bit_length</span><span class="p">()</span>

  954. <span class="go">124</span>

  955. </pre></div>

  956. </div>

  957. <p>(Contributed by Fredrik Johansson and Victor Stinner; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3439">bpo-3439</a>.)</p>

  958. </li>

  959. <li><p>The <a class="reference internal" href="../reference/simple_stmts.html#import"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">import</span></code></a> statement will no longer try an absolute import

  960. if a relative import (e.g. <code class="docutils literal notranslate"><span class="pre">from</span> <span class="pre">.os</span> <span class="pre">import</span> <span class="pre">sep</span></code>) fails.  This

  961. fixes a bug, but could possibly break certain <code class="xref std std-keyword docutils literal notranslate"><span class="pre">import</span></code>

  962. statements that were only working by accident.  (Fixed by Meador Inge;

  963. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7902">bpo-7902</a>.)</p></li>

  964. <li><p>It’s now possible for a subclass of the built-in <code class="xref py py-class docutils literal notranslate"><span class="pre">unicode</span></code> type

  965. to override the <code class="xref py py-meth docutils literal notranslate"><span class="pre">__unicode__()</span></code> method.  (Implemented by

  966. Victor Stinner; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1583863">bpo-1583863</a>.)</p></li>

  967. <li><p>The <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> type’s <a class="reference internal" href="../library/stdtypes.html#bytearray.translate" title="bytearray.translate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">translate()</span></code></a> method now accepts

  968. <code class="docutils literal notranslate"><span class="pre">None</span></code> as its first argument.  (Fixed by Georg Brandl;

  969. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4759">bpo-4759</a>.)</p>

  970. </li>

  971. <li><p>When using <a class="reference internal" href="../library/functions.html#classmethod" title="classmethod"><code class="xref py py-class docutils literal notranslate"><span class="pre">&#64;classmethod</span></code></a> and

  972. <a class="reference internal" href="../library/functions.html#staticmethod" title="staticmethod"><code class="xref py py-class docutils literal notranslate"><span class="pre">&#64;staticmethod</span></code></a> to wrap

  973. methods as class or static methods, the wrapper object now

  974. exposes the wrapped function as their <a class="reference internal" href="../reference/datamodel.html#method.__func__" title="method.__func__"><code class="xref py py-attr docutils literal notranslate"><span class="pre">__func__</span></code></a>

  975. attribute.

  976. (Contributed by Amaury Forgeot d’Arc, after a suggestion by

  977. George Sakkis; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5982">bpo-5982</a>.)</p></li>

  978. <li><p>When a restricted set of attributes were set using <code class="docutils literal notranslate"><span class="pre">__slots__</span></code>,

  979. deleting an unset attribute would not raise <a class="reference internal" href="../library/exceptions.html#AttributeError" title="AttributeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">AttributeError</span></code></a>

  980. as you would expect.  Fixed by Benjamin Peterson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7604">bpo-7604</a>.)</p></li>

  981. <li><p>Two new encodings are now supported: “cp720”, used primarily for

  982. Arabic text; and “cp858”, a variant of CP 850 that adds the euro

  983. symbol.  (CP720 contributed by Alexander Belchenko and Amaury

  984. Forgeot d’Arc in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1616979">bpo-1616979</a>; CP858 contributed by Tim Hatch in

  985. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8016">bpo-8016</a>.)</p></li>

  986. <li><p>The <code class="xref py py-class docutils literal notranslate"><span class="pre">file</span></code> object will now set the <code class="xref py py-attr docutils literal notranslate"><span class="pre">filename</span></code> attribute

  987. on the <a class="reference internal" href="../library/exceptions.html#IOError" title="IOError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">IOError</span></code></a> exception when trying to open a directory

  988. on POSIX platforms (noted by Jan Kaliszewski; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4764">bpo-4764</a>), and

  989. now explicitly checks for and forbids writing to read-only file objects

  990. instead of trusting the C library to catch and report the error

  991. (fixed by Stefan Krah; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5677">bpo-5677</a>).</p></li>

  992. <li><p>The Python tokenizer now translates line endings itself, so the

  993. <a class="reference internal" href="../library/functions.html#compile" title="compile"><code class="xref py py-func docutils literal notranslate"><span class="pre">compile()</span></code></a> built-in function now accepts code using any

  994. line-ending convention.  Additionally, it no longer requires that the

  995. code end in a newline.</p></li>

  996. <li><p>Extra parentheses in function definitions are illegal in Python 3.x,

  997. meaning that you get a syntax error from <code class="docutils literal notranslate"><span class="pre">def</span> <span class="pre">f((x)):</span> <span class="pre">pass</span></code>.  In

  998. Python3-warning mode, Python 2.7 will now warn about this odd usage.

  999. (Noted by James Lingard; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7362">bpo-7362</a>.)</p></li>

  1000. <li><p>It’s now possible to create weak references to old-style class

  1001. objects.  New-style classes were always weak-referenceable.  (Fixed

  1002. by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8268">bpo-8268</a>.)</p></li>

  1003. <li><p>When a module object is garbage-collected, the module’s dictionary is

  1004. now only cleared if no one else is holding a reference to the

  1005. dictionary (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7140">bpo-7140</a>).</p></li>

  1006. </ul>

  1007. <section id="interpreter-changes">

  1008. <span id="new-27-interpreter"></span><h3>Interpreter Changes<a class="headerlink" href="#interpreter-changes" title="Link to this heading">¶</a></h3>

  1009. <p>A new environment variable, <span class="target" id="index-8"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONWARNINGS"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONWARNINGS</span></code></a>,

  1010. allows controlling warnings.  It should be set to a string

  1011. containing warning settings, equivalent to those

  1012. used with the <a class="reference internal" href="../using/cmdline.html#cmdoption-W"><code class="xref std std-option docutils literal notranslate"><span class="pre">-W</span></code></a> switch, separated by commas.

  1013. (Contributed by Brian Curtin; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7301">bpo-7301</a>.)</p>

  1014. <p>For example, the following setting will print warnings every time

  1015. they occur, but turn warnings from the <a class="reference internal" href="../library/http.cookies.html#module-http.cookies" title="http.cookies: Support for HTTP state management (cookies)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">Cookie</span></code></a> module into an

  1016. error.  (The exact syntax for setting an environment variable varies

  1017. across operating systems and shells.)</p>

  1018. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">export</span> <span class="n">PYTHONWARNINGS</span><span class="o">=</span><span class="nb">all</span><span class="p">,</span><span class="n">error</span><span class="p">:::</span><span class="n">Cookie</span><span class="p">:</span><span class="mi">0</span>

  1019. </pre></div>

  1020. </div>

  1021. </section>

  1022. <section id="optimizations">

  1023. <h3>Optimizations<a class="headerlink" href="#optimizations" title="Link to this heading">¶</a></h3>

  1024. <p>Several performance enhancements have been added:</p>

  1025. <ul>

  1026. <li><p>A new opcode was added to perform the initial setup for

  1027. <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statements, looking up the <a class="reference internal" href="../reference/datamodel.html#object.__enter__" title="object.__enter__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__enter__()</span></code></a> and

  1028. <a class="reference internal" href="../reference/datamodel.html#object.__exit__" title="object.__exit__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__exit__()</span></code></a> methods.  (Contributed by Benjamin Peterson.)</p></li>

  1029. <li><p>The garbage collector now performs better for one common usage

  1030. pattern: when many objects are being allocated without deallocating

  1031. any of them.  This would previously take quadratic

  1032. time for garbage collection, but now the number of full garbage collections

  1033. is reduced as the number of objects on the heap grows.

  1034. The new logic only performs a full garbage collection pass when

  1035. the middle generation has been collected 10 times and when the

  1036. number of survivor objects from the middle generation exceeds 10% of

  1037. the number of objects in the oldest generation.  (Suggested by Martin

  1038. von Löwis and implemented by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4074">bpo-4074</a>.)</p></li>

  1039. <li><p>The garbage collector tries to avoid tracking simple containers

  1040. which can’t be part of a cycle. In Python 2.7, this is now true for

  1041. tuples and dicts containing atomic types (such as ints, strings,

  1042. etc.). Transitively, a dict containing tuples of atomic types won’t

  1043. be tracked either. This helps reduce the cost of each

  1044. garbage collection by decreasing the number of objects to be

  1045. considered and traversed by the collector.

  1046. (Contributed by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4688">bpo-4688</a>.)</p></li>

  1047. <li><p>Long integers are now stored internally either in base <code class="docutils literal notranslate"><span class="pre">2**15</span></code> or in base

  1048. <code class="docutils literal notranslate"><span class="pre">2**30</span></code>, the base being determined at build time.  Previously, they

  1049. were always stored in base <code class="docutils literal notranslate"><span class="pre">2**15</span></code>.  Using base <code class="docutils literal notranslate"><span class="pre">2**30</span></code> gives

  1050. significant performance improvements on 64-bit machines, but

  1051. benchmark results on 32-bit machines have been mixed.  Therefore,

  1052. the default is to use base <code class="docutils literal notranslate"><span class="pre">2**30</span></code> on 64-bit machines and base <code class="docutils literal notranslate"><span class="pre">2**15</span></code>

  1053. on 32-bit machines; on Unix, there’s a new configure option

  1054. <code class="xref std std-option docutils literal notranslate"><span class="pre">--enable-big-digits</span></code> that can be used to override this default.</p>

  1055. <p>Apart from the performance improvements this change should be

  1056. invisible to end users, with one exception: for testing and

  1057. debugging purposes there’s a new structseq <code class="xref py py-data docutils literal notranslate"><span class="pre">sys.long_info</span></code> that

  1058. provides information about the internal format, giving the number of

  1059. bits per digit and the size in bytes of the C type used to store

  1060. each digit:</p>

  1061. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">sys</span>

  1062. <span class="gp">&gt;&gt;&gt; </span><span class="n">sys</span><span class="o">.</span><span class="n">long_info</span>

  1063. <span class="go">sys.long_info(bits_per_digit=30, sizeof_digit=4)</span>

  1064. </pre></div>

  1065. </div>

  1066. <p>(Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4258">bpo-4258</a>.)</p>

  1067. <p>Another set of changes made long objects a few bytes smaller: 2 bytes

  1068. smaller on 32-bit systems and 6 bytes on 64-bit.

  1069. (Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5260">bpo-5260</a>.)</p>

  1070. </li>

  1071. <li><p>The division algorithm for long integers has been made faster

  1072. by tightening the inner loop, doing shifts instead of multiplications,

  1073. and fixing an unnecessary extra iteration.

  1074. Various benchmarks show speedups of between 50% and 150% for long

  1075. integer divisions and modulo operations.

  1076. (Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5512">bpo-5512</a>.)

  1077. Bitwise operations are also significantly faster (initial patch by

  1078. Gregory Smith; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1087418">bpo-1087418</a>).</p></li>

  1079. <li><p>The implementation of <code class="docutils literal notranslate"><span class="pre">%</span></code> checks for the left-side operand being

  1080. a Python string and special-cases it; this results in a 1–3%

  1081. performance increase for applications that frequently use <code class="docutils literal notranslate"><span class="pre">%</span></code>

  1082. with strings, such as templating libraries.

  1083. (Implemented by Collin Winter; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5176">bpo-5176</a>.)</p></li>

  1084. <li><p>List comprehensions with an <code class="docutils literal notranslate"><span class="pre">if</span></code> condition are compiled into

  1085. faster bytecode.  (Patch by Antoine Pitrou, back-ported to 2.7

  1086. by Jeffrey Yasskin; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4715">bpo-4715</a>.)</p></li>

  1087. <li><p>Converting an integer or long integer to a decimal string was made

  1088. faster by special-casing base 10 instead of using a generalized

  1089. conversion function that supports arbitrary bases.

  1090. (Patch by Gawain Bolton; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6713">bpo-6713</a>.)</p></li>

  1091. <li><p>The <code class="xref py py-meth docutils literal notranslate"><span class="pre">split()</span></code>, <code class="xref py py-meth docutils literal notranslate"><span class="pre">replace()</span></code>, <code class="xref py py-meth docutils literal notranslate"><span class="pre">rindex()</span></code>,

  1092. <code class="xref py py-meth docutils literal notranslate"><span class="pre">rpartition()</span></code>, and <code class="xref py py-meth docutils literal notranslate"><span class="pre">rsplit()</span></code> methods of string-like types

  1093. (strings, Unicode strings, and <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> objects) now use a

  1094. fast reverse-search algorithm instead of a character-by-character

  1095. scan.  This is sometimes faster by a factor of 10.  (Added by

  1096. Florent Xicluna; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7462">bpo-7462</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7622">bpo-7622</a>.)</p></li>

  1097. <li><p>The <a class="reference internal" href="../library/pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code></a> and <code class="xref py py-mod docutils literal notranslate"><span class="pre">cPickle</span></code> modules now automatically

  1098. intern the strings used for attribute names, reducing memory usage

  1099. of the objects resulting from unpickling.  (Contributed by Jake

  1100. McGuire; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5084">bpo-5084</a>.)</p></li>

  1101. <li><p>The <code class="xref py py-mod docutils literal notranslate"><span class="pre">cPickle</span></code> module now special-cases dictionaries,

  1102. nearly halving the time required to pickle them.

  1103. (Contributed by Collin Winter; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5670">bpo-5670</a>.)</p></li>

  1104. </ul>

  1105. </section>

  1106. </section>

  1107. <section id="new-and-improved-modules">

  1108. <h2>New and Improved Modules<a class="headerlink" href="#new-and-improved-modules" title="Link to this heading">¶</a></h2>

  1109. <p>As in every release, Python’s standard library received a number of

  1110. enhancements and bug fixes.  Here’s a partial list of the most notable

  1111. changes, sorted alphabetically by module name. Consult the

  1112. <code class="file docutils literal notranslate"><span class="pre">Misc/NEWS</span></code> file in the source tree for a more complete list of

  1113. changes, or look through the Subversion logs for all the details.</p>

  1114. <ul>

  1115. <li><p>The <a class="reference internal" href="../library/bdb.html#module-bdb" title="bdb: Debugger framework."><code class="xref py py-mod docutils literal notranslate"><span class="pre">bdb</span></code></a> module’s base debugging class <a class="reference internal" href="../library/bdb.html#bdb.Bdb" title="bdb.Bdb"><code class="xref py py-class docutils literal notranslate"><span class="pre">Bdb</span></code></a>

  1116. gained a feature for skipping modules.  The constructor

  1117. now takes an iterable containing glob-style patterns such as

  1118. <code class="docutils literal notranslate"><span class="pre">django.*</span></code>; the debugger will not step into stack frames

  1119. from a module that matches one of these patterns.

  1120. (Contributed by Maru Newby after a suggestion by

  1121. Senthil Kumaran; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5142">bpo-5142</a>.)</p></li>

  1122. <li><p>The <a class="reference internal" href="../library/binascii.html#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">binascii</span></code></a> module now supports the buffer API, so it can be

  1123. used with <a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> instances and other similar buffer objects.

  1124. (Backported from 3.x by Florent Xicluna; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7703">bpo-7703</a>.)</p></li>

  1125. <li><p>Updated module: the <code class="xref py py-mod docutils literal notranslate"><span class="pre">bsddb</span></code> module has been updated from 4.7.2devel9

  1126. to version 4.8.4 of

  1127. <a class="reference external" href="https://www.jcea.es/programacion/pybsddb.htm">the pybsddb package</a>.

  1128. The new version features better Python 3.x compatibility, various bug fixes,

  1129. and adds several new BerkeleyDB flags and methods.

  1130. (Updated by Jesús Cea Avión; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8156">bpo-8156</a>.  The pybsddb

  1131. changelog can be read at <a class="reference external" href="https://hg.jcea.es/pybsddb/file/tip/ChangeLog">https://hg.jcea.es/pybsddb/file/tip/ChangeLog</a>.)</p></li>

  1132. <li><p>The <a class="reference internal" href="../library/bz2.html#module-bz2" title="bz2: Interfaces for bzip2 compression and decompression."><code class="xref py py-mod docutils literal notranslate"><span class="pre">bz2</span></code></a> module’s <a class="reference internal" href="../library/bz2.html#bz2.BZ2File" title="bz2.BZ2File"><code class="xref py py-class docutils literal notranslate"><span class="pre">BZ2File</span></code></a> now supports the context

  1133. management protocol, so you can write <code class="docutils literal notranslate"><span class="pre">with</span> <span class="pre">bz2.BZ2File(...)</span> <span class="pre">as</span> <span class="pre">f:</span></code>.

  1134. (Contributed by Hagen Fürstenau; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3860">bpo-3860</a>.)</p></li>

  1135. <li><p>New class: the <a class="reference internal" href="../library/collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Counter</span></code></a> class in the <a class="reference internal" href="../library/collections.html#module-collections" title="collections: Container datatypes"><code class="xref py py-mod docutils literal notranslate"><span class="pre">collections</span></code></a>

  1136. module is useful for tallying data.  <a class="reference internal" href="../library/collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Counter</span></code></a> instances

  1137. behave mostly like dictionaries but return zero for missing keys instead of

  1138. raising a <a class="reference internal" href="../library/exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a>:</p>

  1139. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">collections</span> <span class="kn">import</span> <span class="n">Counter</span>

  1140. <span class="gp">&gt;&gt;&gt; </span><span class="n">c</span> <span class="o">=</span> <span class="n">Counter</span><span class="p">()</span>

  1141. <span class="gp">&gt;&gt;&gt; </span><span class="k">for</span> <span class="n">letter</span> <span class="ow">in</span> <span class="s1">&#39;here is a sample of english text&#39;</span><span class="p">:</span>

  1142. <span class="gp">... </span>  <span class="n">c</span><span class="p">[</span><span class="n">letter</span><span class="p">]</span> <span class="o">+=</span> <span class="mi">1</span>

  1143. <span class="gp">...</span>

  1144. <span class="gp">&gt;&gt;&gt; </span><span class="n">c</span> 

  1145. <span class="go">Counter({&#39; &#39;: 6, &#39;e&#39;: 5, &#39;s&#39;: 3, &#39;a&#39;: 2, &#39;i&#39;: 2, &#39;h&#39;: 2,</span>

  1146. <span class="go">&#39;l&#39;: 2, &#39;t&#39;: 2, &#39;g&#39;: 1, &#39;f&#39;: 1, &#39;m&#39;: 1, &#39;o&#39;: 1, &#39;n&#39;: 1,</span>

  1147. <span class="go">&#39;p&#39;: 1, &#39;r&#39;: 1, &#39;x&#39;: 1})</span>

  1148. <span class="gp">&gt;&gt;&gt; </span><span class="n">c</span><span class="p">[</span><span class="s1">&#39;e&#39;</span><span class="p">]</span>

  1149. <span class="go">5</span>

  1150. <span class="gp">&gt;&gt;&gt; </span><span class="n">c</span><span class="p">[</span><span class="s1">&#39;z&#39;</span><span class="p">]</span>

  1151. <span class="go">0</span>

  1152. </pre></div>

  1153. </div>

  1154. <p>There are three additional <a class="reference internal" href="../library/collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Counter</span></code></a> methods.

  1155. <a class="reference internal" href="../library/collections.html#collections.Counter.most_common" title="collections.Counter.most_common"><code class="xref py py-meth docutils literal notranslate"><span class="pre">most_common()</span></code></a> returns the N most common

  1156. elements and their counts.  <a class="reference internal" href="../library/collections.html#collections.Counter.elements" title="collections.Counter.elements"><code class="xref py py-meth docutils literal notranslate"><span class="pre">elements()</span></code></a>

  1157. returns an iterator over the contained elements, repeating each

  1158. element as many times as its count.

  1159. <a class="reference internal" href="../library/collections.html#collections.Counter.subtract" title="collections.Counter.subtract"><code class="xref py py-meth docutils literal notranslate"><span class="pre">subtract()</span></code></a> takes an iterable and

  1160. subtracts one for each element instead of adding; if the argument is

  1161. a dictionary or another <code class="xref py py-class docutils literal notranslate"><span class="pre">Counter</span></code>, the counts are

  1162. subtracted.</p>

  1163. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">c</span><span class="o">.</span><span class="n">most_common</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span>

  1164. <span class="go">[(&#39; &#39;, 6), (&#39;e&#39;, 5), (&#39;s&#39;, 3), (&#39;a&#39;, 2), (&#39;i&#39;, 2)]</span>

  1165. <span class="gp">&gt;&gt;&gt; </span><span class="n">c</span><span class="o">.</span><span class="n">elements</span><span class="p">()</span> <span class="o">-&gt;</span>

  1166. <span class="go">   &#39;a&#39;, &#39;a&#39;, &#39; &#39;, &#39; &#39;, &#39; &#39;, &#39; &#39;, &#39; &#39;, &#39; &#39;,</span>

  1167. <span class="go">   &#39;e&#39;, &#39;e&#39;, &#39;e&#39;, &#39;e&#39;, &#39;e&#39;, &#39;g&#39;, &#39;f&#39;, &#39;i&#39;, &#39;i&#39;,</span>

  1168. <span class="go">   &#39;h&#39;, &#39;h&#39;, &#39;m&#39;, &#39;l&#39;, &#39;l&#39;, &#39;o&#39;, &#39;n&#39;, &#39;p&#39;, &#39;s&#39;,</span>

  1169. <span class="go">   &#39;s&#39;, &#39;s&#39;, &#39;r&#39;, &#39;t&#39;, &#39;t&#39;, &#39;x&#39;</span>

  1170. <span class="gp">&gt;&gt;&gt; </span><span class="n">c</span><span class="p">[</span><span class="s1">&#39;e&#39;</span><span class="p">]</span>

  1171. <span class="go">5</span>

  1172. <span class="gp">&gt;&gt;&gt; </span><span class="n">c</span><span class="o">.</span><span class="n">subtract</span><span class="p">(</span><span class="s1">&#39;very heavy on the letter e&#39;</span><span class="p">)</span>

  1173. <span class="gp">&gt;&gt;&gt; </span><span class="n">c</span><span class="p">[</span><span class="s1">&#39;e&#39;</span><span class="p">]</span>    <span class="c1"># Count is now lower</span>

  1174. <span class="go">-1</span>

  1175. </pre></div>

  1176. </div>

  1177. <p>Contributed by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1696199">bpo-1696199</a>.</p>

  1178. <p>New class: <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">OrderedDict</span></code></a> is described in the earlier

  1179. section <a class="reference internal" href="#pep-0372"><span class="std std-ref">PEP 372: Adding an Ordered Dictionary to collections</span></a>.</p>

  1180. <p>New method: The <a class="reference internal" href="../library/collections.html#collections.deque" title="collections.deque"><code class="xref py py-class docutils literal notranslate"><span class="pre">deque</span></code></a> data type now has a

  1181. <a class="reference internal" href="../library/collections.html#collections.deque.count" title="collections.deque.count"><code class="xref py py-meth docutils literal notranslate"><span class="pre">count()</span></code></a> method that returns the number of

  1182. contained elements equal to the supplied argument <em>x</em>, and a

  1183. <a class="reference internal" href="../library/collections.html#collections.deque.reverse" title="collections.deque.reverse"><code class="xref py py-meth docutils literal notranslate"><span class="pre">reverse()</span></code></a> method that reverses the elements

  1184. of the deque in-place.  <a class="reference internal" href="../library/collections.html#collections.deque" title="collections.deque"><code class="xref py py-class docutils literal notranslate"><span class="pre">deque</span></code></a> also exposes its maximum

  1185. length as the read-only <a class="reference internal" href="../library/collections.html#collections.deque.maxlen" title="collections.deque.maxlen"><code class="xref py py-attr docutils literal notranslate"><span class="pre">maxlen</span></code></a> attribute.

  1186. (Both features added by Raymond Hettinger.)</p>

  1187. <p>The <a class="reference internal" href="../library/collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-class docutils literal notranslate"><span class="pre">namedtuple</span></code></a> class now has an optional <em>rename</em> parameter.

  1188. If <em>rename</em> is true, field names that are invalid because they’ve

  1189. been repeated or aren’t legal Python identifiers will be

  1190. renamed to legal names that are derived from the field’s

  1191. position within the list of fields:</p>

  1192. <div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">collections</span> <span class="kn">import</span> <span class="n">namedtuple</span>

  1193. <span class="gp">&gt;&gt;&gt; </span><span class="n">T</span> <span class="o">=</span> <span class="n">namedtuple</span><span class="p">(</span><span class="s1">&#39;T&#39;</span><span class="p">,</span> <span class="p">[</span><span class="s1">&#39;field1&#39;</span><span class="p">,</span> <span class="s1">&#39;$illegal&#39;</span><span class="p">,</span> <span class="s1">&#39;for&#39;</span><span class="p">,</span> <span class="s1">&#39;field2&#39;</span><span class="p">],</span> <span class="n">rename</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  1194. <span class="gp">&gt;&gt;&gt; </span><span class="n">T</span><span class="o">.</span><span class="n">_fields</span>

  1195. <span class="go">(&#39;field1&#39;, &#39;_1&#39;, &#39;_2&#39;, &#39;field2&#39;)</span>

  1196. </pre></div>

  1197. </div>

  1198. <p>(Added by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1818">bpo-1818</a>.)</p>

  1199. <p>Finally, the <a class="reference internal" href="../library/collections.abc.html#collections.abc.Mapping" title="collections.abc.Mapping"><code class="xref py py-class docutils literal notranslate"><span class="pre">Mapping</span></code></a> abstract base class now

  1200. returns <a class="reference internal" href="../library/constants.html#NotImplemented" title="NotImplemented"><code class="xref py py-data docutils literal notranslate"><span class="pre">NotImplemented</span></code></a> if a mapping is compared to

  1201. another type that isn’t a <code class="xref py py-class docutils literal notranslate"><span class="pre">Mapping</span></code>.

  1202. (Fixed by Daniel Stutzbach; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8729">bpo-8729</a>.)</p>

  1203. </li>

  1204. <li><p>Constructors for the parsing classes in the <a class="reference internal" href="../library/configparser.html#module-configparser" title="configparser: Configuration file parser."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ConfigParser</span></code></a> module now

  1205. take an <em>allow_no_value</em> parameter, defaulting to false; if true,

  1206. options without values will be allowed.  For example:</p>

  1207. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">ConfigParser</span><span class="o">,</span> <span class="nn">StringIO</span>

  1208. <span class="gp">&gt;&gt;&gt; </span><span class="n">sample_config</span> <span class="o">=</span> <span class="s2">&quot;&quot;&quot;</span>

  1209. <span class="gp">... </span><span class="s2">[mysqld]</span>

  1210. <span class="gp">... </span><span class="s2">user = mysql</span>

  1211. <span class="gp">... </span><span class="s2">pid-file = /var/run/mysqld/mysqld.pid</span>

  1212. <span class="gp">... </span><span class="s2">skip-bdb</span>

  1213. <span class="gp">... </span><span class="s2">&quot;&quot;&quot;</span>

  1214. <span class="gp">&gt;&gt;&gt; </span><span class="n">config</span> <span class="o">=</span> <span class="n">ConfigParser</span><span class="o">.</span><span class="n">RawConfigParser</span><span class="p">(</span><span class="n">allow_no_value</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  1215. <span class="gp">&gt;&gt;&gt; </span><span class="n">config</span><span class="o">.</span><span class="n">readfp</span><span class="p">(</span><span class="n">StringIO</span><span class="o">.</span><span class="n">StringIO</span><span class="p">(</span><span class="n">sample_config</span><span class="p">))</span>

  1216. <span class="gp">&gt;&gt;&gt; </span><span class="n">config</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s1">&#39;mysqld&#39;</span><span class="p">,</span> <span class="s1">&#39;user&#39;</span><span class="p">)</span>

  1217. <span class="go">&#39;mysql&#39;</span>

  1218. <span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span> <span class="n">config</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s1">&#39;mysqld&#39;</span><span class="p">,</span> <span class="s1">&#39;skip-bdb&#39;</span><span class="p">)</span>

  1219. <span class="go">None</span>

  1220. <span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span> <span class="n">config</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s1">&#39;mysqld&#39;</span><span class="p">,</span> <span class="s1">&#39;unknown&#39;</span><span class="p">)</span>

  1221. <span class="gt">Traceback (most recent call last):</span>

  1222. <span class="w">  </span><span class="c">...</span>

  1223. <span class="gr">NoOptionError</span>: <span class="n">No option &#39;unknown&#39; in section: &#39;mysqld&#39;</span>

  1224. </pre></div>

  1225. </div>

  1226. <p>(Contributed by Mats Kindahl; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7005">bpo-7005</a>.)</p>

  1227. </li>

  1228. <li><p>Deprecated function: <code class="xref py py-func docutils literal notranslate"><span class="pre">contextlib.nested()</span></code>, which allows

  1229. handling more than one context manager with a single <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a>

  1230. statement, has been deprecated, because the <code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code> statement

  1231. now supports multiple context managers.</p></li>

  1232. <li><p>The <a class="reference internal" href="../library/http.cookiejar.html#module-http.cookiejar" title="http.cookiejar: Classes for automatic handling of HTTP cookies."><code class="xref py py-mod docutils literal notranslate"><span class="pre">cookielib</span></code></a> module now ignores cookies that have an invalid

  1233. version field, one that doesn’t contain an integer value.  (Fixed by

  1234. John J. Lee; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3924">bpo-3924</a>.)</p></li>

  1235. <li><p>The <a class="reference internal" href="../library/copy.html#module-copy" title="copy: Shallow and deep copy operations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">copy</span></code></a> module’s <a class="reference internal" href="../library/copy.html#copy.deepcopy" title="copy.deepcopy"><code class="xref py py-func docutils literal notranslate"><span class="pre">deepcopy()</span></code></a> function will now

  1236. correctly copy bound instance methods.  (Implemented by

  1237. Robert Collins; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1515">bpo-1515</a>.)</p></li>

  1238. <li><p>The <a class="reference internal" href="../library/ctypes.html#module-ctypes" title="ctypes: A foreign function library for Python."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ctypes</span></code></a> module now always converts <code class="docutils literal notranslate"><span class="pre">None</span></code> to a C <code class="docutils literal notranslate"><span class="pre">NULL</span></code>

  1239. pointer for arguments declared as pointers.  (Changed by Thomas

  1240. Heller; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4606">bpo-4606</a>.)  The underlying <a class="reference external" href="https://sourceware.org/libffi/">libffi library</a> has been updated to version

  1241. 3.0.9, containing various fixes for different platforms.  (Updated

  1242. by Matthias Klose; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8142">bpo-8142</a>.)</p></li>

  1243. <li><p>New method: the <a class="reference internal" href="../library/datetime.html#module-datetime" title="datetime: Basic date and time types."><code class="xref py py-mod docutils literal notranslate"><span class="pre">datetime</span></code></a> module’s <a class="reference internal" href="../library/datetime.html#datetime.timedelta" title="datetime.timedelta"><code class="xref py py-class docutils literal notranslate"><span class="pre">timedelta</span></code></a> class

  1244. gained a <a class="reference internal" href="../library/datetime.html#datetime.timedelta.total_seconds" title="datetime.timedelta.total_seconds"><code class="xref py py-meth docutils literal notranslate"><span class="pre">total_seconds()</span></code></a> method that returns the

  1245. number of seconds in the duration.  (Contributed by Brian Quinlan; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5788">bpo-5788</a>.)</p></li>

  1246. <li><p>New method: the <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a> class gained a

  1247. <a class="reference internal" href="../library/decimal.html#decimal.Decimal.from_float" title="decimal.Decimal.from_float"><code class="xref py py-meth docutils literal notranslate"><span class="pre">from_float()</span></code></a> class method that performs an exact

  1248. conversion of a floating-point number to a <code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code>.

  1249. This exact conversion strives for the

  1250. closest decimal approximation to the floating-point representation’s value;

  1251. the resulting decimal value will therefore still include the inaccuracy,

  1252. if any.

  1253. For example, <code class="docutils literal notranslate"><span class="pre">Decimal.from_float(0.1)</span></code> returns

  1254. <code class="docutils literal notranslate"><span class="pre">Decimal('0.1000000000000000055511151231257827021181583404541015625')</span></code>.

  1255. (Implemented by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4796">bpo-4796</a>.)</p>

  1256. <p>Comparing instances of <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a> with floating-point

  1257. numbers now produces sensible results based on the numeric values

  1258. of the operands.  Previously such comparisons would fall back to

  1259. Python’s default rules for comparing objects, which produced arbitrary

  1260. results based on their type.  Note that you still cannot combine

  1261. <code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code> and floating-point in other operations such as addition,

  1262. since you should be explicitly choosing how to convert between float and

  1263. <code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code>.  (Fixed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2531">bpo-2531</a>.)</p>

  1264. <p>The constructor for <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a> now accepts

  1265. floating-point numbers (added by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8257">bpo-8257</a>)

  1266. and non-European Unicode characters such as Arabic-Indic digits

  1267. (contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6595">bpo-6595</a>).</p>

  1268. <p>Most of the methods of the <a class="reference internal" href="../library/decimal.html#decimal.Context" title="decimal.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">Context</span></code></a> class now accept integers

  1269. as well as <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a> instances; the only exceptions are the

  1270. <a class="reference internal" href="../library/decimal.html#decimal.Context.canonical" title="decimal.Context.canonical"><code class="xref py py-meth docutils literal notranslate"><span class="pre">canonical()</span></code></a> and <a class="reference internal" href="../library/decimal.html#decimal.Context.is_canonical" title="decimal.Context.is_canonical"><code class="xref py py-meth docutils literal notranslate"><span class="pre">is_canonical()</span></code></a>

  1271. methods.  (Patch by Juan José Conti; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7633">bpo-7633</a>.)</p>

  1272. <p>When using <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a> instances with a string’s

  1273. <a class="reference internal" href="../library/stdtypes.html#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">format()</span></code></a> method, the default alignment was previously

  1274. left-alignment.  This has been changed to right-alignment, which is

  1275. more sensible for numeric types.  (Changed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6857">bpo-6857</a>.)</p>

  1276. <p>Comparisons involving a signaling NaN value (or <code class="docutils literal notranslate"><span class="pre">sNAN</span></code>) now signal

  1277. <a class="reference internal" href="../library/decimal.html#decimal.InvalidOperation" title="decimal.InvalidOperation"><code class="xref py py-const docutils literal notranslate"><span class="pre">InvalidOperation</span></code></a> instead of silently returning a true or

  1278. false value depending on the comparison operator.  Quiet NaN values

  1279. (or <code class="docutils literal notranslate"><span class="pre">NaN</span></code>) are now hashable.  (Fixed by Mark Dickinson;

  1280. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7279">bpo-7279</a>.)</p>

  1281. </li>

  1282. <li><p>The <a class="reference internal" href="../library/difflib.html#module-difflib" title="difflib: Helpers for computing differences between objects."><code class="xref py py-mod docutils literal notranslate"><span class="pre">difflib</span></code></a> module now produces output that is more

  1283. compatible with modern <strong class="command">diff</strong>/<strong class="command">patch</strong> tools

  1284. through one small change, using a tab character instead of spaces as

  1285. a separator in the header giving the filename.  (Fixed by Anatoly

  1286. Techtonik; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7585">bpo-7585</a>.)</p></li>

  1287. <li><p>The Distutils <code class="docutils literal notranslate"><span class="pre">sdist</span></code> command now always regenerates the

  1288. <code class="file docutils literal notranslate"><span class="pre">MANIFEST</span></code> file, since even if the <code class="file docutils literal notranslate"><span class="pre">MANIFEST.in</span></code> or

  1289. <code class="file docutils literal notranslate"><span class="pre">setup.py</span></code> files haven’t been modified, the user might have

  1290. created some new files that should be included.

  1291. (Fixed by Tarek Ziadé; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8688">bpo-8688</a>.)</p></li>

  1292. <li><p>The <a class="reference internal" href="../library/doctest.html#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate"><span class="pre">doctest</span></code></a> module’s <a class="reference internal" href="../library/doctest.html#doctest.IGNORE_EXCEPTION_DETAIL" title="doctest.IGNORE_EXCEPTION_DETAIL"><code class="xref py py-const docutils literal notranslate"><span class="pre">IGNORE_EXCEPTION_DETAIL</span></code></a> flag

  1293. will now ignore the name of the module containing the exception

  1294. being tested.  (Patch by Lennart Regebro; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7490">bpo-7490</a>.)</p></li>

  1295. <li><p>The <a class="reference internal" href="../library/email.html#module-email" title="email: Package supporting the parsing, manipulating, and generating email messages."><code class="xref py py-mod docutils literal notranslate"><span class="pre">email</span></code></a> module’s <a class="reference internal" href="../library/email.compat32-message.html#email.message.Message" title="email.message.Message"><code class="xref py py-class docutils literal notranslate"><span class="pre">Message</span></code></a> class will

  1296. now accept a Unicode-valued payload, automatically converting the

  1297. payload to the encoding specified by <code class="xref py py-attr docutils literal notranslate"><span class="pre">output_charset</span></code>.

  1298. (Added by R. David Murray; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1368247">bpo-1368247</a>.)</p></li>

  1299. <li><p>The <a class="reference internal" href="../library/fractions.html#fractions.Fraction" title="fractions.Fraction"><code class="xref py py-class docutils literal notranslate"><span class="pre">Fraction</span></code></a> class now accepts a single float or

  1300. <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a> instance, or two rational numbers, as

  1301. arguments to its constructor.  (Implemented by Mark Dickinson;

  1302. rationals added in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5812">bpo-5812</a>, and float/decimal in

  1303. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8294">bpo-8294</a>.)</p>

  1304. <p>Ordering comparisons (<code class="docutils literal notranslate"><span class="pre">&lt;</span></code>, <code class="docutils literal notranslate"><span class="pre">&lt;=</span></code>, <code class="docutils literal notranslate"><span class="pre">&gt;</span></code>, <code class="docutils literal notranslate"><span class="pre">&gt;=</span></code>) between

  1305. fractions and complex numbers now raise a <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>.

  1306. This fixes an oversight, making the <a class="reference internal" href="../library/fractions.html#fractions.Fraction" title="fractions.Fraction"><code class="xref py py-class docutils literal notranslate"><span class="pre">Fraction</span></code></a>

  1307. match the other numeric types.</p>

  1308. </li>

  1309. <li><p>New class: <a class="reference internal" href="../library/ftplib.html#ftplib.FTP_TLS" title="ftplib.FTP_TLS"><code class="xref py py-class docutils literal notranslate"><span class="pre">FTP_TLS</span></code></a> in

  1310. the <a class="reference internal" href="../library/ftplib.html#module-ftplib" title="ftplib: FTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ftplib</span></code></a> module provides secure FTP

  1311. connections using TLS encapsulation of authentication as well as

  1312. subsequent control and data transfers.

  1313. (Contributed by Giampaolo Rodola; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2054">bpo-2054</a>.)</p>

  1314. <p>The <a class="reference internal" href="../library/ftplib.html#ftplib.FTP.storbinary" title="ftplib.FTP.storbinary"><code class="xref py py-meth docutils literal notranslate"><span class="pre">storbinary()</span></code></a> method for binary uploads can now restart

  1315. uploads thanks to an added <em>rest</em> parameter (patch by Pablo Mouzo;

  1316. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6845">bpo-6845</a>.)</p>

  1317. </li>

  1318. <li><p>New class decorator: <a class="reference internal" href="../library/functools.html#functools.total_ordering" title="functools.total_ordering"><code class="xref py py-func docutils literal notranslate"><span class="pre">total_ordering()</span></code></a> in the <a class="reference internal" href="../library/functools.html#module-functools" title="functools: Higher-order functions and operations on callable objects."><code class="xref py py-mod docutils literal notranslate"><span class="pre">functools</span></code></a>

  1319. module takes a class that defines an <a class="reference internal" href="../reference/datamodel.html#object.__eq__" title="object.__eq__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__eq__()</span></code></a> method and one of

  1320. <a class="reference internal" href="../reference/datamodel.html#object.__lt__" title="object.__lt__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__lt__()</span></code></a>, <a class="reference internal" href="../reference/datamodel.html#object.__le__" title="object.__le__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__le__()</span></code></a>, <a class="reference internal" href="../reference/datamodel.html#object.__gt__" title="object.__gt__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__gt__()</span></code></a>, or <a class="reference internal" href="../reference/datamodel.html#object.__ge__" title="object.__ge__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__ge__()</span></code></a>,

  1321. and generates the missing comparison methods.  Since the

  1322. <code class="xref py py-meth docutils literal notranslate"><span class="pre">__cmp__()</span></code> method is being deprecated in Python 3.x,

  1323. this decorator makes it easier to define ordered classes.

  1324. (Added by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5479">bpo-5479</a>.)</p>

  1325. <p>New function: <a class="reference internal" href="../library/functools.html#functools.cmp_to_key" title="functools.cmp_to_key"><code class="xref py py-func docutils literal notranslate"><span class="pre">cmp_to_key()</span></code></a> will take an old-style comparison

  1326. function that expects two arguments and return a new callable that

  1327. can be used as the <em>key</em> parameter to functions such as

  1328. <a class="reference internal" href="../library/functions.html#sorted" title="sorted"><code class="xref py py-func docutils literal notranslate"><span class="pre">sorted()</span></code></a>, <a class="reference internal" href="../library/functions.html#min" title="min"><code class="xref py py-func docutils literal notranslate"><span class="pre">min()</span></code></a> and <a class="reference internal" href="../library/functions.html#max" title="max"><code class="xref py py-func docutils literal notranslate"><span class="pre">max()</span></code></a>, etc.  The primary

  1329. intended use is to help with making code compatible with Python 3.x.

  1330. (Added by Raymond Hettinger.)</p>

  1331. </li>

  1332. <li><p>New function: the <a class="reference internal" href="../library/gc.html#module-gc" title="gc: Interface to the cycle-detecting garbage collector."><code class="xref py py-mod docutils literal notranslate"><span class="pre">gc</span></code></a> module’s <a class="reference internal" href="../library/gc.html#gc.is_tracked" title="gc.is_tracked"><code class="xref py py-func docutils literal notranslate"><span class="pre">is_tracked()</span></code></a> returns

  1333. true if a given instance is tracked by the garbage collector, false

  1334. otherwise. (Contributed by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4688">bpo-4688</a>.)</p></li>

  1335. <li><p>The <a class="reference internal" href="../library/gzip.html#module-gzip" title="gzip: Interfaces for gzip compression and decompression using file objects."><code class="xref py py-mod docutils literal notranslate"><span class="pre">gzip</span></code></a> module’s <a class="reference internal" href="../library/gzip.html#gzip.GzipFile" title="gzip.GzipFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">GzipFile</span></code></a> now supports the context

  1336. management protocol, so you can write <code class="docutils literal notranslate"><span class="pre">with</span> <span class="pre">gzip.GzipFile(...)</span> <span class="pre">as</span> <span class="pre">f:</span></code>

  1337. (contributed by Hagen Fürstenau; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3860">bpo-3860</a>), and it now implements

  1338. the <a class="reference internal" href="../library/io.html#io.BufferedIOBase" title="io.BufferedIOBase"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.BufferedIOBase</span></code></a> ABC, so you can wrap it with

  1339. <a class="reference internal" href="../library/io.html#io.BufferedReader" title="io.BufferedReader"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.BufferedReader</span></code></a> for faster processing

  1340. (contributed by Nir Aides; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7471">bpo-7471</a>).

  1341. It’s also now possible to override the modification time

  1342. recorded in a gzipped file by providing an optional timestamp to

  1343. the constructor.  (Contributed by Jacques Frechet; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4272">bpo-4272</a>.)</p>

  1344. <p>Files in gzip format can be padded with trailing zero bytes; the

  1345. <a class="reference internal" href="../library/gzip.html#module-gzip" title="gzip: Interfaces for gzip compression and decompression using file objects."><code class="xref py py-mod docutils literal notranslate"><span class="pre">gzip</span></code></a> module will now consume these trailing bytes.  (Fixed by

  1346. Tadek Pietraszek and Brian Curtin; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2846">bpo-2846</a>.)</p>

  1347. </li>

  1348. <li><p>New attribute: the <a class="reference internal" href="../library/hashlib.html#module-hashlib" title="hashlib: Secure hash and message digest algorithms."><code class="xref py py-mod docutils literal notranslate"><span class="pre">hashlib</span></code></a> module now has an <code class="xref py py-attr docutils literal notranslate"><span class="pre">algorithms</span></code>

  1349. attribute containing a tuple naming the supported algorithms.

  1350. In Python 2.7, <code class="docutils literal notranslate"><span class="pre">hashlib.algorithms</span></code> contains

  1351. <code class="docutils literal notranslate"><span class="pre">('md5',</span> <span class="pre">'sha1',</span> <span class="pre">'sha224',</span> <span class="pre">'sha256',</span> <span class="pre">'sha384',</span> <span class="pre">'sha512')</span></code>.

  1352. (Contributed by Carl Chenet; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7418">bpo-7418</a>.)</p></li>

  1353. <li><p>The default <a class="reference internal" href="../library/http.client.html#http.client.HTTPResponse" title="http.client.HTTPResponse"><code class="xref py py-class docutils literal notranslate"><span class="pre">HTTPResponse</span></code></a> class used by the <a class="reference internal" href="../library/http.html#module-http" title="http: HTTP status codes and messages"><code class="xref py py-mod docutils literal notranslate"><span class="pre">httplib</span></code></a> module now

  1354. supports buffering, resulting in much faster reading of HTTP responses.

  1355. (Contributed by Kristján Valur Jónsson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4879">bpo-4879</a>.)</p>

  1356. <p>The <a class="reference internal" href="../library/http.client.html#http.client.HTTPConnection" title="http.client.HTTPConnection"><code class="xref py py-class docutils literal notranslate"><span class="pre">HTTPConnection</span></code></a> and <a class="reference internal" href="../library/http.client.html#http.client.HTTPSConnection" title="http.client.HTTPSConnection"><code class="xref py py-class docutils literal notranslate"><span class="pre">HTTPSConnection</span></code></a> classes

  1357. now support a <em>source_address</em> parameter, a <code class="docutils literal notranslate"><span class="pre">(host,</span> <span class="pre">port)</span></code> 2-tuple

  1358. giving the source address that will be used for the connection.

  1359. (Contributed by Eldon Ziegler; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3972">bpo-3972</a>.)</p>

  1360. </li>

  1361. <li><p>The <code class="xref py py-mod docutils literal notranslate"><span class="pre">ihooks</span></code> module now supports relative imports.  Note that

  1362. <code class="xref py py-mod docutils literal notranslate"><span class="pre">ihooks</span></code> is an older module for customizing imports,

  1363. superseded by the <code class="xref py py-mod docutils literal notranslate"><span class="pre">imputil</span></code> module added in Python 2.0.

  1364. (Relative import support added by Neil Schemenauer.)</p>

  1365. </li>

  1366. <li><p>The <a class="reference internal" href="../library/imaplib.html#module-imaplib" title="imaplib: IMAP4 protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">imaplib</span></code></a> module now supports IPv6 addresses.

  1367. (Contributed by Derek Morr; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1655">bpo-1655</a>.)</p></li>

  1368. <li><p>New function: the <a class="reference internal" href="../library/inspect.html#module-inspect" title="inspect: Extract information and source code from live objects."><code class="xref py py-mod docutils literal notranslate"><span class="pre">inspect</span></code></a> module’s <a class="reference internal" href="../library/inspect.html#inspect.getcallargs" title="inspect.getcallargs"><code class="xref py py-func docutils literal notranslate"><span class="pre">getcallargs()</span></code></a>

  1369. takes a callable and its positional and keyword arguments,

  1370. and figures out which of the callable’s parameters will receive each argument,

  1371. returning a dictionary mapping argument names to their values.  For example:</p>

  1372. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">inspect</span> <span class="kn">import</span> <span class="n">getcallargs</span>

  1373. <span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">f</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="n">b</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="o">*</span><span class="n">pos</span><span class="p">,</span> <span class="o">**</span><span class="n">named</span><span class="p">):</span>

  1374. <span class="gp">... </span>    <span class="k">pass</span>

  1375. <span class="gp">...</span>

  1376. <span class="gp">&gt;&gt;&gt; </span><span class="n">getcallargs</span><span class="p">(</span><span class="n">f</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">)</span>

  1377. <span class="go">{&#39;a&#39;: 1, &#39;b&#39;: 2, &#39;pos&#39;: (3,), &#39;named&#39;: {}}</span>

  1378. <span class="gp">&gt;&gt;&gt; </span><span class="n">getcallargs</span><span class="p">(</span><span class="n">f</span><span class="p">,</span> <span class="n">a</span><span class="o">=</span><span class="mi">2</span><span class="p">,</span> <span class="n">x</span><span class="o">=</span><span class="mi">4</span><span class="p">)</span>

  1379. <span class="go">{&#39;a&#39;: 2, &#39;b&#39;: 1, &#39;pos&#39;: (), &#39;named&#39;: {&#39;x&#39;: 4}}</span>

  1380. <span class="gp">&gt;&gt;&gt; </span><span class="n">getcallargs</span><span class="p">(</span><span class="n">f</span><span class="p">)</span>

  1381. <span class="gt">Traceback (most recent call last):</span>

  1382. <span class="c">...</span>

  1383. <span class="gr">TypeError</span>: <span class="n">f() takes at least 1 argument (0 given)</span>

  1384. </pre></div>

  1385. </div>

  1386. <p>Contributed by George Sakkis; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3135">bpo-3135</a>.</p>

  1387. </li>

  1388. <li><p>Updated module: The <a class="reference internal" href="../library/io.html#module-io" title="io: Core tools for working with streams."><code class="xref py py-mod docutils literal notranslate"><span class="pre">io</span></code></a> library has been upgraded to the version shipped with

  1389. Python 3.1.  For 3.1, the I/O library was entirely rewritten in C

  1390. and is 2 to 20 times faster depending on the task being performed.  The

  1391. original Python version was renamed to the <code class="xref py py-mod docutils literal notranslate"><span class="pre">_pyio</span></code> module.</p>

  1392. <p>One minor resulting change: the <a class="reference internal" href="../library/io.html#io.TextIOBase" title="io.TextIOBase"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.TextIOBase</span></code></a> class now

  1393. has an <a class="reference internal" href="../library/io.html#io.TextIOBase.errors" title="io.TextIOBase.errors"><code class="xref py py-attr docutils literal notranslate"><span class="pre">errors</span></code></a> attribute giving the error setting

  1394. used for encoding and decoding errors (one of <code class="docutils literal notranslate"><span class="pre">'strict'</span></code>, <code class="docutils literal notranslate"><span class="pre">'replace'</span></code>,

  1395. <code class="docutils literal notranslate"><span class="pre">'ignore'</span></code>).</p>

  1396. <p>The <a class="reference internal" href="../library/io.html#io.FileIO" title="io.FileIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.FileIO</span></code></a> class now raises an <a class="reference internal" href="../library/exceptions.html#OSError" title="OSError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OSError</span></code></a> when passed

  1397. an invalid file descriptor.  (Implemented by Benjamin Peterson;

  1398. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4991">bpo-4991</a>.)  The <a class="reference internal" href="../library/io.html#io.IOBase.truncate" title="io.IOBase.truncate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">truncate()</span></code></a> method now preserves the

  1399. file position; previously it would change the file position to the

  1400. end of the new file.  (Fixed by Pascal Chambon; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6939">bpo-6939</a>.)</p>

  1401. </li>

  1402. <li><p>New function: <code class="docutils literal notranslate"><span class="pre">itertools.compress(data,</span> <span class="pre">selectors)</span></code> takes two

  1403. iterators.  Elements of <em>data</em> are returned if the corresponding

  1404. value in <em>selectors</em> is true:</p>

  1405. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">itertools</span><span class="o">.</span><span class="n">compress</span><span class="p">(</span><span class="s1">&#39;ABCDEF&#39;</span><span class="p">,</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">1</span><span class="p">])</span> <span class="o">=&gt;</span>

  1406.   <span class="n">A</span><span class="p">,</span> <span class="n">C</span><span class="p">,</span> <span class="n">E</span><span class="p">,</span> <span class="n">F</span>

  1407. </pre></div>

  1408. </div>

  1409. <p>New function: <code class="docutils literal notranslate"><span class="pre">itertools.combinations_with_replacement(iter,</span> <span class="pre">r)</span></code>

  1410. returns all the possible <em>r</em>-length combinations of elements from the

  1411. iterable <em>iter</em>.  Unlike <a class="reference internal" href="../library/itertools.html#itertools.combinations" title="itertools.combinations"><code class="xref py py-func docutils literal notranslate"><span class="pre">combinations()</span></code></a>, individual elements

  1412. can be repeated in the generated combinations:</p>

  1413. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">itertools</span><span class="o">.</span><span class="n">combinations_with_replacement</span><span class="p">(</span><span class="s1">&#39;abc&#39;</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span> <span class="o">=&gt;</span>

  1414.   <span class="p">(</span><span class="s1">&#39;a&#39;</span><span class="p">,</span> <span class="s1">&#39;a&#39;</span><span class="p">),</span> <span class="p">(</span><span class="s1">&#39;a&#39;</span><span class="p">,</span> <span class="s1">&#39;b&#39;</span><span class="p">),</span> <span class="p">(</span><span class="s1">&#39;a&#39;</span><span class="p">,</span> <span class="s1">&#39;c&#39;</span><span class="p">),</span>

  1415.   <span class="p">(</span><span class="s1">&#39;b&#39;</span><span class="p">,</span> <span class="s1">&#39;b&#39;</span><span class="p">),</span> <span class="p">(</span><span class="s1">&#39;b&#39;</span><span class="p">,</span> <span class="s1">&#39;c&#39;</span><span class="p">),</span> <span class="p">(</span><span class="s1">&#39;c&#39;</span><span class="p">,</span> <span class="s1">&#39;c&#39;</span><span class="p">)</span>

  1416. </pre></div>

  1417. </div>

  1418. <p>Note that elements are treated as unique depending on their position

  1419. in the input, not their actual values.</p>

  1420. <p>The <a class="reference internal" href="../library/itertools.html#itertools.count" title="itertools.count"><code class="xref py py-func docutils literal notranslate"><span class="pre">itertools.count()</span></code></a> function now has a <em>step</em> argument that

  1421. allows incrementing by values other than 1.  <a class="reference internal" href="../library/itertools.html#itertools.count" title="itertools.count"><code class="xref py py-func docutils literal notranslate"><span class="pre">count()</span></code></a> also

  1422. now allows keyword arguments, and using non-integer values such as

  1423. floats or <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a> instances.  (Implemented by Raymond

  1424. Hettinger; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5032">bpo-5032</a>.)</p>

  1425. <p><a class="reference internal" href="../library/itertools.html#itertools.combinations" title="itertools.combinations"><code class="xref py py-func docutils literal notranslate"><span class="pre">itertools.combinations()</span></code></a> and <a class="reference internal" href="../library/itertools.html#itertools.product" title="itertools.product"><code class="xref py py-func docutils literal notranslate"><span class="pre">itertools.product()</span></code></a>

  1426. previously raised <a class="reference internal" href="../library/exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> for values of <em>r</em> larger than

  1427. the input iterable.  This was deemed a specification error, so they

  1428. now return an empty iterator.  (Fixed by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4816">bpo-4816</a>.)</p>

  1429. </li>

  1430. <li><p>Updated module: The <a class="reference internal" href="../library/json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json</span></code></a> module was upgraded to version 2.0.9 of the

  1431. simplejson package, which includes a C extension that makes

  1432. encoding and decoding faster.

  1433. (Contributed by Bob Ippolito; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4136">bpo-4136</a>.)</p>

  1434. <p>To support the new <a class="reference internal" href="../library/collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.OrderedDict</span></code></a> type, <a class="reference internal" href="../library/json.html#json.load" title="json.load"><code class="xref py py-func docutils literal notranslate"><span class="pre">json.load()</span></code></a>

  1435. now has an optional <em>object_pairs_hook</em> parameter that will be called

  1436. with any object literal that decodes to a list of pairs.

  1437. (Contributed by Raymond Hettinger; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5381">bpo-5381</a>.)</p>

  1438. </li>

  1439. <li><p>The <a class="reference internal" href="../library/mailbox.html#module-mailbox" title="mailbox: Manipulate mailboxes in various formats"><code class="xref py py-mod docutils literal notranslate"><span class="pre">mailbox</span></code></a> module’s <a class="reference internal" href="../library/mailbox.html#mailbox.Maildir" title="mailbox.Maildir"><code class="xref py py-class docutils literal notranslate"><span class="pre">Maildir</span></code></a> class now records the

  1440. timestamp on the directories it reads, and only re-reads them if the

  1441. modification time has subsequently changed.  This improves

  1442. performance by avoiding unneeded directory scans.  (Fixed by

  1443. A.M. Kuchling and Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1607951">bpo-1607951</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6896">bpo-6896</a>.)</p></li>

  1444. <li><p>New functions: the <a class="reference internal" href="../library/math.html#module-math" title="math: Mathematical functions (sin() etc.)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">math</span></code></a> module gained

  1445. <a class="reference internal" href="../library/math.html#math.erf" title="math.erf"><code class="xref py py-func docutils literal notranslate"><span class="pre">erf()</span></code></a> and <a class="reference internal" href="../library/math.html#math.erfc" title="math.erfc"><code class="xref py py-func docutils literal notranslate"><span class="pre">erfc()</span></code></a> for the error function and the complementary error function,

  1446. <a class="reference internal" href="../library/math.html#math.expm1" title="math.expm1"><code class="xref py py-func docutils literal notranslate"><span class="pre">expm1()</span></code></a> which computes <code class="docutils literal notranslate"><span class="pre">e**x</span> <span class="pre">-</span> <span class="pre">1</span></code> with more precision than

  1447. using <a class="reference internal" href="../library/math.html#math.exp" title="math.exp"><code class="xref py py-func docutils literal notranslate"><span class="pre">exp()</span></code></a> and subtracting 1,

  1448. <a class="reference internal" href="../library/math.html#math.gamma" title="math.gamma"><code class="xref py py-func docutils literal notranslate"><span class="pre">gamma()</span></code></a> for the Gamma function, and

  1449. <a class="reference internal" href="../library/math.html#math.lgamma" title="math.lgamma"><code class="xref py py-func docutils literal notranslate"><span class="pre">lgamma()</span></code></a> for the natural log of the Gamma function.

  1450. (Contributed by Mark Dickinson and nirinA raseliarison; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3366">bpo-3366</a>.)</p></li>

  1451. <li><p>The <a class="reference internal" href="../library/multiprocessing.html#module-multiprocessing" title="multiprocessing: Process-based parallelism."><code class="xref py py-mod docutils literal notranslate"><span class="pre">multiprocessing</span></code></a> module’s <code class="xref py py-class docutils literal notranslate"><span class="pre">Manager*</span></code> classes

  1452. can now be passed a callable that will be called whenever

  1453. a subprocess is started, along with a set of arguments that will be

  1454. passed to the callable.

  1455. (Contributed by lekma; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5585">bpo-5585</a>.)</p>

  1456. <p>The <a class="reference internal" href="../library/multiprocessing.html#multiprocessing.pool.Pool" title="multiprocessing.pool.Pool"><code class="xref py py-class docutils literal notranslate"><span class="pre">Pool</span></code></a> class, which controls a pool of worker processes,

  1457. now has an optional <em>maxtasksperchild</em> parameter.  Worker processes

  1458. will perform the specified number of tasks and then exit, causing the

  1459. <code class="xref py py-class docutils literal notranslate"><span class="pre">Pool</span></code> to start a new worker.  This is useful if tasks may leak

  1460. memory or other resources, or if some tasks will cause the worker to

  1461. become very large.

  1462. (Contributed by Charles Cazabon; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6963">bpo-6963</a>.)</p>

  1463. </li>

  1464. <li><p>The <a class="reference internal" href="../library/nntplib.html#module-nntplib" title="nntplib: NNTP protocol client (requires sockets). (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">nntplib</span></code></a> module now supports IPv6 addresses.

  1465. (Contributed by Derek Morr; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1664">bpo-1664</a>.)</p></li>

  1466. <li><p>New functions: the <a class="reference internal" href="../library/os.html#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal notranslate"><span class="pre">os</span></code></a> module wraps the following POSIX system

  1467. calls: <a class="reference internal" href="../library/os.html#os.getresgid" title="os.getresgid"><code class="xref py py-func docutils literal notranslate"><span class="pre">getresgid()</span></code></a> and <a class="reference internal" href="../library/os.html#os.getresuid" title="os.getresuid"><code class="xref py py-func docutils literal notranslate"><span class="pre">getresuid()</span></code></a>, which return the

  1468. real, effective, and saved GIDs and UIDs;

  1469. <a class="reference internal" href="../library/os.html#os.setresgid" title="os.setresgid"><code class="xref py py-func docutils literal notranslate"><span class="pre">setresgid()</span></code></a> and <a class="reference internal" href="../library/os.html#os.setresuid" title="os.setresuid"><code class="xref py py-func docutils literal notranslate"><span class="pre">setresuid()</span></code></a>, which set

  1470. real, effective, and saved GIDs and UIDs to new values;

  1471. <a class="reference internal" href="../library/os.html#os.initgroups" title="os.initgroups"><code class="xref py py-func docutils literal notranslate"><span class="pre">initgroups()</span></code></a>, which initialize the group access list

  1472. for the current process.  (GID/UID functions

  1473. contributed by Travis H.; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6508">bpo-6508</a>.  Support for initgroups added

  1474. by Jean-Paul Calderone; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7333">bpo-7333</a>.)</p>

  1475. <p>The <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fork()</span></code></a> function now re-initializes the import lock in

  1476. the child process; this fixes problems on Solaris when <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">fork()</span></code></a>

  1477. is called from a thread.  (Fixed by Zsolt Cserna; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7242">bpo-7242</a>.)</p>

  1478. </li>

  1479. <li><p>In the <a class="reference internal" href="../library/os.path.html#module-os.path" title="os.path: Operations on pathnames."><code class="xref py py-mod docutils literal notranslate"><span class="pre">os.path</span></code></a> module, the <a class="reference internal" href="../library/os.path.html#os.path.normpath" title="os.path.normpath"><code class="xref py py-func docutils literal notranslate"><span class="pre">normpath()</span></code></a> and

  1480. <a class="reference internal" href="../library/os.path.html#os.path.abspath" title="os.path.abspath"><code class="xref py py-func docutils literal notranslate"><span class="pre">abspath()</span></code></a> functions now preserve Unicode; if their input path

  1481. is a Unicode string, the return value is also a Unicode string.

  1482. (<a class="reference internal" href="../library/os.path.html#os.path.normpath" title="os.path.normpath"><code class="xref py py-meth docutils literal notranslate"><span class="pre">normpath()</span></code></a> fixed by Matt Giuca in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5827">bpo-5827</a>;

  1483. <a class="reference internal" href="../library/os.path.html#os.path.abspath" title="os.path.abspath"><code class="xref py py-meth docutils literal notranslate"><span class="pre">abspath()</span></code></a> fixed by Ezio Melotti in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3426">bpo-3426</a>.)</p></li>

  1484. <li><p>The <a class="reference internal" href="../library/pydoc.html#module-pydoc" title="pydoc: Documentation generator and online help system."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pydoc</span></code></a> module now has help for the various symbols that Python

  1485. uses.  You can now do <code class="docutils literal notranslate"><span class="pre">help('&lt;&lt;')</span></code> or <code class="docutils literal notranslate"><span class="pre">help('&#64;')</span></code>, for example.

  1486. (Contributed by David Laban; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4739">bpo-4739</a>.)</p></li>

  1487. <li><p>The <a class="reference internal" href="../library/re.html#module-re" title="re: Regular expression operations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">re</span></code></a> module’s <a class="reference internal" href="../library/re.html#re.split" title="re.split"><code class="xref py py-func docutils literal notranslate"><span class="pre">split()</span></code></a>, <a class="reference internal" href="../library/re.html#re.sub" title="re.sub"><code class="xref py py-func docutils literal notranslate"><span class="pre">sub()</span></code></a>, and <a class="reference internal" href="../library/re.html#re.subn" title="re.subn"><code class="xref py py-func docutils literal notranslate"><span class="pre">subn()</span></code></a>

  1488. now accept an optional <em>flags</em> argument, for consistency with the

  1489. other functions in the module.  (Added by Gregory P. Smith.)</p></li>

  1490. <li><p>New function: <a class="reference internal" href="../library/runpy.html#runpy.run_path" title="runpy.run_path"><code class="xref py py-func docutils literal notranslate"><span class="pre">run_path()</span></code></a> in the <a class="reference internal" href="../library/runpy.html#module-runpy" title="runpy: Locate and run Python modules without importing them first."><code class="xref py py-mod docutils literal notranslate"><span class="pre">runpy</span></code></a> module

  1491. will execute the code at a provided <em>path</em> argument.  <em>path</em> can be

  1492. the path of a Python source file (<code class="file docutils literal notranslate"><span class="pre">example.py</span></code>), a compiled

  1493. bytecode file (<code class="file docutils literal notranslate"><span class="pre">example.pyc</span></code>), a directory

  1494. (<code class="file docutils literal notranslate"><span class="pre">./package/</span></code>), or a zip archive (<code class="file docutils literal notranslate"><span class="pre">example.zip</span></code>).  If a

  1495. directory or zip path is provided, it will be added to the front of

  1496. <code class="docutils literal notranslate"><span class="pre">sys.path</span></code> and the module <a class="reference internal" href="../library/__main__.html#module-__main__" title="__main__: The environment where top-level code is run. Covers command-line interfaces, import-time behavior, and ``__name__ == '__main__'``."><code class="xref py py-mod docutils literal notranslate"><span class="pre">__main__</span></code></a> will be imported.  It’s

  1497. expected that the directory or zip contains a <code class="file docutils literal notranslate"><span class="pre">__main__.py</span></code>;

  1498. if it doesn’t, some other <code class="file docutils literal notranslate"><span class="pre">__main__.py</span></code> might be imported from

  1499. a location later in <code class="docutils literal notranslate"><span class="pre">sys.path</span></code>.  This makes more of the machinery

  1500. of <a class="reference internal" href="../library/runpy.html#module-runpy" title="runpy: Locate and run Python modules without importing them first."><code class="xref py py-mod docutils literal notranslate"><span class="pre">runpy</span></code></a> available to scripts that want to mimic the way

  1501. Python’s command line processes an explicit path name.

  1502. (Added by Nick Coghlan; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6816">bpo-6816</a>.)</p></li>

  1503. <li><p>New function: in the <a class="reference internal" href="../library/shutil.html#module-shutil" title="shutil: High-level file operations, including copying."><code class="xref py py-mod docutils literal notranslate"><span class="pre">shutil</span></code></a> module, <a class="reference internal" href="../library/shutil.html#shutil.make_archive" title="shutil.make_archive"><code class="xref py py-func docutils literal notranslate"><span class="pre">make_archive()</span></code></a>

  1504. takes a filename, archive type (zip or tar-format), and a directory

  1505. path, and creates an archive containing the directory’s contents.

  1506. (Added by Tarek Ziadé.)</p>

  1507. <p><a class="reference internal" href="../library/shutil.html#module-shutil" title="shutil: High-level file operations, including copying."><code class="xref py py-mod docutils literal notranslate"><span class="pre">shutil</span></code></a>’s <a class="reference internal" href="../library/shutil.html#shutil.copyfile" title="shutil.copyfile"><code class="xref py py-func docutils literal notranslate"><span class="pre">copyfile()</span></code></a> and <a class="reference internal" href="../library/shutil.html#shutil.copytree" title="shutil.copytree"><code class="xref py py-func docutils literal notranslate"><span class="pre">copytree()</span></code></a>

  1508. functions now raise a <code class="xref py py-exc docutils literal notranslate"><span class="pre">SpecialFileError</span></code> exception when

  1509. asked to copy a named pipe.  Previously the code would treat

  1510. named pipes like a regular file by opening them for reading, and

  1511. this would block indefinitely.  (Fixed by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3002">bpo-3002</a>.)</p>

  1512. </li>

  1513. <li><p>The <a class="reference internal" href="../library/signal.html#module-signal" title="signal: Set handlers for asynchronous events."><code class="xref py py-mod docutils literal notranslate"><span class="pre">signal</span></code></a> module no longer re-installs the signal handler

  1514. unless this is truly necessary, which fixes a bug that could make it

  1515. impossible to catch the EINTR signal robustly.  (Fixed by

  1516. Charles-Francois Natali; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8354">bpo-8354</a>.)</p></li>

  1517. <li><p>New functions: in the <a class="reference internal" href="../library/site.html#module-site" title="site: Module responsible for site-specific configuration."><code class="xref py py-mod docutils literal notranslate"><span class="pre">site</span></code></a> module, three new functions

  1518. return various site- and user-specific paths.

  1519. <a class="reference internal" href="../library/site.html#site.getsitepackages" title="site.getsitepackages"><code class="xref py py-func docutils literal notranslate"><span class="pre">getsitepackages()</span></code></a> returns a list containing all

  1520. global site-packages directories,

  1521. <a class="reference internal" href="../library/site.html#site.getusersitepackages" title="site.getusersitepackages"><code class="xref py py-func docutils literal notranslate"><span class="pre">getusersitepackages()</span></code></a> returns the path of the user’s

  1522. site-packages directory, and

  1523. <a class="reference internal" href="../library/site.html#site.getuserbase" title="site.getuserbase"><code class="xref py py-func docutils literal notranslate"><span class="pre">getuserbase()</span></code></a> returns the value of the <a class="reference internal" href="../library/site.html#site.USER_BASE" title="site.USER_BASE"><code class="xref py py-data docutils literal notranslate"><span class="pre">USER_BASE</span></code></a>

  1524. environment variable, giving the path to a directory that can be used

  1525. to store data.

  1526. (Contributed by Tarek Ziadé; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6693">bpo-6693</a>.)</p>

  1527. <p>The <a class="reference internal" href="../library/site.html#module-site" title="site: Module responsible for site-specific configuration."><code class="xref py py-mod docutils literal notranslate"><span class="pre">site</span></code></a> module now reports exceptions occurring

  1528. when the <a class="reference internal" href="../library/site.html#module-sitecustomize" title="sitecustomize"><code class="xref py py-mod docutils literal notranslate"><span class="pre">sitecustomize</span></code></a> module is imported, and will no longer

  1529. catch and swallow the <a class="reference internal" href="../library/exceptions.html#KeyboardInterrupt" title="KeyboardInterrupt"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyboardInterrupt</span></code></a> exception.  (Fixed by

  1530. Victor Stinner; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3137">bpo-3137</a>.)</p>

  1531. </li>

  1532. <li><p>The <a class="reference internal" href="../library/socket.html#socket.create_connection" title="socket.create_connection"><code class="xref py py-func docutils literal notranslate"><span class="pre">create_connection()</span></code></a> function

  1533. gained a <em>source_address</em> parameter, a <code class="docutils literal notranslate"><span class="pre">(host,</span> <span class="pre">port)</span></code> 2-tuple

  1534. giving the source address that will be used for the connection.

  1535. (Contributed by Eldon Ziegler; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3972">bpo-3972</a>.)</p>

  1536. <p>The <a class="reference internal" href="../library/socket.html#socket.socket.recv_into" title="socket.socket.recv_into"><code class="xref py py-meth docutils literal notranslate"><span class="pre">recv_into()</span></code></a> and <a class="reference internal" href="../library/socket.html#socket.socket.recvfrom_into" title="socket.socket.recvfrom_into"><code class="xref py py-meth docutils literal notranslate"><span class="pre">recvfrom_into()</span></code></a>

  1537. methods will now write into objects that support the buffer API, most usefully

  1538. the <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> and <a class="reference internal" href="../library/stdtypes.html#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> objects.  (Implemented by

  1539. Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8104">bpo-8104</a>.)</p>

  1540. </li>

  1541. <li><p>The <a class="reference internal" href="../library/socketserver.html#module-socketserver" title="socketserver: A framework for network servers."><code class="xref py py-mod docutils literal notranslate"><span class="pre">SocketServer</span></code></a> module’s <a class="reference internal" href="../library/socketserver.html#socketserver.TCPServer" title="socketserver.TCPServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">TCPServer</span></code></a> class now

  1542. supports socket timeouts and disabling the Nagle algorithm.

  1543. The <code class="xref py py-attr docutils literal notranslate"><span class="pre">disable_nagle_algorithm</span></code> class attribute

  1544. defaults to <code class="docutils literal notranslate"><span class="pre">False</span></code>; if overridden to be true,

  1545. new request connections will have the TCP_NODELAY option set to

  1546. prevent buffering many small sends into a single TCP packet.

  1547. The <a class="reference internal" href="../library/socketserver.html#socketserver.BaseServer.timeout" title="socketserver.BaseServer.timeout"><code class="xref py py-attr docutils literal notranslate"><span class="pre">timeout</span></code></a> class attribute can hold

  1548. a timeout in seconds that will be applied to the request socket; if

  1549. no request is received within that time, <a class="reference internal" href="../library/socketserver.html#socketserver.BaseServer.handle_timeout" title="socketserver.BaseServer.handle_timeout"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle_timeout()</span></code></a>

  1550. will be called and <a class="reference internal" href="../library/socketserver.html#socketserver.BaseServer.handle_request" title="socketserver.BaseServer.handle_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">handle_request()</span></code></a> will return.

  1551. (Contributed by Kristján Valur Jónsson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6192">bpo-6192</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6267">bpo-6267</a>.)</p></li>

  1552. <li><p>Updated module: the <a class="reference internal" href="../library/sqlite3.html#module-sqlite3" title="sqlite3: A DB-API 2.0 implementation using SQLite 3.x."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sqlite3</span></code></a> module has been updated to

  1553. version 2.6.0 of the <a class="reference external" href="https://github.com/ghaering/pysqlite">pysqlite package</a>. Version 2.6.0 includes a number of bugfixes, and adds

  1554. the ability to load SQLite extensions from shared libraries.

  1555. Call the <code class="docutils literal notranslate"><span class="pre">enable_load_extension(True)</span></code> method to enable extensions,

  1556. and then call <a class="reference internal" href="../library/sqlite3.html#sqlite3.Connection.load_extension" title="sqlite3.Connection.load_extension"><code class="xref py py-meth docutils literal notranslate"><span class="pre">load_extension()</span></code></a> to load a particular shared library.

  1557. (Updated by Gerhard Häring.)</p></li>

  1558. <li><p>The <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate"><span class="pre">ssl</span></code></a> module’s <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket" title="ssl.SSLSocket"><code class="xref py py-class docutils literal notranslate"><span class="pre">SSLSocket</span></code></a> objects now support the

  1559. buffer API, which fixed a test suite failure (fix by Antoine Pitrou;

  1560. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7133">bpo-7133</a>) and automatically set

  1561. OpenSSL’s <code class="xref c c-macro docutils literal notranslate"><span class="pre">SSL_MODE_AUTO_RETRY</span></code>, which will prevent an error

  1562. code being returned from <code class="xref py py-meth docutils literal notranslate"><span class="pre">recv()</span></code> operations that trigger an SSL

  1563. renegotiation (fix by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8222">bpo-8222</a>).</p>

  1564. <p>The <a class="reference internal" href="../library/ssl.html#ssl.SSLContext.wrap_socket" title="ssl.SSLContext.wrap_socket"><code class="xref py py-func docutils literal notranslate"><span class="pre">wrap_socket()</span></code></a> constructor function now takes a

  1565. <em>ciphers</em> argument that’s a string listing the encryption algorithms

  1566. to be allowed; the format of the string is described

  1567. <a class="reference external" href="https://www.openssl.org/docs/man1.0.2/man1/ciphers.html">in the OpenSSL documentation</a>.

  1568. (Added by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8322">bpo-8322</a>.)</p>

  1569. <p>Another change makes the extension load all of OpenSSL’s ciphers and

  1570. digest algorithms so that they’re all available.  Some SSL

  1571. certificates couldn’t be verified, reporting an “unknown algorithm”

  1572. error.  (Reported by Beda Kosata, and fixed by Antoine Pitrou;

  1573. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8484">bpo-8484</a>.)</p>

  1574. <p>The version of OpenSSL being used is now available as the module

  1575. attributes <a class="reference internal" href="../library/ssl.html#ssl.OPENSSL_VERSION" title="ssl.OPENSSL_VERSION"><code class="xref py py-const docutils literal notranslate"><span class="pre">ssl.OPENSSL_VERSION</span></code></a> (a string),

  1576. <a class="reference internal" href="../library/ssl.html#ssl.OPENSSL_VERSION_INFO" title="ssl.OPENSSL_VERSION_INFO"><code class="xref py py-const docutils literal notranslate"><span class="pre">ssl.OPENSSL_VERSION_INFO</span></code></a> (a 5-tuple), and

  1577. <a class="reference internal" href="../library/ssl.html#ssl.OPENSSL_VERSION_NUMBER" title="ssl.OPENSSL_VERSION_NUMBER"><code class="xref py py-const docutils literal notranslate"><span class="pre">ssl.OPENSSL_VERSION_NUMBER</span></code></a> (an integer).  (Added by Antoine

  1578. Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8321">bpo-8321</a>.)</p>

  1579. </li>

  1580. <li><p>The <a class="reference internal" href="../library/struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate"><span class="pre">struct</span></code></a> module will no longer silently ignore overflow

  1581. errors when a value is too large for a particular integer format

  1582. code (one of <code class="docutils literal notranslate"><span class="pre">bBhHiIlLqQ</span></code>); it now always raises a

  1583. <a class="reference internal" href="../library/struct.html#struct.error" title="struct.error"><code class="xref py py-exc docutils literal notranslate"><span class="pre">struct.error</span></code></a> exception.  (Changed by Mark Dickinson;

  1584. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1523">bpo-1523</a>.)  The <a class="reference internal" href="../library/struct.html#struct.pack" title="struct.pack"><code class="xref py py-func docutils literal notranslate"><span class="pre">pack()</span></code></a> function will also

  1585. attempt to use <a class="reference internal" href="../reference/datamodel.html#object.__index__" title="object.__index__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__index__()</span></code></a> to convert and pack non-integers

  1586. before trying the <a class="reference internal" href="../reference/datamodel.html#object.__int__" title="object.__int__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__int__()</span></code></a> method or reporting an error.

  1587. (Changed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8300">bpo-8300</a>.)</p></li>

  1588. <li><p>New function: the <a class="reference internal" href="../library/subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> module’s

  1589. <a class="reference internal" href="../library/subprocess.html#subprocess.check_output" title="subprocess.check_output"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_output()</span></code></a> runs a command with a specified set of arguments

  1590. and returns the command’s output as a string when the command runs without

  1591. error, or raises a <a class="reference internal" href="../library/subprocess.html#subprocess.CalledProcessError" title="subprocess.CalledProcessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CalledProcessError</span></code></a> exception otherwise.</p>

  1592. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">check_output</span><span class="p">([</span><span class="s1">&#39;df&#39;</span><span class="p">,</span> <span class="s1">&#39;-h&#39;</span><span class="p">,</span> <span class="s1">&#39;.&#39;</span><span class="p">])</span>

  1593. <span class="go">&#39;Filesystem     Size   Used  Avail Capacity  Mounted on\n</span>

  1594. <span class="go">/dev/disk0s2    52G    49G   3.0G    94%    /\n&#39;</span>

  1595. 

  1596. <span class="gp">&gt;&gt;&gt; </span><span class="n">subprocess</span><span class="o">.</span><span class="n">check_output</span><span class="p">([</span><span class="s1">&#39;df&#39;</span><span class="p">,</span> <span class="s1">&#39;-h&#39;</span><span class="p">,</span> <span class="s1">&#39;/bogus&#39;</span><span class="p">])</span>

  1597. <span class="go">  ...</span>

  1598. <span class="go">subprocess.CalledProcessError: Command &#39;[&#39;df&#39;, &#39;-h&#39;, &#39;/bogus&#39;]&#39; returned non-zero exit status 1</span>

  1599. </pre></div>

  1600. </div>

  1601. <p>(Contributed by Gregory P. Smith.)</p>

  1602. <p>The <a class="reference internal" href="../library/subprocess.html#module-subprocess" title="subprocess: Subprocess management."><code class="xref py py-mod docutils literal notranslate"><span class="pre">subprocess</span></code></a> module will now retry its internal system calls

  1603. on receiving an <a class="reference internal" href="../library/errno.html#errno.EINTR" title="errno.EINTR"><code class="xref py py-const docutils literal notranslate"><span class="pre">EINTR</span></code></a> signal.  (Reported by several people; final

  1604. patch by Gregory P. Smith in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1068268">bpo-1068268</a>.)</p>

  1605. </li>

  1606. <li><p>New function: <a class="reference internal" href="../library/symtable.html#symtable.Symbol.is_declared_global" title="symtable.Symbol.is_declared_global"><code class="xref py py-func docutils literal notranslate"><span class="pre">is_declared_global()</span></code></a> in the <a class="reference internal" href="../library/symtable.html#module-symtable" title="symtable: Interface to the compiler's internal symbol tables."><code class="xref py py-mod docutils literal notranslate"><span class="pre">symtable</span></code></a> module

  1607. returns true for variables that are explicitly declared to be global,

  1608. false for ones that are implicitly global.

  1609. (Contributed by Jeremy Hylton.)</p></li>

  1610. <li><p>The <a class="reference internal" href="../library/syslog.html#module-syslog" title="syslog: An interface to the Unix syslog library routines. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">syslog</span></code></a> module will now use the value of <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> as the

  1611. identifier instead of the previous default value of <code class="docutils literal notranslate"><span class="pre">'python'</span></code>.

  1612. (Changed by Sean Reifschneider; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8451">bpo-8451</a>.)</p></li>

  1613. <li><p>The <a class="reference internal" href="../library/sys.html#sys.version_info" title="sys.version_info"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.version_info</span></code></a> value is now a named tuple, with attributes

  1614. named <code class="xref py py-attr docutils literal notranslate"><span class="pre">major</span></code>, <code class="xref py py-attr docutils literal notranslate"><span class="pre">minor</span></code>, <code class="xref py py-attr docutils literal notranslate"><span class="pre">micro</span></code>,

  1615. <code class="xref py py-attr docutils literal notranslate"><span class="pre">releaselevel</span></code>, and <code class="xref py py-attr docutils literal notranslate"><span class="pre">serial</span></code>.  (Contributed by Ross

  1616. Light; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4285">bpo-4285</a>.)</p>

  1617. <p><a class="reference internal" href="../library/sys.html#sys.getwindowsversion" title="sys.getwindowsversion"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.getwindowsversion()</span></code></a> also returns a named tuple,

  1618. with attributes named <code class="xref py py-attr docutils literal notranslate"><span class="pre">major</span></code>, <code class="xref py py-attr docutils literal notranslate"><span class="pre">minor</span></code>, <code class="xref py py-attr docutils literal notranslate"><span class="pre">build</span></code>,

  1619. <code class="xref py py-attr docutils literal notranslate"><span class="pre">platform</span></code>, <code class="xref py py-attr docutils literal notranslate"><span class="pre">service_pack</span></code>, <code class="xref py py-attr docutils literal notranslate"><span class="pre">service_pack_major</span></code>,

  1620. <code class="xref py py-attr docutils literal notranslate"><span class="pre">service_pack_minor</span></code>, <code class="xref py py-attr docutils literal notranslate"><span class="pre">suite_mask</span></code>, and

  1621. <code class="xref py py-attr docutils literal notranslate"><span class="pre">product_type</span></code>.  (Contributed by Brian Curtin; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7766">bpo-7766</a>.)</p>

  1622. </li>

  1623. <li><p>The <a class="reference internal" href="../library/tarfile.html#module-tarfile" title="tarfile: Read and write tar-format archive files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">tarfile</span></code></a> module’s default error handling has changed, to

  1624. no longer suppress fatal errors.  The default error level was previously 0,

  1625. which meant that errors would only result in a message being written to the

  1626. debug log, but because the debug log is not activated by default,

  1627. these errors go unnoticed.  The default error level is now 1,

  1628. which raises an exception if there’s an error.

  1629. (Changed by Lars Gustäbel; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7357">bpo-7357</a>.)</p>

  1630. <p><a class="reference internal" href="../library/tarfile.html#module-tarfile" title="tarfile: Read and write tar-format archive files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">tarfile</span></code></a> now supports filtering the <a class="reference internal" href="../library/tarfile.html#tarfile.TarInfo" title="tarfile.TarInfo"><code class="xref py py-class docutils literal notranslate"><span class="pre">TarInfo</span></code></a>

  1631. objects being added to a tar file.  When you call <a class="reference internal" href="../library/tarfile.html#tarfile.TarFile.add" title="tarfile.TarFile.add"><code class="xref py py-meth docutils literal notranslate"><span class="pre">add()</span></code></a>,

  1632. you may supply an optional <em>filter</em> argument

  1633. that’s a callable.  The <em>filter</em> callable will be passed the

  1634. <a class="reference internal" href="../library/tarfile.html#tarfile.TarInfo" title="tarfile.TarInfo"><code class="xref py py-class docutils literal notranslate"><span class="pre">TarInfo</span></code></a> for every file being added, and can modify and return it.

  1635. If the callable returns <code class="docutils literal notranslate"><span class="pre">None</span></code>, the file will be excluded from the

  1636. resulting archive.  This is more powerful than the existing

  1637. <em>exclude</em> argument, which has therefore been deprecated.

  1638. (Added by Lars Gustäbel; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6856">bpo-6856</a>.)

  1639. The <a class="reference internal" href="../library/tarfile.html#tarfile.TarFile" title="tarfile.TarFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">TarFile</span></code></a> class also now supports the context management protocol.

  1640. (Added by Lars Gustäbel; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7232">bpo-7232</a>.)</p>

  1641. </li>

  1642. <li><p>The <a class="reference internal" href="../library/threading.html#threading.Event.wait" title="threading.Event.wait"><code class="xref py py-meth docutils literal notranslate"><span class="pre">wait()</span></code></a> method of the <a class="reference internal" href="../library/threading.html#threading.Event" title="threading.Event"><code class="xref py py-class docutils literal notranslate"><span class="pre">threading.Event</span></code></a> class

  1643. now returns the internal flag on exit.  This means the method will usually

  1644. return true because <a class="reference internal" href="../library/threading.html#threading.Event.wait" title="threading.Event.wait"><code class="xref py py-meth docutils literal notranslate"><span class="pre">wait()</span></code></a> is supposed to block until the

  1645. internal flag becomes true.  The return value will only be false if

  1646. a timeout was provided and the operation timed out.

  1647. (Contributed by Tim Lesher; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1674032">bpo-1674032</a>.)</p></li>

  1648. <li><p>The Unicode database provided by the <a class="reference internal" href="../library/unicodedata.html#module-unicodedata" title="unicodedata: Access the Unicode Database."><code class="xref py py-mod docutils literal notranslate"><span class="pre">unicodedata</span></code></a> module is

  1649. now used internally to determine which characters are numeric,

  1650. whitespace, or represent line breaks.  The database also

  1651. includes information from the <code class="file docutils literal notranslate"><span class="pre">Unihan.txt</span></code> data file (patch

  1652. by Anders Chrigström and Amaury Forgeot d’Arc; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1571184">bpo-1571184</a>)

  1653. and has been updated to version 5.2.0 (updated by

  1654. Florent Xicluna; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8024">bpo-8024</a>).</p></li>

  1655. <li><p>The <a class="reference internal" href="../library/urllib.parse.html#module-urllib.parse" title="urllib.parse: Parse URLs into or assemble them from components."><code class="xref py py-mod docutils literal notranslate"><span class="pre">urlparse</span></code></a> module’s <a class="reference internal" href="../library/urllib.parse.html#urllib.parse.urlsplit" title="urllib.parse.urlsplit"><code class="xref py py-func docutils literal notranslate"><span class="pre">urlsplit()</span></code></a> now handles

  1656. unknown URL schemes in a fashion compliant with <span class="target" id="index-9"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc3986.html"><strong>RFC 3986</strong></a>: if the

  1657. URL is of the form <code class="docutils literal notranslate"><span class="pre">&quot;&lt;something&gt;://...&quot;</span></code>, the text before the

  1658. <code class="docutils literal notranslate"><span class="pre">://</span></code> is treated as the scheme, even if it’s a made-up scheme that

  1659. the module doesn’t know about.  This change may break code that

  1660. worked around the old behaviour.  For example, Python 2.6.4 or 2.5

  1661. will return the following:</p>

  1662. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">urlparse</span>

  1663. <span class="gp">&gt;&gt;&gt; </span><span class="n">urlparse</span><span class="o">.</span><span class="n">urlsplit</span><span class="p">(</span><span class="s1">&#39;invented://host/filename?query&#39;</span><span class="p">)</span>

  1664. <span class="go">(&#39;invented&#39;, &#39;&#39;, &#39;//host/filename?query&#39;, &#39;&#39;, &#39;&#39;)</span>

  1665. </pre></div>

  1666. </div>

  1667. <p>Python 2.7 (and Python 2.6.5) will return:</p>

  1668. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">urlparse</span>

  1669. <span class="gp">&gt;&gt;&gt; </span><span class="n">urlparse</span><span class="o">.</span><span class="n">urlsplit</span><span class="p">(</span><span class="s1">&#39;invented://host/filename?query&#39;</span><span class="p">)</span>

  1670. <span class="go">(&#39;invented&#39;, &#39;host&#39;, &#39;/filename?query&#39;, &#39;&#39;, &#39;&#39;)</span>

  1671. </pre></div>

  1672. </div>

  1673. <p>(Python 2.7 actually produces slightly different output, since it

  1674. returns a named tuple instead of a standard tuple.)</p>

  1675. <p>The <a class="reference internal" href="../library/urllib.parse.html#module-urllib.parse" title="urllib.parse: Parse URLs into or assemble them from components."><code class="xref py py-mod docutils literal notranslate"><span class="pre">urlparse</span></code></a> module also supports IPv6 literal addresses as defined by

  1676. <span class="target" id="index-10"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc2732.html"><strong>RFC 2732</strong></a> (contributed by Senthil Kumaran; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2987">bpo-2987</a>).</p>

  1677. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">urlparse</span><span class="o">.</span><span class="n">urlparse</span><span class="p">(</span><span class="s1">&#39;http://[1080::8:800:200C:417A]/foo&#39;</span><span class="p">)</span>

  1678. <span class="go">ParseResult(scheme=&#39;http&#39;, netloc=&#39;[1080::8:800:200C:417A]&#39;,</span>

  1679. <span class="go">            path=&#39;/foo&#39;, params=&#39;&#39;, query=&#39;&#39;, fragment=&#39;&#39;)</span>

  1680. </pre></div>

  1681. </div>

  1682. </li>

  1683. <li><p>New class: the <a class="reference internal" href="../library/weakref.html#weakref.WeakSet" title="weakref.WeakSet"><code class="xref py py-class docutils literal notranslate"><span class="pre">WeakSet</span></code></a> class in the <a class="reference internal" href="../library/weakref.html#module-weakref" title="weakref: Support for weak references and weak dictionaries."><code class="xref py py-mod docutils literal notranslate"><span class="pre">weakref</span></code></a>

  1684. module is a set that only holds weak references to its elements; elements

  1685. will be removed once there are no references pointing to them.

  1686. (Originally implemented in Python 3.x by Raymond Hettinger, and backported

  1687. to 2.7 by Michael Foord.)</p></li>

  1688. <li><p>The <a class="reference internal" href="../library/xml.etree.elementtree.html#module-xml.etree.ElementTree" title="xml.etree.ElementTree: Implementation of the ElementTree API."><code class="xref py py-mod docutils literal notranslate"><span class="pre">xml.etree.ElementTree</span></code></a> library, no longer escapes

  1689. ampersands and angle brackets when outputting an XML processing

  1690. instruction (which looks like <code class="docutils literal notranslate"><span class="pre">&lt;?xml-stylesheet</span> <span class="pre">href=&quot;#style1&quot;?&gt;</span></code>)

  1691. or comment (which looks like <code class="docutils literal notranslate"><span class="pre">&lt;!--</span> <span class="pre">comment</span> <span class="pre">--&gt;</span></code>).

  1692. (Patch by Neil Muller; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2746">bpo-2746</a>.)</p></li>

  1693. <li><p>The XML-RPC client and server, provided by the <a class="reference internal" href="../library/xmlrpc.client.html#module-xmlrpc.client" title="xmlrpc.client: XML-RPC client access."><code class="xref py py-mod docutils literal notranslate"><span class="pre">xmlrpclib</span></code></a> and

  1694. <a class="reference internal" href="../library/xmlrpc.server.html#module-xmlrpc.server" title="xmlrpc.server: Basic XML-RPC server implementations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">SimpleXMLRPCServer</span></code></a> modules, have improved performance by

  1695. supporting HTTP/1.1 keep-alive and by optionally using gzip encoding

  1696. to compress the XML being exchanged.  The gzip compression is

  1697. controlled by the <code class="xref py py-attr docutils literal notranslate"><span class="pre">encode_threshold</span></code> attribute of

  1698. <a class="reference internal" href="../library/xmlrpc.server.html#xmlrpc.server.SimpleXMLRPCRequestHandler" title="xmlrpc.server.SimpleXMLRPCRequestHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">SimpleXMLRPCRequestHandler</span></code></a>, which contains a size in bytes;

  1699. responses larger than this will be compressed.

  1700. (Contributed by Kristján Valur Jónsson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6267">bpo-6267</a>.)</p></li>

  1701. <li><p>The <a class="reference internal" href="../library/zipfile.html#module-zipfile" title="zipfile: Read and write ZIP-format archive files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">zipfile</span></code></a> module’s <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile" title="zipfile.ZipFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZipFile</span></code></a> now supports the context

  1702. management protocol, so you can write <code class="docutils literal notranslate"><span class="pre">with</span> <span class="pre">zipfile.ZipFile(...)</span> <span class="pre">as</span> <span class="pre">f:</span></code>.

  1703. (Contributed by Brian Curtin; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5511">bpo-5511</a>.)</p>

  1704. <p><a class="reference internal" href="../library/zipfile.html#module-zipfile" title="zipfile: Read and write ZIP-format archive files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">zipfile</span></code></a> now also supports archiving empty directories and

  1705. extracts them correctly.  (Fixed by Kuba Wieczorek; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4710">bpo-4710</a>.)

  1706. Reading files out of an archive is faster, and interleaving

  1707. <a class="reference internal" href="../library/io.html#io.BufferedIOBase.read" title="io.BufferedIOBase.read"><code class="xref py py-meth docutils literal notranslate"><span class="pre">read()</span></code></a> and

  1708. <a class="reference internal" href="../library/io.html#io.IOBase.readline" title="io.IOBase.readline"><code class="xref py py-meth docutils literal notranslate"><span class="pre">readline()</span></code></a> now works correctly.

  1709. (Contributed by Nir Aides; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7610">bpo-7610</a>.)</p>

  1710. <p>The <a class="reference internal" href="../library/zipfile.html#zipfile.is_zipfile" title="zipfile.is_zipfile"><code class="xref py py-func docutils literal notranslate"><span class="pre">is_zipfile()</span></code></a> function now

  1711. accepts a file object, in addition to the path names accepted in earlier

  1712. versions.  (Contributed by Gabriel Genellina; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4756">bpo-4756</a>.)</p>

  1713. <p>The <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile.writestr" title="zipfile.ZipFile.writestr"><code class="xref py py-meth docutils literal notranslate"><span class="pre">writestr()</span></code></a> method now has an optional <em>compress_type</em> parameter

  1714. that lets you override the default compression method specified in the

  1715. <a class="reference internal" href="../library/zipfile.html#zipfile.ZipFile" title="zipfile.ZipFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">ZipFile</span></code></a> constructor.  (Contributed by Ronald Oussoren;

  1716. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6003">bpo-6003</a>.)</p>

  1717. </li>

  1718. </ul>

  1719. <section id="new-module-importlib">

  1720. <span id="importlib-section"></span><h3>New module: importlib<a class="headerlink" href="#new-module-importlib" title="Link to this heading">¶</a></h3>

  1721. <p>Python 3.1 includes the <a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib</span></code></a> package, a re-implementation

  1722. of the logic underlying Python’s <a class="reference internal" href="../reference/simple_stmts.html#import"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">import</span></code></a> statement.

  1723. <a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib</span></code></a> is useful for implementors of Python interpreters and

  1724. to users who wish to write new importers that can participate in the

  1725. import process.  Python 2.7 doesn’t contain the complete

  1726. <a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib</span></code></a> package, but instead has a tiny subset that contains

  1727. a single function, <a class="reference internal" href="../library/importlib.html#importlib.import_module" title="importlib.import_module"><code class="xref py py-func docutils literal notranslate"><span class="pre">import_module()</span></code></a>.</p>

  1728. <p><code class="docutils literal notranslate"><span class="pre">import_module(name,</span> <span class="pre">package=None)</span></code> imports a module.  <em>name</em> is

  1729. a string containing the module or package’s name.  It’s possible to do

  1730. relative imports by providing a string that begins with a <code class="docutils literal notranslate"><span class="pre">.</span></code>

  1731. character, such as <code class="docutils literal notranslate"><span class="pre">..utils.errors</span></code>.  For relative imports, the

  1732. <em>package</em> argument must be provided and is the name of the package that

  1733. will be used as the anchor for

  1734. the relative import.  <a class="reference internal" href="../library/importlib.html#importlib.import_module" title="importlib.import_module"><code class="xref py py-func docutils literal notranslate"><span class="pre">import_module()</span></code></a> both inserts the imported

  1735. module into <code class="docutils literal notranslate"><span class="pre">sys.modules</span></code> and returns the module object.</p>

  1736. <p>Here are some examples:</p>

  1737. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">importlib</span> <span class="kn">import</span> <span class="n">import_module</span>

  1738. <span class="gp">&gt;&gt;&gt; </span><span class="n">anydbm</span> <span class="o">=</span> <span class="n">import_module</span><span class="p">(</span><span class="s1">&#39;anydbm&#39;</span><span class="p">)</span>  <span class="c1"># Standard absolute import</span>

  1739. <span class="gp">&gt;&gt;&gt; </span><span class="n">anydbm</span>

  1740. <span class="go">&lt;module &#39;anydbm&#39; from &#39;/p/python/Lib/anydbm.py&#39;&gt;</span>

  1741. <span class="gp">&gt;&gt;&gt; </span><span class="c1"># Relative import</span>

  1742. <span class="gp">&gt;&gt;&gt; </span><span class="n">file_util</span> <span class="o">=</span> <span class="n">import_module</span><span class="p">(</span><span class="s1">&#39;..file_util&#39;</span><span class="p">,</span> <span class="s1">&#39;distutils.command&#39;</span><span class="p">)</span>

  1743. <span class="gp">&gt;&gt;&gt; </span><span class="n">file_util</span>

  1744. <span class="go">&lt;module &#39;distutils.file_util&#39; from &#39;/python/Lib/distutils/file_util.pyc&#39;&gt;</span>

  1745. </pre></div>

  1746. </div>

  1747. <p><a class="reference internal" href="../library/importlib.html#module-importlib" title="importlib: The implementation of the import machinery."><code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib</span></code></a> was implemented by Brett Cannon and introduced in

  1748. Python 3.1.</p>

  1749. </section>

  1750. <section id="new-module-sysconfig">

  1751. <h3>New module: sysconfig<a class="headerlink" href="#new-module-sysconfig" title="Link to this heading">¶</a></h3>

  1752. <p>The <a class="reference internal" href="../library/sysconfig.html#module-sysconfig" title="sysconfig: Python's configuration information"><code class="xref py py-mod docutils literal notranslate"><span class="pre">sysconfig</span></code></a> module has been pulled out of the Distutils

  1753. package, becoming a new top-level module in its own right.

  1754. <a class="reference internal" href="../library/sysconfig.html#module-sysconfig" title="sysconfig: Python's configuration information"><code class="xref py py-mod docutils literal notranslate"><span class="pre">sysconfig</span></code></a> provides functions for getting information about

  1755. Python’s build process: compiler switches, installation paths, the

  1756. platform name, and whether Python is running from its source

  1757. directory.</p>

  1758. <p>Some of the functions in the module are:</p>

  1759. <ul class="simple">

  1760. <li><p><a class="reference internal" href="../library/sysconfig.html#sysconfig.get_config_var" title="sysconfig.get_config_var"><code class="xref py py-func docutils literal notranslate"><span class="pre">get_config_var()</span></code></a> returns variables from Python’s

  1761. Makefile and the <code class="file docutils literal notranslate"><span class="pre">pyconfig.h</span></code> file.</p></li>

  1762. <li><p><a class="reference internal" href="../library/sysconfig.html#sysconfig.get_config_vars" title="sysconfig.get_config_vars"><code class="xref py py-func docutils literal notranslate"><span class="pre">get_config_vars()</span></code></a> returns a dictionary containing

  1763. all of the configuration variables.</p></li>

  1764. <li><p><a class="reference internal" href="../library/sysconfig.html#sysconfig.get_path" title="sysconfig.get_path"><code class="xref py py-func docutils literal notranslate"><span class="pre">get_path()</span></code></a> returns the configured path for

  1765. a particular type of module: the standard library,

  1766. site-specific modules, platform-specific modules, etc.</p></li>

  1767. <li><p><a class="reference internal" href="../library/sysconfig.html#sysconfig.is_python_build" title="sysconfig.is_python_build"><code class="xref py py-func docutils literal notranslate"><span class="pre">is_python_build()</span></code></a> returns true if you’re running a

  1768. binary from a Python source tree, and false otherwise.</p></li>

  1769. </ul>

  1770. <p>Consult the <a class="reference internal" href="../library/sysconfig.html#module-sysconfig" title="sysconfig: Python's configuration information"><code class="xref py py-mod docutils literal notranslate"><span class="pre">sysconfig</span></code></a> documentation for more details and for

  1771. a complete list of functions.</p>

  1772. <p>The Distutils package and <a class="reference internal" href="../library/sysconfig.html#module-sysconfig" title="sysconfig: Python's configuration information"><code class="xref py py-mod docutils literal notranslate"><span class="pre">sysconfig</span></code></a> are now maintained by Tarek

  1773. Ziadé, who has also started a Distutils2 package (source repository at

  1774. <a class="reference external" href="https://hg.python.org/distutils2/">https://hg.python.org/distutils2/</a>) for developing a next-generation

  1775. version of Distutils.</p>

  1776. </section>

  1777. <section id="ttk-themed-widgets-for-tk">

  1778. <h3>ttk: Themed Widgets for Tk<a class="headerlink" href="#ttk-themed-widgets-for-tk" title="Link to this heading">¶</a></h3>

  1779. <p>Tcl/Tk 8.5 includes a set of themed widgets that re-implement basic Tk

  1780. widgets but have a more customizable appearance and can therefore more

  1781. closely resemble the native platform’s widgets.  This widget

  1782. set was originally called Tile, but was renamed to Ttk (for “themed Tk”)

  1783. on being added to Tcl/Tck release 8.5.</p>

  1784. <p>To learn more, read the <a class="reference internal" href="../library/tkinter.ttk.html#module-tkinter.ttk" title="tkinter.ttk: Tk themed widget set"><code class="xref py py-mod docutils literal notranslate"><span class="pre">ttk</span></code></a> module documentation.  You may also

  1785. wish to read the Tcl/Tk manual page describing the

  1786. Ttk theme engine, available at

  1787. <a class="reference external" href="https://www.tcl.tk/man/tcl8.5/TkCmd/ttk_intro.html">https://www.tcl.tk/man/tcl8.5/TkCmd/ttk_intro.html</a>. Some

  1788. screenshots of the Python/Ttk code in use are at

  1789. <a class="reference external" href="https://code.google.com/archive/p/python-ttk/wikis/Screenshots.wiki">https://code.google.com/archive/p/python-ttk/wikis/Screenshots.wiki</a>.</p>

  1790. <p>The <a class="reference internal" href="../library/tkinter.ttk.html#module-tkinter.ttk" title="tkinter.ttk: Tk themed widget set"><code class="xref py py-mod docutils literal notranslate"><span class="pre">tkinter.ttk</span></code></a> module was written by Guilherme Polo and added in

  1791. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2983">bpo-2983</a>.  An alternate version called <code class="docutils literal notranslate"><span class="pre">Tile.py</span></code>, written by

  1792. Martin Franklin and maintained by Kevin Walzer, was proposed for

  1793. inclusion in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2618">bpo-2618</a>, but the authors argued that Guilherme

  1794. Polo’s work was more comprehensive.</p>

  1795. </section>

  1796. <section id="updated-module-unittest">

  1797. <span id="unittest-section"></span><h3>Updated module: unittest<a class="headerlink" href="#updated-module-unittest" title="Link to this heading">¶</a></h3>

  1798. <p>The <a class="reference internal" href="../library/unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate"><span class="pre">unittest</span></code></a> module was greatly enhanced; many

  1799. new features were added.  Most of these features were implemented

  1800. by Michael Foord, unless otherwise noted.  The enhanced version of

  1801. the module is downloadable separately for use with Python versions 2.4 to 2.6,

  1802. packaged as the <code class="xref py py-mod docutils literal notranslate"><span class="pre">unittest2</span></code> package, from

  1803. <a class="reference external" href="https://pypi.org/project/unittest2">https://pypi.org/project/unittest2</a>.</p>

  1804. <p>When used from the command line, the module can automatically discover

  1805. tests.  It’s not as fancy as <a class="reference external" href="https://pytest.org">py.test</a> or

  1806. <a class="reference external" href="https://nose.readthedocs.io/">nose</a>, but provides a

  1807. simple way to run tests kept within a set of package directories.  For example,

  1808. the following command will search the <code class="file docutils literal notranslate"><span class="pre">test/</span></code> subdirectory for

  1809. any importable test files named <code class="docutils literal notranslate"><span class="pre">test*.py</span></code>:</p>

  1810. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">python</span> <span class="o">-</span><span class="n">m</span> <span class="n">unittest</span> <span class="n">discover</span> <span class="o">-</span><span class="n">s</span> <span class="n">test</span>

  1811. </pre></div>

  1812. </div>

  1813. <p>Consult the <a class="reference internal" href="../library/unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate"><span class="pre">unittest</span></code></a> module documentation for more details.

  1814. (Developed in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6001">bpo-6001</a>.)</p>

  1815. <p>The <a class="reference internal" href="../library/unittest.html#unittest.main" title="unittest.main"><code class="xref py py-func docutils literal notranslate"><span class="pre">main()</span></code></a> function supports some other new options:</p>

  1816. <ul>

  1817. <li><p><a class="reference internal" href="../library/unittest.html#cmdoption-unittest-b"><code class="xref std std-option docutils literal notranslate"><span class="pre">-b</span></code></a> or <code class="xref std std-option docutils literal notranslate"><span class="pre">--buffer</span></code> will buffer the standard output

  1818. and standard error streams during each test.  If the test passes,

  1819. any resulting output will be discarded; on failure, the buffered

  1820. output will be displayed.</p></li>

  1821. <li><p><a class="reference internal" href="../library/unittest.html#cmdoption-unittest-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">-c</span></code></a> or <code class="xref std std-option docutils literal notranslate"><span class="pre">--catch</span></code> will cause the control-C interrupt

  1822. to be handled more gracefully.  Instead of interrupting the test

  1823. process immediately, the currently running test will be completed

  1824. and then the partial results up to the interruption will be reported.

  1825. If you’re impatient, a second press of control-C will cause an immediate

  1826. interruption.</p>

  1827. <p>This control-C handler tries to avoid causing problems when the code

  1828. being tested or the tests being run have defined a signal handler of

  1829. their own, by noticing that a signal handler was already set and

  1830. calling it.  If this doesn’t work for you, there’s a

  1831. <a class="reference internal" href="../library/unittest.html#unittest.removeHandler" title="unittest.removeHandler"><code class="xref py py-func docutils literal notranslate"><span class="pre">removeHandler()</span></code></a> decorator that can be used to mark tests that

  1832. should have the control-C handling disabled.</p>

  1833. </li>

  1834. <li><p><a class="reference internal" href="../library/unittest.html#cmdoption-unittest-f"><code class="xref std std-option docutils literal notranslate"><span class="pre">-f</span></code></a> or <code class="xref std std-option docutils literal notranslate"><span class="pre">--failfast</span></code> makes

  1835. test execution stop immediately when a test fails instead of

  1836. continuing to execute further tests.  (Suggested by Cliff Dyer and

  1837. implemented by Michael Foord; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8074">bpo-8074</a>.)</p></li>

  1838. </ul>

  1839. <p>The progress messages now show ‘x’ for expected failures

  1840. and ‘u’ for unexpected successes when run in verbose mode.

  1841. (Contributed by Benjamin Peterson.)</p>

  1842. <p>Test cases can raise the <a class="reference internal" href="../library/unittest.html#unittest.SkipTest" title="unittest.SkipTest"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SkipTest</span></code></a> exception to skip a

  1843. test (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1034053">bpo-1034053</a>).</p>

  1844. <p>The error messages for <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertEqual()</span></code></a>,

  1845. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertTrue" title="unittest.TestCase.assertTrue"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertTrue()</span></code></a>, and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertFalse" title="unittest.TestCase.assertFalse"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertFalse()</span></code></a>

  1846. failures now provide more information.  If you set the

  1847. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.longMessage" title="unittest.TestCase.longMessage"><code class="xref py py-attr docutils literal notranslate"><span class="pre">longMessage</span></code></a> attribute of your <a class="reference internal" href="../library/unittest.html#unittest.TestCase" title="unittest.TestCase"><code class="xref py py-class docutils literal notranslate"><span class="pre">TestCase</span></code></a> classes to

  1848. true, both the standard error message and any additional message you

  1849. provide will be printed for failures.  (Added by Michael Foord; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5663">bpo-5663</a>.)</p>

  1850. <p>The <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertRaises" title="unittest.TestCase.assertRaises"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertRaises()</span></code></a> method now

  1851. returns a context handler when called without providing a callable

  1852. object to run.  For example, you can write this:</p>

  1853. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">with</span> <span class="bp">self</span><span class="o">.</span><span class="n">assertRaises</span><span class="p">(</span><span class="ne">KeyError</span><span class="p">):</span>

  1854.     <span class="p">{}[</span><span class="s1">&#39;foo&#39;</span><span class="p">]</span>

  1855. </pre></div>

  1856. </div>

  1857. <p>(Implemented by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4444">bpo-4444</a>.)</p>

  1858. <p>Module- and class-level setup and teardown fixtures are now supported.

  1859. Modules can contain <code class="xref py py-func docutils literal notranslate"><span class="pre">setUpModule()</span></code> and <code class="xref py py-func docutils literal notranslate"><span class="pre">tearDownModule()</span></code>

  1860. functions.  Classes can have <a class="reference internal" href="../library/unittest.html#unittest.TestCase.setUpClass" title="unittest.TestCase.setUpClass"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setUpClass()</span></code></a> and

  1861. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.tearDownClass" title="unittest.TestCase.tearDownClass"><code class="xref py py-meth docutils literal notranslate"><span class="pre">tearDownClass()</span></code></a> methods that must be defined as class methods

  1862. (using <code class="docutils literal notranslate"><span class="pre">&#64;classmethod</span></code> or equivalent).  These functions and

  1863. methods are invoked when the test runner switches to a test case in a

  1864. different module or class.</p>

  1865. <p>The methods <a class="reference internal" href="../library/unittest.html#unittest.TestCase.addCleanup" title="unittest.TestCase.addCleanup"><code class="xref py py-meth docutils literal notranslate"><span class="pre">addCleanup()</span></code></a> and

  1866. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.doCleanups" title="unittest.TestCase.doCleanups"><code class="xref py py-meth docutils literal notranslate"><span class="pre">doCleanups()</span></code></a> were added.

  1867. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.addCleanup" title="unittest.TestCase.addCleanup"><code class="xref py py-meth docutils literal notranslate"><span class="pre">addCleanup()</span></code></a> lets you add cleanup functions that

  1868. will be called unconditionally (after <a class="reference internal" href="../library/unittest.html#unittest.TestCase.setUp" title="unittest.TestCase.setUp"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setUp()</span></code></a> if

  1869. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.setUp" title="unittest.TestCase.setUp"><code class="xref py py-meth docutils literal notranslate"><span class="pre">setUp()</span></code></a> fails, otherwise after <a class="reference internal" href="../library/unittest.html#unittest.TestCase.tearDown" title="unittest.TestCase.tearDown"><code class="xref py py-meth docutils literal notranslate"><span class="pre">tearDown()</span></code></a>). This allows

  1870. for much simpler resource allocation and deallocation during tests

  1871. (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5679">bpo-5679</a>).</p>

  1872. <p>A number of new methods were added that provide more specialized

  1873. tests.  Many of these methods were written by Google engineers

  1874. for use in their test suites; Gregory P. Smith, Michael Foord, and

  1875. GvR worked on merging them into Python’s version of <a class="reference internal" href="../library/unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate"><span class="pre">unittest</span></code></a>.</p>

  1876. <ul class="simple">

  1877. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIsNone" title="unittest.TestCase.assertIsNone"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertIsNone()</span></code></a> and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIsNotNone" title="unittest.TestCase.assertIsNotNone"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertIsNotNone()</span></code></a> take one

  1878. expression and verify that the result is or is not <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p></li>

  1879. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIs" title="unittest.TestCase.assertIs"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertIs()</span></code></a> and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIsNot" title="unittest.TestCase.assertIsNot"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertIsNot()</span></code></a>

  1880. take two values and check whether the two values evaluate to the same object or not.

  1881. (Added by Michael Foord; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2578">bpo-2578</a>.)</p></li>

  1882. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIsInstance" title="unittest.TestCase.assertIsInstance"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertIsInstance()</span></code></a> and

  1883. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertNotIsInstance" title="unittest.TestCase.assertNotIsInstance"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertNotIsInstance()</span></code></a> check whether

  1884. the resulting object is an instance of a particular class, or of

  1885. one of a tuple of classes.  (Added by Georg Brandl; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7031">bpo-7031</a>.)</p></li>

  1886. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertGreater" title="unittest.TestCase.assertGreater"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertGreater()</span></code></a>, <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertGreaterEqual" title="unittest.TestCase.assertGreaterEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertGreaterEqual()</span></code></a>,

  1887. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertLess" title="unittest.TestCase.assertLess"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertLess()</span></code></a>, and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertLessEqual" title="unittest.TestCase.assertLessEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertLessEqual()</span></code></a> compare

  1888. two quantities.</p></li>

  1889. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertMultiLineEqual" title="unittest.TestCase.assertMultiLineEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertMultiLineEqual()</span></code></a> compares two strings, and if they’re

  1890. not equal, displays a helpful comparison that highlights the

  1891. differences in the two strings.  This comparison is now used by

  1892. default when Unicode strings are compared with <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertEqual()</span></code></a>.</p></li>

  1893. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertRegex" title="unittest.TestCase.assertRegex"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertRegexpMatches()</span></code></a> and

  1894. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertNotRegex" title="unittest.TestCase.assertNotRegex"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertNotRegexpMatches()</span></code></a> checks whether the

  1895. first argument is a string matching or not matching the regular

  1896. expression provided as the second argument (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8038">bpo-8038</a>).</p></li>

  1897. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertRaisesRegex" title="unittest.TestCase.assertRaisesRegex"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertRaisesRegexp()</span></code></a> checks

  1898. whether a particular exception

  1899. is raised, and then also checks that the string representation of

  1900. the exception matches the provided regular expression.</p></li>

  1901. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertIn" title="unittest.TestCase.assertIn"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertIn()</span></code></a> and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertNotIn" title="unittest.TestCase.assertNotIn"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertNotIn()</span></code></a>

  1902. tests whether <em>first</em> is or is not in  <em>second</em>.</p></li>

  1903. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertCountEqual" title="unittest.TestCase.assertCountEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertItemsEqual()</span></code></a> tests whether two provided sequences

  1904. contain the same elements.</p></li>

  1905. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertSetEqual" title="unittest.TestCase.assertSetEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertSetEqual()</span></code></a> compares whether two sets are equal, and

  1906. only reports the differences between the sets in case of error.</p></li>

  1907. <li><p>Similarly, <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertListEqual" title="unittest.TestCase.assertListEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertListEqual()</span></code></a> and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertTupleEqual" title="unittest.TestCase.assertTupleEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertTupleEqual()</span></code></a>

  1908. compare the specified types and explain any differences without necessarily

  1909. printing their full values; these methods are now used by default

  1910. when comparing lists and tuples using <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertEqual()</span></code></a>.

  1911. More generally, <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertSequenceEqual" title="unittest.TestCase.assertSequenceEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertSequenceEqual()</span></code></a> compares two sequences

  1912. and can optionally check whether both sequences are of a

  1913. particular type.</p></li>

  1914. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertDictEqual" title="unittest.TestCase.assertDictEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertDictEqual()</span></code></a> compares two dictionaries and reports the

  1915. differences; it’s now used by default when you compare two dictionaries

  1916. using <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertEqual()</span></code></a>.  <code class="xref py py-meth docutils literal notranslate"><span class="pre">assertDictContainsSubset()</span></code> checks whether

  1917. all of the key/value pairs in <em>first</em> are found in <em>second</em>.</p></li>

  1918. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertAlmostEqual" title="unittest.TestCase.assertAlmostEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertAlmostEqual()</span></code></a> and <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertNotAlmostEqual" title="unittest.TestCase.assertNotAlmostEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertNotAlmostEqual()</span></code></a> test

  1919. whether <em>first</em> and <em>second</em> are approximately equal.  This method

  1920. can either round their difference to an optionally specified number

  1921. of <em>places</em> (the default is 7) and compare it to zero, or require

  1922. the difference to be smaller than a supplied <em>delta</em> value.</p></li>

  1923. <li><p><a class="reference internal" href="../library/unittest.html#unittest.TestLoader.loadTestsFromName" title="unittest.TestLoader.loadTestsFromName"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loadTestsFromName()</span></code></a> properly honors the

  1924. <a class="reference internal" href="../library/unittest.html#unittest.TestLoader.suiteClass" title="unittest.TestLoader.suiteClass"><code class="xref py py-attr docutils literal notranslate"><span class="pre">suiteClass</span></code></a> attribute of

  1925. the <a class="reference internal" href="../library/unittest.html#unittest.TestLoader" title="unittest.TestLoader"><code class="xref py py-class docutils literal notranslate"><span class="pre">TestLoader</span></code></a>. (Fixed by Mark Roddy; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6866">bpo-6866</a>.)</p></li>

  1926. <li><p>A new hook lets you extend the <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertEqual" title="unittest.TestCase.assertEqual"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertEqual()</span></code></a> method to handle

  1927. new data types.  The <a class="reference internal" href="../library/unittest.html#unittest.TestCase.addTypeEqualityFunc" title="unittest.TestCase.addTypeEqualityFunc"><code class="xref py py-meth docutils literal notranslate"><span class="pre">addTypeEqualityFunc()</span></code></a> method takes a type

  1928. object and a function. The function will be used when both of the

  1929. objects being compared are of the specified type.  This function

  1930. should compare the two objects and raise an exception if they don’t

  1931. match; it’s a good idea for the function to provide additional

  1932. information about why the two objects aren’t matching, much as the new

  1933. sequence comparison methods do.</p></li>

  1934. </ul>

  1935. <p><a class="reference internal" href="../library/unittest.html#unittest.main" title="unittest.main"><code class="xref py py-func docutils literal notranslate"><span class="pre">unittest.main()</span></code></a> now takes an optional <code class="docutils literal notranslate"><span class="pre">exit</span></code> argument.  If

  1936. false, <a class="reference internal" href="../library/unittest.html#unittest.main" title="unittest.main"><code class="xref py py-func docutils literal notranslate"><span class="pre">main()</span></code></a> doesn’t call <a class="reference internal" href="../library/sys.html#sys.exit" title="sys.exit"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.exit()</span></code></a>, allowing

  1937. <a class="reference internal" href="../library/unittest.html#unittest.main" title="unittest.main"><code class="xref py py-func docutils literal notranslate"><span class="pre">main()</span></code></a> to be used from the interactive interpreter.

  1938. (Contributed by J. Pablo Fernández; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3379">bpo-3379</a>.)</p>

  1939. <p><a class="reference internal" href="../library/unittest.html#unittest.TestResult" title="unittest.TestResult"><code class="xref py py-class docutils literal notranslate"><span class="pre">TestResult</span></code></a> has new <a class="reference internal" href="../library/unittest.html#unittest.TestResult.startTestRun" title="unittest.TestResult.startTestRun"><code class="xref py py-meth docutils literal notranslate"><span class="pre">startTestRun()</span></code></a> and

  1940. <a class="reference internal" href="../library/unittest.html#unittest.TestResult.stopTestRun" title="unittest.TestResult.stopTestRun"><code class="xref py py-meth docutils literal notranslate"><span class="pre">stopTestRun()</span></code></a> methods that are called immediately before

  1941. and after a test run.  (Contributed by Robert Collins; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5728">bpo-5728</a>.)</p>

  1942. <p>With all these changes, the <code class="file docutils literal notranslate"><span class="pre">unittest.py</span></code> was becoming awkwardly

  1943. large, so the module was turned into a package and the code split into

  1944. several files (by Benjamin Peterson).  This doesn’t affect how the

  1945. module is imported or used.</p>

  1946. <div class="admonition seealso">

  1947. <p class="admonition-title">See also</p>

  1948. <dl class="simple">

  1949. <dt><a class="reference external" href="https://web.archive.org/web/20210619163128/http://www.voidspace.org.uk/python/articles/unittest2.shtml">https://web.archive.org/web/20210619163128/http://www.voidspace.org.uk/python/articles/unittest2.shtml</a></dt><dd><p>Describes the new features, how to use them, and the

  1950. rationale for various design decisions.  (By Michael Foord.)</p>

  1951. </dd>

  1952. </dl>

  1953. </div>

  1954. </section>

  1955. <section id="updated-module-elementtree-1-3">

  1956. <span id="elementtree-section"></span><h3>Updated module: ElementTree 1.3<a class="headerlink" href="#updated-module-elementtree-1-3" title="Link to this heading">¶</a></h3>

  1957. <p>The version of the ElementTree library included with Python was updated to

  1958. version 1.3.  Some of the new features are:</p>

  1959. <ul>

  1960. <li><p>The various parsing functions now take a <em>parser</em> keyword argument

  1961. giving an <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.XMLParser" title="xml.etree.ElementTree.XMLParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">XMLParser</span></code></a> instance that will

  1962. be used.  This makes it possible to override the file’s internal encoding:</p>

  1963. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">p</span> <span class="o">=</span> <span class="n">ET</span><span class="o">.</span><span class="n">XMLParser</span><span class="p">(</span><span class="n">encoding</span><span class="o">=</span><span class="s1">&#39;utf-8&#39;</span><span class="p">)</span>

  1964. <span class="n">t</span> <span class="o">=</span> <span class="n">ET</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span><span class="s2">&quot;&quot;&quot;&lt;root/&gt;&quot;&quot;&quot;</span><span class="p">,</span> <span class="n">parser</span><span class="o">=</span><span class="n">p</span><span class="p">)</span>

  1965. </pre></div>

  1966. </div>

  1967. <p>Errors in parsing XML now raise a <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.ParseError" title="xml.etree.ElementTree.ParseError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ParseError</span></code></a> exception, whose

  1968. instances have a <code class="xref py py-attr docutils literal notranslate"><span class="pre">position</span></code> attribute

  1969. containing a (<em>line</em>, <em>column</em>) tuple giving the location of the problem.</p>

  1970. </li>

  1971. <li><p>ElementTree’s code for converting trees to a string has been

  1972. significantly reworked, making it roughly twice as fast in many

  1973. cases.  The <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.ElementTree.write" title="xml.etree.ElementTree.ElementTree.write"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ElementTree.write()</span></code></a>

  1974. and <code class="xref py py-meth docutils literal notranslate"><span class="pre">Element.write()</span></code> methods now have a <em>method</em> parameter that can be

  1975. “xml” (the default), “html”, or “text”.  HTML mode will output empty

  1976. elements as <code class="docutils literal notranslate"><span class="pre">&lt;empty&gt;&lt;/empty&gt;</span></code> instead of <code class="docutils literal notranslate"><span class="pre">&lt;empty/&gt;</span></code>, and text

  1977. mode will skip over elements and only output the text chunks.  If

  1978. you set the <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element.tag" title="xml.etree.ElementTree.Element.tag"><code class="xref py py-attr docutils literal notranslate"><span class="pre">tag</span></code></a> attribute of an

  1979. element to <code class="docutils literal notranslate"><span class="pre">None</span></code> but

  1980. leave its children in place, the element will be omitted when the

  1981. tree is written out, so you don’t need to do more extensive rearrangement

  1982. to remove a single element.</p>

  1983. <p>Namespace handling has also been improved.  All <code class="docutils literal notranslate"><span class="pre">xmlns:&lt;whatever&gt;</span></code>

  1984. declarations are now output on the root element, not scattered throughout

  1985. the resulting XML.  You can set the default namespace for a tree

  1986. by setting the <code class="xref py py-attr docutils literal notranslate"><span class="pre">default_namespace</span></code> attribute and can

  1987. register new prefixes with <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.register_namespace" title="xml.etree.ElementTree.register_namespace"><code class="xref py py-meth docutils literal notranslate"><span class="pre">register_namespace()</span></code></a>.  In XML mode,

  1988. you can use the true/false <em>xml_declaration</em> parameter to suppress the

  1989. XML declaration.</p>

  1990. </li>

  1991. <li><p>New <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element" title="xml.etree.ElementTree.Element"><code class="xref py py-class docutils literal notranslate"><span class="pre">Element</span></code></a> method:

  1992. <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element.extend" title="xml.etree.ElementTree.Element.extend"><code class="xref py py-meth docutils literal notranslate"><span class="pre">extend()</span></code></a> appends the items from a

  1993. sequence to the element’s children.  Elements themselves behave like

  1994. sequences, so it’s easy to move children from one element to

  1995. another:</p>

  1996. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">xml.etree</span> <span class="kn">import</span> <span class="n">ElementTree</span> <span class="k">as</span> <span class="n">ET</span>

  1997. 

  1998. <span class="n">t</span> <span class="o">=</span> <span class="n">ET</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span><span class="s2">&quot;&quot;&quot;&lt;list&gt;</span>

  1999. <span class="s2">  &lt;item&gt;1&lt;/item&gt; &lt;item&gt;2&lt;/item&gt;  &lt;item&gt;3&lt;/item&gt;</span>

  2000. <span class="s2">&lt;/list&gt;&quot;&quot;&quot;</span><span class="p">)</span>

  2001. <span class="n">new</span> <span class="o">=</span> <span class="n">ET</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span><span class="s1">&#39;&lt;root/&gt;&#39;</span><span class="p">)</span>

  2002. <span class="n">new</span><span class="o">.</span><span class="n">extend</span><span class="p">(</span><span class="n">t</span><span class="p">)</span>

  2003. 

  2004. <span class="c1"># Outputs &lt;root&gt;&lt;item&gt;1&lt;/item&gt;...&lt;/root&gt;</span>

  2005. <span class="nb">print</span> <span class="n">ET</span><span class="o">.</span><span class="n">tostring</span><span class="p">(</span><span class="n">new</span><span class="p">)</span>

  2006. </pre></div>

  2007. </div>

  2008. </li>

  2009. <li><p>New <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element" title="xml.etree.ElementTree.Element"><code class="xref py py-class docutils literal notranslate"><span class="pre">Element</span></code></a> method:

  2010. <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element.iter" title="xml.etree.ElementTree.Element.iter"><code class="xref py py-meth docutils literal notranslate"><span class="pre">iter()</span></code></a> yields the children of the

  2011. element as a generator.  It’s also possible to write <code class="docutils literal notranslate"><span class="pre">for</span> <span class="pre">child</span> <span class="pre">in</span>

  2012. <span class="pre">elem:</span></code> to loop over an element’s children.  The existing method

  2013. <code class="xref py py-meth docutils literal notranslate"><span class="pre">getiterator()</span></code> is now deprecated, as is <code class="xref py py-meth docutils literal notranslate"><span class="pre">getchildren()</span></code>

  2014. which constructs and returns a list of children.</p></li>

  2015. <li><p>New <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element" title="xml.etree.ElementTree.Element"><code class="xref py py-class docutils literal notranslate"><span class="pre">Element</span></code></a> method:

  2016. <a class="reference internal" href="../library/xml.etree.elementtree.html#xml.etree.ElementTree.Element.itertext" title="xml.etree.ElementTree.Element.itertext"><code class="xref py py-meth docutils literal notranslate"><span class="pre">itertext()</span></code></a> yields all chunks of

  2017. text that are descendants of the element.  For example:</p>

  2018. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">t</span> <span class="o">=</span> <span class="n">ET</span><span class="o">.</span><span class="n">XML</span><span class="p">(</span><span class="s2">&quot;&quot;&quot;&lt;list&gt;</span>

  2019. <span class="s2">  &lt;item&gt;1&lt;/item&gt; &lt;item&gt;2&lt;/item&gt;  &lt;item&gt;3&lt;/item&gt;</span>

  2020. <span class="s2">&lt;/list&gt;&quot;&quot;&quot;</span><span class="p">)</span>

  2021. 

  2022. <span class="c1"># Outputs [&#39;\n  &#39;, &#39;1&#39;, &#39; &#39;, &#39;2&#39;, &#39;  &#39;, &#39;3&#39;, &#39;\n&#39;]</span>

  2023. <span class="nb">print</span> <span class="nb">list</span><span class="p">(</span><span class="n">t</span><span class="o">.</span><span class="n">itertext</span><span class="p">())</span>

  2024. </pre></div>

  2025. </div>

  2026. </li>

  2027. <li><p>Deprecated: using an element as a Boolean (i.e., <code class="docutils literal notranslate"><span class="pre">if</span> <span class="pre">elem:</span></code>) would

  2028. return true if the element had any children, or false if there were

  2029. no children.  This behaviour is confusing – <code class="docutils literal notranslate"><span class="pre">None</span></code> is false, but

  2030. so is a childless element? – so it will now trigger a

  2031. <a class="reference internal" href="../library/exceptions.html#FutureWarning" title="FutureWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">FutureWarning</span></code></a>.  In your code, you should be explicit: write

  2032. <code class="docutils literal notranslate"><span class="pre">len(elem)</span> <span class="pre">!=</span> <span class="pre">0</span></code> if you’re interested in the number of children,

  2033. or <code class="docutils literal notranslate"><span class="pre">elem</span> <span class="pre">is</span> <span class="pre">not</span> <span class="pre">None</span></code>.</p></li>

  2034. </ul>

  2035. <p>Fredrik Lundh develops ElementTree and produced the 1.3 version;

  2036. you can read his article describing 1.3 at

  2037. <a class="reference external" href="https://web.archive.org/web/20200703234532/http://effbot.org/zone/elementtree-13-intro.htm">https://web.archive.org/web/20200703234532/http://effbot.org/zone/elementtree-13-intro.htm</a>.

  2038. Florent Xicluna updated the version included with

  2039. Python, after discussions on python-dev and in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6472">bpo-6472</a>.)</p>

  2040. </section>

  2041. </section>

  2042. <section id="build-and-c-api-changes">

  2043. <h2>Build and C API Changes<a class="headerlink" href="#build-and-c-api-changes" title="Link to this heading">¶</a></h2>

  2044. <p>Changes to Python’s build process and to the C API include:</p>

  2045. <ul>

  2046. <li><p>The latest release of the GNU Debugger, GDB 7, can be <a class="reference external" href="https://web.archive.org/web/20110715084810/http://sourceware.org/gdb/current/onlinedocs/gdb/Python.html">scripted

  2047. using Python</a>.

  2048. When you begin debugging an executable program P, GDB will look for

  2049. a file named <code class="docutils literal notranslate"><span class="pre">P-gdb.py</span></code> and automatically read it.  Dave Malcolm

  2050. contributed a <code class="file docutils literal notranslate"><span class="pre">python-gdb.py</span></code> that adds a number of

  2051. commands useful when debugging Python itself.  For example,

  2052. <code class="docutils literal notranslate"><span class="pre">py-up</span></code> and <code class="docutils literal notranslate"><span class="pre">py-down</span></code> go up or down one Python stack frame,

  2053. which usually corresponds to several C stack frames.  <code class="docutils literal notranslate"><span class="pre">py-print</span></code>

  2054. prints the value of a Python variable, and <code class="docutils literal notranslate"><span class="pre">py-bt</span></code> prints the

  2055. Python stack trace.  (Added as a result of <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8032">bpo-8032</a>.)</p></li>

  2056. <li><p>If you use the <code class="file docutils literal notranslate"><span class="pre">.gdbinit</span></code> file provided with Python,

  2057. the “pyo” macro in the 2.7 version now works correctly when the thread being

  2058. debugged doesn’t hold the GIL; the macro now acquires it before printing.

  2059. (Contributed by Victor Stinner; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3632">bpo-3632</a>.)</p></li>

  2060. <li><p><a class="reference internal" href="../c-api/init.html#c.Py_AddPendingCall" title="Py_AddPendingCall"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_AddPendingCall()</span></code></a> is now thread-safe, letting any

  2061. worker thread submit notifications to the main Python thread.  This

  2062. is particularly useful for asynchronous IO operations.

  2063. (Contributed by Kristján Valur Jónsson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4293">bpo-4293</a>.)</p></li>

  2064. <li><p>New function: <a class="reference internal" href="../c-api/code.html#c.PyCode_NewEmpty" title="PyCode_NewEmpty"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyCode_NewEmpty()</span></code></a> creates an empty code object;

  2065. only the filename, function name, and first line number are required.

  2066. This is useful for extension modules that are attempting to

  2067. construct a more useful traceback stack.  Previously such

  2068. extensions needed to call <code class="xref c c-func docutils literal notranslate"><span class="pre">PyCode_New()</span></code>, which had many

  2069. more arguments.  (Added by Jeffrey Yasskin.)</p></li>

  2070. <li><p>New function: <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_NewExceptionWithDoc" title="PyErr_NewExceptionWithDoc"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyErr_NewExceptionWithDoc()</span></code></a> creates a new

  2071. exception class, just as the existing <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_NewException" title="PyErr_NewException"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyErr_NewException()</span></code></a> does,

  2072. but takes an extra <code class="docutils literal notranslate"><span class="pre">char</span> <span class="pre">*</span></code> argument containing the docstring for the

  2073. new exception class.  (Added by ‘lekma’ on the Python bug tracker;

  2074. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7033">bpo-7033</a>.)</p></li>

  2075. <li><p>New function: <a class="reference internal" href="../c-api/frame.html#c.PyFrame_GetLineNumber" title="PyFrame_GetLineNumber"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyFrame_GetLineNumber()</span></code></a> takes a frame object

  2076. and returns the line number that the frame is currently executing.

  2077. Previously code would need to get the index of the bytecode

  2078. instruction currently executing, and then look up the line number

  2079. corresponding to that address.  (Added by Jeffrey Yasskin.)</p></li>

  2080. <li><p>New functions: <a class="reference internal" href="../c-api/long.html#c.PyLong_AsLongAndOverflow" title="PyLong_AsLongAndOverflow"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyLong_AsLongAndOverflow()</span></code></a> and

  2081. <a class="reference internal" href="../c-api/long.html#c.PyLong_AsLongLongAndOverflow" title="PyLong_AsLongLongAndOverflow"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyLong_AsLongLongAndOverflow()</span></code></a>  approximates a Python long

  2082. integer as a C <span class="c-expr sig sig-inline c"><span class="kt">long</span></span> or <span class="c-expr sig sig-inline c"><span class="kt">long</span><span class="w"> </span><span class="kt">long</span></span>.

  2083. If the number is too large to fit into

  2084. the output type, an <em>overflow</em> flag is set and returned to the caller.

  2085. (Contributed by Case Van Horsen; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7528">bpo-7528</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7767">bpo-7767</a>.)</p></li>

  2086. <li><p>New function: stemming from the rewrite of string-to-float conversion,

  2087. a new <a class="reference internal" href="../c-api/conversion.html#c.PyOS_string_to_double" title="PyOS_string_to_double"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyOS_string_to_double()</span></code></a> function was added.  The old

  2088. <code class="xref c c-func docutils literal notranslate"><span class="pre">PyOS_ascii_strtod()</span></code> and <code class="xref c c-func docutils literal notranslate"><span class="pre">PyOS_ascii_atof()</span></code> functions

  2089. are now deprecated.</p></li>

  2090. <li><p>New function: <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgvEx" title="PySys_SetArgvEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_SetArgvEx()</span></code></a> sets the value of

  2091. <code class="docutils literal notranslate"><span class="pre">sys.argv</span></code> and can optionally update <code class="docutils literal notranslate"><span class="pre">sys.path</span></code> to include the

  2092. directory containing the script named by <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> depending

  2093. on the value of an <em>updatepath</em> parameter.</p>

  2094. <p>This function was added to close a security hole for applications

  2095. that embed Python.  The old function, <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgv" title="PySys_SetArgv"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_SetArgv()</span></code></a>, would

  2096. always update <code class="docutils literal notranslate"><span class="pre">sys.path</span></code>, and sometimes it would add the current

  2097. directory.  This meant that, if you ran an application embedding

  2098. Python in a directory controlled by someone else, attackers could

  2099. put a Trojan-horse module in the directory (say, a file named

  2100. <code class="file docutils literal notranslate"><span class="pre">os.py</span></code>) that your application would then import and run.</p>

  2101. <p>If you maintain a C/C++ application that embeds Python, check

  2102. whether you’re calling <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgv" title="PySys_SetArgv"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_SetArgv()</span></code></a> and carefully consider

  2103. whether the application should be using <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgvEx" title="PySys_SetArgvEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_SetArgvEx()</span></code></a>

  2104. with <em>updatepath</em> set to false.</p>

  2105. <p>Security issue reported as <a class="reference external" href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983">CVE-2008-5983</a>;

  2106. discussed in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5753">bpo-5753</a>, and fixed by Antoine Pitrou.</p>

  2107. </li>

  2108. <li><p>New macros: the Python header files now define the following macros:

  2109. <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_ISALNUM</span></code>,

  2110. <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_ISALPHA</span></code>,

  2111. <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_ISDIGIT</span></code>,

  2112. <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_ISLOWER</span></code>,

  2113. <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_ISSPACE</span></code>,

  2114. <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_ISUPPER</span></code>,

  2115. <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_ISXDIGIT</span></code>,

  2116. <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_TOLOWER</span></code>, and <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_TOUPPER</span></code>.

  2117. All of these functions are analogous to the C

  2118. standard macros for classifying characters, but ignore the current

  2119. locale setting, because in

  2120. several places Python needs to analyze characters in a

  2121. locale-independent way.  (Added by Eric Smith;

  2122. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5793">bpo-5793</a>.)</p>

  2123. </li>

  2124. <li><p>Removed function: <code class="xref c c-func docutils literal notranslate"><span class="pre">PyEval_CallObject()</span></code> is now only available

  2125. as a macro.  A function version was being kept around to preserve

  2126. ABI linking compatibility, but that was in 1997; it can certainly be

  2127. deleted by now.  (Removed by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8276">bpo-8276</a>.)</p></li>

  2128. <li><p>New format codes: the <code class="xref c c-func docutils literal notranslate"><span class="pre">PyString_FromFormat()</span></code>,

  2129. <code class="xref c c-func docutils literal notranslate"><span class="pre">PyString_FromFormatV()</span></code>, and <a class="reference internal" href="../c-api/exceptions.html#c.PyErr_Format" title="PyErr_Format"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyErr_Format()</span></code></a> functions now

  2130. accept <code class="docutils literal notranslate"><span class="pre">%lld</span></code> and <code class="docutils literal notranslate"><span class="pre">%llu</span></code> format codes for displaying

  2131. C’s <span class="c-expr sig sig-inline c"><span class="kt">long</span><span class="w"> </span><span class="kt">long</span></span> types.

  2132. (Contributed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7228">bpo-7228</a>.)</p></li>

  2133. <li><p>The complicated interaction between threads and process forking has

  2134. been changed.  Previously, the child process created by

  2135. <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fork()</span></code></a> might fail because the child is created with only a

  2136. single thread running, the thread performing the <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fork()</span></code></a>.

  2137. If other threads were holding a lock, such as Python’s import lock,

  2138. when the fork was performed, the lock would still be marked as

  2139. “held” in the new process.  But in the child process nothing would

  2140. ever release the lock, since the other threads weren’t replicated,

  2141. and the child process would no longer be able to perform imports.</p>

  2142. <p>Python 2.7 acquires the import lock before performing an

  2143. <a class="reference internal" href="../library/os.html#os.fork" title="os.fork"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fork()</span></code></a>, and will also clean up any locks created using the

  2144. <a class="reference internal" href="../library/threading.html#module-threading" title="threading: Thread-based parallelism."><code class="xref py py-mod docutils literal notranslate"><span class="pre">threading</span></code></a> module.  C extension modules that have internal

  2145. locks, or that call <code class="xref c c-func docutils literal notranslate"><span class="pre">fork()</span></code> themselves, will not benefit

  2146. from this clean-up.</p>

  2147. <p>(Fixed by Thomas Wouters; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1590864">bpo-1590864</a>.)</p>

  2148. </li>

  2149. <li><p>The <a class="reference internal" href="../c-api/init.html#c.Py_Finalize" title="Py_Finalize"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_Finalize()</span></code></a> function now calls the internal

  2150. <code class="xref py py-func docutils literal notranslate"><span class="pre">threading._shutdown()</span></code> function; this prevents some exceptions from

  2151. being raised when an interpreter shuts down.

  2152. (Patch by Adam Olsen; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1722344">bpo-1722344</a>.)</p></li>

  2153. <li><p>When using the <a class="reference internal" href="../c-api/structures.html#c.PyMemberDef" title="PyMemberDef"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyMemberDef</span></code></a> structure to define attributes

  2154. of a type, Python will no longer let you try to delete or set a

  2155. <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_STRING_INPLACE</span></code> attribute.</p>

  2156. </li>

  2157. <li><p>Global symbols defined by the <a class="reference internal" href="../library/ctypes.html#module-ctypes" title="ctypes: A foreign function library for Python."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ctypes</span></code></a> module are now prefixed

  2158. with <code class="docutils literal notranslate"><span class="pre">Py</span></code>, or with <code class="docutils literal notranslate"><span class="pre">_ctypes</span></code>.  (Implemented by Thomas

  2159. Heller; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3102">bpo-3102</a>.)</p></li>

  2160. <li><p>New configure option: the <code class="xref std std-option docutils literal notranslate"><span class="pre">--with-system-expat</span></code> switch allows

  2161. building the <a class="reference internal" href="../library/pyexpat.html#module-xml.parsers.expat" title="xml.parsers.expat: An interface to the Expat non-validating XML parser."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pyexpat</span></code></a> module to use the system Expat library.

  2162. (Contributed by Arfrever Frehtes Taifersar Arahesis; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7609">bpo-7609</a>.)</p></li>

  2163. <li><p>New configure option: the

  2164. <code class="xref std std-option docutils literal notranslate"><span class="pre">--with-valgrind</span></code> option will now disable the pymalloc

  2165. allocator, which is difficult for the Valgrind memory-error detector

  2166. to analyze correctly.

  2167. Valgrind will therefore be better at detecting memory leaks and

  2168. overruns. (Contributed by James Henstridge; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2422">bpo-2422</a>.)</p></li>

  2169. <li><p>New configure option: you can now supply an empty string to

  2170. <code class="xref std std-option docutils literal notranslate"><span class="pre">--with-dbmliborder=</span></code> in order to disable all of the various

  2171. DBM modules.  (Added by Arfrever Frehtes Taifersar Arahesis;

  2172. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6491">bpo-6491</a>.)</p></li>

  2173. <li><p>The <strong class="program">configure</strong> script now checks for floating-point rounding bugs

  2174. on certain 32-bit Intel chips and defines a <code class="xref c c-macro docutils literal notranslate"><span class="pre">X87_DOUBLE_ROUNDING</span></code>

  2175. preprocessor definition.  No code currently uses this definition,

  2176. but it’s available if anyone wishes to use it.

  2177. (Added by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2937">bpo-2937</a>.)</p>

  2178. <p><strong class="program">configure</strong> also now sets a <span class="target" id="index-11"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">LDCXXSHARED</span></code> Makefile

  2179. variable for supporting C++ linking.  (Contributed by Arfrever

  2180. Frehtes Taifersar Arahesis; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1222585">bpo-1222585</a>.)</p>

  2181. </li>

  2182. <li><p>The build process now creates the necessary files for pkg-config

  2183. support.  (Contributed by Clinton Roy; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3585">bpo-3585</a>.)</p></li>

  2184. <li><p>The build process now supports Subversion 1.7.  (Contributed by

  2185. Arfrever Frehtes Taifersar Arahesis; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6094">bpo-6094</a>.)</p></li>

  2186. </ul>

  2187. <section id="capsules">

  2188. <span id="whatsnew27-capsules"></span><h3>Capsules<a class="headerlink" href="#capsules" title="Link to this heading">¶</a></h3>

  2189. <p>Python 3.1 adds a new C datatype, <a class="reference internal" href="../c-api/capsule.html#c.PyCapsule" title="PyCapsule"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyCapsule</span></code></a>, for providing a

  2190. C API to an extension module.  A capsule is essentially the holder of

  2191. a C <code class="docutils literal notranslate"><span class="pre">void</span> <span class="pre">*</span></code> pointer, and is made available as a module attribute; for

  2192. example, the <a class="reference internal" href="../library/socket.html#module-socket" title="socket: Low-level networking interface."><code class="xref py py-mod docutils literal notranslate"><span class="pre">socket</span></code></a> module’s API is exposed as <code class="docutils literal notranslate"><span class="pre">socket.CAPI</span></code>,

  2193. and <a class="reference internal" href="../library/unicodedata.html#module-unicodedata" title="unicodedata: Access the Unicode Database."><code class="xref py py-mod docutils literal notranslate"><span class="pre">unicodedata</span></code></a> exposes <code class="docutils literal notranslate"><span class="pre">ucnhash_CAPI</span></code>.  Other extensions

  2194. can import the module, access its dictionary to get the capsule

  2195. object, and then get the <code class="docutils literal notranslate"><span class="pre">void</span> <span class="pre">*</span></code> pointer, which will usually point

  2196. to an array of pointers to the module’s various API functions.</p>

  2197. <p>There is an existing data type already used for this,

  2198. <code class="xref c c-type docutils literal notranslate"><span class="pre">PyCObject</span></code>, but it doesn’t provide type safety.  Evil code

  2199. written in pure Python could cause a segmentation fault by taking a

  2200. <code class="xref c c-type docutils literal notranslate"><span class="pre">PyCObject</span></code> from module A and somehow substituting it for the

  2201. <code class="xref c c-type docutils literal notranslate"><span class="pre">PyCObject</span></code> in module B.   Capsules know their own name,

  2202. and getting the pointer requires providing the name:</p>

  2203. <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">vtable</span><span class="p">;</span>

  2204. 

  2205. <span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">PyCapsule_IsValid</span><span class="p">(</span><span class="n">capsule</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;mymodule.CAPI&quot;</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>

  2206. <span class="w">        </span><span class="n">PyErr_SetString</span><span class="p">(</span><span class="n">PyExc_ValueError</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;argument type invalid&quot;</span><span class="p">);</span>

  2207. <span class="w">        </span><span class="k">return</span><span class="w"> </span><span class="nb">NULL</span><span class="p">;</span>

  2208. <span class="p">}</span>

  2209. 

  2210. <span class="n">vtable</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PyCapsule_GetPointer</span><span class="p">(</span><span class="n">capsule</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;mymodule.CAPI&quot;</span><span class="p">);</span>

  2211. </pre></div>

  2212. </div>

  2213. <p>You are assured that <code class="docutils literal notranslate"><span class="pre">vtable</span></code> points to whatever you’re expecting.

  2214. If a different capsule was passed in, <a class="reference internal" href="../c-api/capsule.html#c.PyCapsule_IsValid" title="PyCapsule_IsValid"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyCapsule_IsValid()</span></code></a> would

  2215. detect the mismatched name and return false.  Refer to

  2216. <a class="reference internal" href="../extending/extending.html#using-capsules"><span class="std std-ref">Providing a C API for an Extension Module</span></a> for more information on using these objects.</p>

  2217. <p>Python 2.7 now uses capsules internally to provide various

  2218. extension-module APIs, but the <code class="xref c c-func docutils literal notranslate"><span class="pre">PyCObject_AsVoidPtr()</span></code> was

  2219. modified to handle capsules, preserving compile-time compatibility

  2220. with the <code class="xref c c-type docutils literal notranslate"><span class="pre">PyCObject</span></code> interface.  Use of

  2221. <code class="xref c c-func docutils literal notranslate"><span class="pre">PyCObject_AsVoidPtr()</span></code> will signal a

  2222. <a class="reference internal" href="../library/exceptions.html#PendingDeprecationWarning" title="PendingDeprecationWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">PendingDeprecationWarning</span></code></a>, which is silent by default.</p>

  2223. <p>Implemented in Python 3.1 and backported to 2.7 by Larry Hastings;

  2224. discussed in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5630">bpo-5630</a>.</p>

  2225. </section>

  2226. <section id="port-specific-changes-windows">

  2227. <h3>Port-Specific Changes: Windows<a class="headerlink" href="#port-specific-changes-windows" title="Link to this heading">¶</a></h3>

  2228. <ul class="simple">

  2229. <li><p>The <a class="reference internal" href="../library/msvcrt.html#module-msvcrt" title="msvcrt: Miscellaneous useful routines from the MS VC++ runtime. (Windows)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">msvcrt</span></code></a> module now contains some constants from

  2230. the <code class="file docutils literal notranslate"><span class="pre">crtassem.h</span></code> header file:

  2231. <a class="reference internal" href="../library/msvcrt.html#msvcrt.CRT_ASSEMBLY_VERSION" title="msvcrt.CRT_ASSEMBLY_VERSION"><code class="xref py py-data docutils literal notranslate"><span class="pre">CRT_ASSEMBLY_VERSION</span></code></a>,

  2232. <a class="reference internal" href="../library/msvcrt.html#msvcrt.VC_ASSEMBLY_PUBLICKEYTOKEN" title="msvcrt.VC_ASSEMBLY_PUBLICKEYTOKEN"><code class="xref py py-data docutils literal notranslate"><span class="pre">VC_ASSEMBLY_PUBLICKEYTOKEN</span></code></a>,

  2233. and <a class="reference internal" href="../library/msvcrt.html#msvcrt.LIBRARIES_ASSEMBLY_NAME_PREFIX" title="msvcrt.LIBRARIES_ASSEMBLY_NAME_PREFIX"><code class="xref py py-data docutils literal notranslate"><span class="pre">LIBRARIES_ASSEMBLY_NAME_PREFIX</span></code></a>.

  2234. (Contributed by David Cournapeau; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4365">bpo-4365</a>.)</p></li>

  2235. <li><p>The <a class="reference internal" href="../library/winreg.html#module-winreg" title="winreg: Routines and objects for manipulating the Windows registry. (Windows)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">_winreg</span></code></a> module for accessing the registry now implements

  2236. the <a class="reference internal" href="../library/winreg.html#winreg.CreateKeyEx" title="winreg.CreateKeyEx"><code class="xref py py-func docutils literal notranslate"><span class="pre">CreateKeyEx()</span></code></a> and <a class="reference internal" href="../library/winreg.html#winreg.DeleteKeyEx" title="winreg.DeleteKeyEx"><code class="xref py py-func docutils literal notranslate"><span class="pre">DeleteKeyEx()</span></code></a>

  2237. functions, extended versions of previously supported functions that

  2238. take several extra arguments.  The <a class="reference internal" href="../library/winreg.html#winreg.DisableReflectionKey" title="winreg.DisableReflectionKey"><code class="xref py py-func docutils literal notranslate"><span class="pre">DisableReflectionKey()</span></code></a>,

  2239. <a class="reference internal" href="../library/winreg.html#winreg.EnableReflectionKey" title="winreg.EnableReflectionKey"><code class="xref py py-func docutils literal notranslate"><span class="pre">EnableReflectionKey()</span></code></a>, and <a class="reference internal" href="../library/winreg.html#winreg.QueryReflectionKey" title="winreg.QueryReflectionKey"><code class="xref py py-func docutils literal notranslate"><span class="pre">QueryReflectionKey()</span></code></a>

  2240. were also tested and documented.

  2241. (Implemented by Brian Curtin: <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7347">bpo-7347</a>.)</p></li>

  2242. <li><p>The new <code class="xref c c-func docutils literal notranslate"><span class="pre">_beginthreadex()</span></code> API is used to start threads, and

  2243. the native thread-local storage functions are now used.

  2244. (Contributed by Kristján Valur Jónsson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3582">bpo-3582</a>.)</p></li>

  2245. <li><p>The <a class="reference internal" href="../library/os.html#os.kill" title="os.kill"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.kill()</span></code></a> function now works on Windows.  The signal value

  2246. can be the constants <a class="reference internal" href="../library/signal.html#signal.CTRL_C_EVENT" title="signal.CTRL_C_EVENT"><code class="xref py py-const docutils literal notranslate"><span class="pre">CTRL_C_EVENT</span></code></a>,

  2247. <a class="reference internal" href="../library/signal.html#signal.CTRL_BREAK_EVENT" title="signal.CTRL_BREAK_EVENT"><code class="xref py py-const docutils literal notranslate"><span class="pre">CTRL_BREAK_EVENT</span></code></a>, or any integer.  The first two constants

  2248. will send <kbd class="kbd compound docutils literal notranslate"><kbd class="kbd docutils literal notranslate">Control</kbd>-<kbd class="kbd docutils literal notranslate">C</kbd></kbd> and <kbd class="kbd compound docutils literal notranslate"><kbd class="kbd docutils literal notranslate">Control</kbd>-<kbd class="kbd docutils literal notranslate">Break</kbd></kbd> keystroke events to

  2249. subprocesses; any other value will use the <code class="xref c c-func docutils literal notranslate"><span class="pre">TerminateProcess()</span></code>

  2250. API.  (Contributed by Miki Tebeka; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1220212">bpo-1220212</a>.)</p></li>

  2251. <li><p>The <a class="reference internal" href="../library/os.html#os.listdir" title="os.listdir"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.listdir()</span></code></a> function now correctly fails

  2252. for an empty path.  (Fixed by Hirokazu Yamamoto; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5913">bpo-5913</a>.)</p></li>

  2253. <li><p>The <a class="reference internal" href="../library/mimetypes.html#module-mimetypes" title="mimetypes: Mapping of filename extensions to MIME types."><code class="xref py py-mod docutils literal notranslate"><span class="pre">mimetypes</span></code></a> module will now read the MIME database from

  2254. the Windows registry when initializing.

  2255. (Patch by Gabriel Genellina; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4969">bpo-4969</a>.)</p></li>

  2256. </ul>

  2257. </section>

  2258. <section id="port-specific-changes-mac-os-x">

  2259. <h3>Port-Specific Changes: Mac OS X<a class="headerlink" href="#port-specific-changes-mac-os-x" title="Link to this heading">¶</a></h3>

  2260. <ul>

  2261. <li><p>The path <code class="docutils literal notranslate"><span class="pre">/Library/Python/2.7/site-packages</span></code> is now appended to

  2262. <code class="docutils literal notranslate"><span class="pre">sys.path</span></code>, in order to share added packages between the system

  2263. installation and a user-installed copy of the same version.

  2264. (Changed by Ronald Oussoren; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4865">bpo-4865</a>.)</p>

  2265. <div class="versionchanged">

  2266. <p><span class="versionmodified changed">Changed in version 2.7.13: </span>As of 2.7.13, this change was removed.

  2267. <code class="docutils literal notranslate"><span class="pre">/Library/Python/2.7/site-packages</span></code>, the site-packages directory

  2268. used by the Apple-supplied system Python 2.7 is no longer appended to

  2269. <code class="docutils literal notranslate"><span class="pre">sys.path</span></code> for user-installed Pythons such as from the python.org

  2270. installers.  As of macOS 10.12, Apple changed how the system

  2271. site-packages directory is configured, which could cause installation

  2272. of pip components, like setuptools, to fail.  Packages installed for

  2273. the system Python will no longer be shared with user-installed

  2274. Pythons. (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=28440">bpo-28440</a>)</p>

  2275. </div>

  2276. </li>

  2277. </ul>

  2278. </section>

  2279. <section id="port-specific-changes-freebsd">

  2280. <h3>Port-Specific Changes: FreeBSD<a class="headerlink" href="#port-specific-changes-freebsd" title="Link to this heading">¶</a></h3>

  2281. <ul class="simple">

  2282. <li><p>FreeBSD 7.1’s <code class="xref py py-const docutils literal notranslate"><span class="pre">SO_SETFIB</span></code> constant, used with the <a class="reference internal" href="../library/socket.html#socket.socket" title="socket.socket"><code class="xref py py-func docutils literal notranslate"><span class="pre">socket()</span></code></a> methods

  2283. <a class="reference internal" href="../library/socket.html#socket.socket.getsockopt" title="socket.socket.getsockopt"><code class="xref py py-func docutils literal notranslate"><span class="pre">getsockopt()</span></code></a>/<a class="reference internal" href="../library/socket.html#socket.socket.setsockopt" title="socket.socket.setsockopt"><code class="xref py py-func docutils literal notranslate"><span class="pre">setsockopt()</span></code></a> to select an

  2284. alternate routing table, is now available in the <a class="reference internal" href="../library/socket.html#module-socket" title="socket: Low-level networking interface."><code class="xref py py-mod docutils literal notranslate"><span class="pre">socket</span></code></a>

  2285. module.  (Added by Kyle VanderBeek; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8235">bpo-8235</a>.)</p></li>

  2286. </ul>

  2287. </section>

  2288. </section>

  2289. <section id="other-changes-and-fixes">

  2290. <h2>Other Changes and Fixes<a class="headerlink" href="#other-changes-and-fixes" title="Link to this heading">¶</a></h2>

  2291. <ul class="simple">

  2292. <li><p>Two benchmark scripts, <code class="file docutils literal notranslate"><span class="pre">iobench</span></code> and <code class="file docutils literal notranslate"><span class="pre">ccbench</span></code>, were

  2293. added to the <code class="file docutils literal notranslate"><span class="pre">Tools</span></code> directory.  <code class="file docutils literal notranslate"><span class="pre">iobench</span></code> measures the

  2294. speed of the built-in file I/O objects returned by <a class="reference internal" href="../library/functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate"><span class="pre">open()</span></code></a>

  2295. while performing various operations, and <code class="file docutils literal notranslate"><span class="pre">ccbench</span></code> is a

  2296. concurrency benchmark that tries to measure computing throughput,

  2297. thread switching latency, and IO processing bandwidth when

  2298. performing several tasks using a varying number of threads.</p></li>

  2299. <li><p>The <code class="file docutils literal notranslate"><span class="pre">Tools/i18n/msgfmt.py</span></code> script now understands plural

  2300. forms in <code class="file docutils literal notranslate"><span class="pre">.po</span></code> files.  (Fixed by Martin von Löwis;

  2301. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5464">bpo-5464</a>.)</p></li>

  2302. <li><p>When importing a module from a <code class="file docutils literal notranslate"><span class="pre">.pyc</span></code> or <code class="file docutils literal notranslate"><span class="pre">.pyo</span></code> file

  2303. with an existing <code class="file docutils literal notranslate"><span class="pre">.py</span></code> counterpart, the <a class="reference internal" href="../reference/datamodel.html#codeobject.co_filename" title="codeobject.co_filename"><code class="xref py py-attr docutils literal notranslate"><span class="pre">co_filename</span></code></a>

  2304. attributes of the resulting code objects are overwritten when the

  2305. original filename is obsolete.  This can happen if the file has been

  2306. renamed, moved, or is accessed through different paths.  (Patch by

  2307. Ziga Seilnacht and Jean-Paul Calderone; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1180193">bpo-1180193</a>.)</p></li>

  2308. <li><p>The <code class="file docutils literal notranslate"><span class="pre">regrtest.py</span></code> script now takes a <code class="xref std std-option docutils literal notranslate"><span class="pre">--randseed=</span></code>

  2309. switch that takes an integer that will be used as the random seed

  2310. for the <code class="xref std std-option docutils literal notranslate"><span class="pre">-r</span></code> option that executes tests in random order.

  2311. The <code class="xref std std-option docutils literal notranslate"><span class="pre">-r</span></code> option also reports the seed that was used

  2312. (Added by Collin Winter.)</p></li>

  2313. <li><p>Another <code class="file docutils literal notranslate"><span class="pre">regrtest.py</span></code> switch is <code class="xref std std-option docutils literal notranslate"><span class="pre">-j</span></code>, which

  2314. takes an integer specifying how many tests run in parallel. This

  2315. allows reducing the total runtime on multi-core machines.

  2316. This option is compatible with several other options, including the

  2317. <code class="xref std std-option docutils literal notranslate"><span class="pre">-R</span></code> switch which is known to produce long runtimes.

  2318. (Added by Antoine Pitrou, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6152">bpo-6152</a>.)  This can also be used

  2319. with a new <code class="xref std std-option docutils literal notranslate"><span class="pre">-F</span></code> switch that runs selected tests in a loop

  2320. until they fail.  (Added by Antoine Pitrou; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7312">bpo-7312</a>.)</p></li>

  2321. <li><p>When executed as a script, the <code class="file docutils literal notranslate"><span class="pre">py_compile.py</span></code> module now

  2322. accepts <code class="docutils literal notranslate"><span class="pre">'-'</span></code> as an argument, which will read standard input for

  2323. the list of filenames to be compiled.  (Contributed by Piotr

  2324. Ożarowski; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8233">bpo-8233</a>.)</p></li>

  2325. </ul>

  2326. </section>

  2327. <section id="porting-to-python-2-7">

  2328. <h2>Porting to Python 2.7<a class="headerlink" href="#porting-to-python-2-7" title="Link to this heading">¶</a></h2>

  2329. <p>This section lists previously described changes and other bugfixes

  2330. that may require changes to your code:</p>

  2331. <ul class="simple">

  2332. <li><p>The <a class="reference internal" href="../library/stdtypes.html#range" title="range"><code class="xref py py-func docutils literal notranslate"><span class="pre">range()</span></code></a> function processes its arguments more

  2333. consistently; it will now call <a class="reference internal" href="../reference/datamodel.html#object.__int__" title="object.__int__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__int__()</span></code></a> on non-float,

  2334. non-integer arguments that are supplied to it.  (Fixed by Alexander

  2335. Belopolsky; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1533">bpo-1533</a>.)</p></li>

  2336. <li><p>The string <a class="reference internal" href="../library/functions.html#format" title="format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">format()</span></code></a> method changed the default precision used

  2337. for floating-point and complex numbers from 6 decimal

  2338. places to 12, which matches the precision used by <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a>.

  2339. (Changed by Eric Smith; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5920">bpo-5920</a>.)</p></li>

  2340. <li><p>Because of an optimization for the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement, the special

  2341. methods <a class="reference internal" href="../reference/datamodel.html#object.__enter__" title="object.__enter__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__enter__()</span></code></a> and <a class="reference internal" href="../reference/datamodel.html#object.__exit__" title="object.__exit__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__exit__()</span></code></a> must belong to the object’s

  2342. type, and cannot be directly attached to the object’s instance.  This

  2343. affects new-style classes (derived from <a class="reference internal" href="../library/functions.html#object" title="object"><code class="xref py py-class docutils literal notranslate"><span class="pre">object</span></code></a>) and C extension

  2344. types.  (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6101">bpo-6101</a>.)</p></li>

  2345. <li><p>Due to a bug in Python 2.6, the <em>exc_value</em> parameter to

  2346. <a class="reference internal" href="../reference/datamodel.html#object.__exit__" title="object.__exit__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__exit__()</span></code></a> methods was often the string representation of the

  2347. exception, not an instance.  This was fixed in 2.7, so <em>exc_value</em>

  2348. will be an instance as expected.  (Fixed by Florent Xicluna;

  2349. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7853">bpo-7853</a>.)</p></li>

  2350. <li><p>When a restricted set of attributes were set using <code class="docutils literal notranslate"><span class="pre">__slots__</span></code>,

  2351. deleting an unset attribute would not raise <a class="reference internal" href="../library/exceptions.html#AttributeError" title="AttributeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">AttributeError</span></code></a>

  2352. as you would expect.  Fixed by Benjamin Peterson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7604">bpo-7604</a>.)</p></li>

  2353. </ul>

  2354. <p>In the standard library:</p>

  2355. <ul>

  2356. <li><p>Operations with <a class="reference internal" href="../library/datetime.html#datetime.datetime" title="datetime.datetime"><code class="xref py py-class docutils literal notranslate"><span class="pre">datetime</span></code></a> instances that resulted in a year

  2357. falling outside the supported range didn’t always raise

  2358. <a class="reference internal" href="../library/exceptions.html#OverflowError" title="OverflowError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OverflowError</span></code></a>.  Such errors are now checked more carefully

  2359. and will now raise the exception. (Reported by Mark Leander, patch

  2360. by Anand B. Pillai and Alexander Belopolsky; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7150">bpo-7150</a>.)</p></li>

  2361. <li><p>When using <a class="reference internal" href="../library/decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">Decimal</span></code></a> instances with a string’s

  2362. <a class="reference internal" href="../library/functions.html#format" title="format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">format()</span></code></a> method, the default alignment was previously

  2363. left-alignment.  This has been changed to right-alignment, which might

  2364. change the output of your programs.

  2365. (Changed by Mark Dickinson; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6857">bpo-6857</a>.)</p>

  2366. <p>Comparisons involving a signaling NaN value (or <code class="docutils literal notranslate"><span class="pre">sNAN</span></code>) now signal

  2367. <a class="reference internal" href="../library/decimal.html#decimal.InvalidOperation" title="decimal.InvalidOperation"><code class="xref py py-const docutils literal notranslate"><span class="pre">InvalidOperation</span></code></a> instead of silently returning a true or

  2368. false value depending on the comparison operator.  Quiet NaN values

  2369. (or <code class="docutils literal notranslate"><span class="pre">NaN</span></code>) are now hashable.  (Fixed by Mark Dickinson;

  2370. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7279">bpo-7279</a>.)</p>

  2371. </li>

  2372. <li><p>The <a class="reference internal" href="../library/xml.etree.elementtree.html#module-xml.etree.ElementTree" title="xml.etree.ElementTree: Implementation of the ElementTree API."><code class="xref py py-mod docutils literal notranslate"><span class="pre">xml.etree.ElementTree</span></code></a> library no longer escapes

  2373. ampersands and angle brackets when outputting an XML processing

  2374. instruction (which looks like <code class="docutils literal notranslate"><span class="pre">&lt;?xml-stylesheet</span> <span class="pre">href=&quot;#style1&quot;?&gt;</span></code>)

  2375. or comment (which looks like <code class="docutils literal notranslate"><span class="pre">&lt;!--</span> <span class="pre">comment</span> <span class="pre">--&gt;</span></code>).

  2376. (Patch by Neil Muller; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2746">bpo-2746</a>.)</p></li>

  2377. <li><p>The <code class="xref py py-meth docutils literal notranslate"><span class="pre">readline()</span></code> method of <a class="reference internal" href="../library/io.html#io.StringIO" title="io.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">StringIO</span></code></a> objects now does

  2378. nothing when a negative length is requested, as other file-like

  2379. objects do.  (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7348">bpo-7348</a>).</p></li>

  2380. <li><p>The <a class="reference internal" href="../library/syslog.html#module-syslog" title="syslog: An interface to the Unix syslog library routines. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">syslog</span></code></a> module will now use the value of <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> as the

  2381. identifier instead of the previous default value of <code class="docutils literal notranslate"><span class="pre">'python'</span></code>.

  2382. (Changed by Sean Reifschneider; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8451">bpo-8451</a>.)</p></li>

  2383. <li><p>The <a class="reference internal" href="../library/tarfile.html#module-tarfile" title="tarfile: Read and write tar-format archive files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">tarfile</span></code></a> module’s default error handling has changed, to

  2384. no longer suppress fatal errors.  The default error level was previously 0,

  2385. which meant that errors would only result in a message being written to the

  2386. debug log, but because the debug log is not activated by default,

  2387. these errors go unnoticed.  The default error level is now 1,

  2388. which raises an exception if there’s an error.

  2389. (Changed by Lars Gustäbel; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7357">bpo-7357</a>.)</p></li>

  2390. <li><p>The <a class="reference internal" href="../library/urllib.parse.html#module-urllib.parse" title="urllib.parse: Parse URLs into or assemble them from components."><code class="xref py py-mod docutils literal notranslate"><span class="pre">urlparse</span></code></a> module’s <a class="reference internal" href="../library/urllib.parse.html#urllib.parse.urlsplit" title="urllib.parse.urlsplit"><code class="xref py py-func docutils literal notranslate"><span class="pre">urlsplit()</span></code></a> now handles

  2391. unknown URL schemes in a fashion compliant with <span class="target" id="index-12"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc3986.html"><strong>RFC 3986</strong></a>: if the

  2392. URL is of the form <code class="docutils literal notranslate"><span class="pre">&quot;&lt;something&gt;://...&quot;</span></code>, the text before the

  2393. <code class="docutils literal notranslate"><span class="pre">://</span></code> is treated as the scheme, even if it’s a made-up scheme that

  2394. the module doesn’t know about.  This change may break code that

  2395. worked around the old behaviour.  For example, Python 2.6.4 or 2.5

  2396. will return the following:</p>

  2397. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">urlparse</span>

  2398. <span class="gp">&gt;&gt;&gt; </span><span class="n">urlparse</span><span class="o">.</span><span class="n">urlsplit</span><span class="p">(</span><span class="s1">&#39;invented://host/filename?query&#39;</span><span class="p">)</span>

  2399. <span class="go">(&#39;invented&#39;, &#39;&#39;, &#39;//host/filename?query&#39;, &#39;&#39;, &#39;&#39;)</span>

  2400. </pre></div>

  2401. </div>

  2402. <p>Python 2.7 (and Python 2.6.5) will return:</p>

  2403. <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">urlparse</span>

  2404. <span class="gp">&gt;&gt;&gt; </span><span class="n">urlparse</span><span class="o">.</span><span class="n">urlsplit</span><span class="p">(</span><span class="s1">&#39;invented://host/filename?query&#39;</span><span class="p">)</span>

  2405. <span class="go">(&#39;invented&#39;, &#39;host&#39;, &#39;/filename?query&#39;, &#39;&#39;, &#39;&#39;)</span>

  2406. </pre></div>

  2407. </div>

  2408. <p>(Python 2.7 actually produces slightly different output, since it

  2409. returns a named tuple instead of a standard tuple.)</p>

  2410. </li>

  2411. </ul>

  2412. <p>For C extensions:</p>

  2413. <ul class="simple">

  2414. <li><p>C extensions that use integer format codes with the <code class="docutils literal notranslate"><span class="pre">PyArg_Parse*</span></code>

  2415. family of functions will now raise a <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> exception

  2416. instead of triggering a <a class="reference internal" href="../library/exceptions.html#DeprecationWarning" title="DeprecationWarning"><code class="xref py py-exc docutils literal notranslate"><span class="pre">DeprecationWarning</span></code></a> (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5080">bpo-5080</a>).</p></li>

  2417. <li><p>Use the new <a class="reference internal" href="../c-api/conversion.html#c.PyOS_string_to_double" title="PyOS_string_to_double"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyOS_string_to_double()</span></code></a> function instead of the old

  2418. <code class="xref c c-func docutils literal notranslate"><span class="pre">PyOS_ascii_strtod()</span></code> and <code class="xref c c-func docutils literal notranslate"><span class="pre">PyOS_ascii_atof()</span></code> functions,

  2419. which are now deprecated.</p></li>

  2420. </ul>

  2421. <p>For applications that embed Python:</p>

  2422. <ul class="simple">

  2423. <li><p>The <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgvEx" title="PySys_SetArgvEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_SetArgvEx()</span></code></a> function was added, letting

  2424. applications close a security hole when the existing

  2425. <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgv" title="PySys_SetArgv"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_SetArgv()</span></code></a> function was used.  Check whether you’re

  2426. calling <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgv" title="PySys_SetArgv"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_SetArgv()</span></code></a> and carefully consider whether the

  2427. application should be using <a class="reference internal" href="../c-api/init.html#c.PySys_SetArgvEx" title="PySys_SetArgvEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySys_SetArgvEx()</span></code></a> with

  2428. <em>updatepath</em> set to false.</p></li>

  2429. </ul>

  2430. </section>

  2431. <section id="new-features-added-to-python-2-7-maintenance-releases">

  2432. <span id="py27-maintenance-enhancements"></span><h2>New Features Added to Python 2.7 Maintenance Releases<a class="headerlink" href="#new-features-added-to-python-2-7-maintenance-releases" title="Link to this heading">¶</a></h2>

  2433. <p>New features may be added to Python 2.7 maintenance releases when the

  2434. situation genuinely calls for it. Any such additions must go through

  2435. the Python Enhancement Proposal process, and make a compelling case for why

  2436. they can’t be adequately addressed by either adding the new feature solely to

  2437. Python 3, or else by publishing it on the Python Package Index.</p>

  2438. <p>In addition to the specific proposals listed below, there is a general

  2439. exemption allowing new <code class="docutils literal notranslate"><span class="pre">-3</span></code> warnings to be added in any Python 2.7

  2440. maintenance release.</p>

  2441. <section id="two-new-environment-variables-for-debug-mode">

  2442. <h3>Two new environment variables for debug mode<a class="headerlink" href="#two-new-environment-variables-for-debug-mode" title="Link to this heading">¶</a></h3>

  2443. <p>In debug mode, the <code class="docutils literal notranslate"><span class="pre">[xxx</span> <span class="pre">refs]</span></code> statistic is not written by default, the

  2444. <code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONSHOWREFCOUNT</span></code> environment variable now must also be set.

  2445. (Contributed by Victor Stinner; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=31733">bpo-31733</a>.)</p>

  2446. <p>When Python is compiled with <code class="docutils literal notranslate"><span class="pre">COUNT_ALLOC</span></code> defined, allocation counts are no

  2447. longer dumped by default anymore: the <code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONSHOWALLOCCOUNT</span></code> environment

  2448. variable must now also be set. Moreover, allocation counts are now dumped into

  2449. stderr, rather than stdout. (Contributed by Victor Stinner; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=31692">bpo-31692</a>.)</p>

  2450. <div class="versionadded">

  2451. <p><span class="versionmodified added">New in version 2.7.15.</span></p>

  2452. </div>

  2453. </section>

  2454. <section id="pep-434-idle-enhancement-exception-for-all-branches">

  2455. <h3>PEP 434: IDLE Enhancement Exception for All Branches<a class="headerlink" href="#pep-434-idle-enhancement-exception-for-all-branches" title="Link to this heading">¶</a></h3>

  2456. <p><span class="target" id="index-13"></span><a class="pep reference external" href="https://peps.python.org/pep-0434/"><strong>PEP 434</strong></a> describes a general exemption for changes made to the IDLE

  2457. development environment shipped along with Python. This exemption makes it

  2458. possible for the IDLE developers to provide a more consistent user

  2459. experience across all supported versions of Python 2 and 3.</p>

  2460. <p>For details of any IDLE changes, refer to the NEWS file for the specific

  2461. release.</p>

  2462. </section>

  2463. <section id="pep-466-network-security-enhancements-for-python-2-7">

  2464. <h3>PEP 466: Network Security Enhancements for Python 2.7<a class="headerlink" href="#pep-466-network-security-enhancements-for-python-2-7" title="Link to this heading">¶</a></h3>

  2465. <p><span class="target" id="index-14"></span><a class="pep reference external" href="https://peps.python.org/pep-0466/"><strong>PEP 466</strong></a> describes a number of network security enhancement proposals

  2466. that have been approved for inclusion in Python 2.7 maintenance releases,

  2467. with the first of those changes appearing in the Python 2.7.7 release.</p>

  2468. <p><span class="target" id="index-15"></span><a class="pep reference external" href="https://peps.python.org/pep-0466/"><strong>PEP 466</strong></a> related features added in Python 2.7.7:</p>

  2469. <ul class="simple">

  2470. <li><p><a class="reference internal" href="../library/hmac.html#hmac.compare_digest" title="hmac.compare_digest"><code class="xref py py-func docutils literal notranslate"><span class="pre">hmac.compare_digest()</span></code></a> was backported from Python 3 to make a timing

  2471. attack resistant comparison operation available to Python 2 applications.

  2472. (Contributed by Alex Gaynor; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=21306">bpo-21306</a>.)</p></li>

  2473. <li><p>OpenSSL 1.0.1g was upgraded in the official Windows installers published on

  2474. python.org. (Contributed by Zachary Ware; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=21462">bpo-21462</a>.)</p></li>

  2475. </ul>

  2476. <p><span class="target" id="index-16"></span><a class="pep reference external" href="https://peps.python.org/pep-0466/"><strong>PEP 466</strong></a> related features added in Python 2.7.8:</p>

  2477. <ul class="simple">

  2478. <li><p><a class="reference internal" href="../library/hashlib.html#hashlib.pbkdf2_hmac" title="hashlib.pbkdf2_hmac"><code class="xref py py-func docutils literal notranslate"><span class="pre">hashlib.pbkdf2_hmac()</span></code></a> was backported from Python 3 to make a hashing

  2479. algorithm suitable for secure password storage broadly available to Python

  2480. 2 applications. (Contributed by Alex Gaynor; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=21304">bpo-21304</a>.)</p></li>

  2481. <li><p>OpenSSL 1.0.1h was upgraded for the official Windows installers published on

  2482. python.org. (contributed by Zachary Ware in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=21671">bpo-21671</a> for CVE-2014-0224)</p></li>

  2483. </ul>

  2484. <p><span class="target" id="index-17"></span><a class="pep reference external" href="https://peps.python.org/pep-0466/"><strong>PEP 466</strong></a> related features added in Python 2.7.9:</p>

  2485. <ul>

  2486. <li><p>Most of Python 3.4’s <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate"><span class="pre">ssl</span></code></a> module was backported. This means <a class="reference internal" href="../library/ssl.html#module-ssl" title="ssl: TLS/SSL wrapper for socket objects"><code class="xref py py-mod docutils literal notranslate"><span class="pre">ssl</span></code></a>

  2487. now supports Server Name Indication, TLS1.x settings, access to the platform

  2488. certificate store, the <a class="reference internal" href="../library/ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate"><span class="pre">SSLContext</span></code></a> class, and other

  2489. features. (Contributed by Alex Gaynor and David Reid; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=21308">bpo-21308</a>.)</p>

  2490. <p>Refer to the “Version added: 2.7.9” notes in the module documentation for

  2491. specific details.</p>

  2492. </li>

  2493. <li><p><a class="reference internal" href="../library/os.html#os.urandom" title="os.urandom"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.urandom()</span></code></a> was changed to cache a file descriptor to <code class="docutils literal notranslate"><span class="pre">/dev/urandom</span></code>

  2494. instead of reopening <code class="docutils literal notranslate"><span class="pre">/dev/urandom</span></code> on every call. (Contributed by Alex

  2495. Gaynor; <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=21305">bpo-21305</a>.)</p></li>

  2496. <li><p><a class="reference internal" href="../library/hashlib.html#hashlib.algorithms_guaranteed" title="hashlib.algorithms_guaranteed"><code class="xref py py-data docutils literal notranslate"><span class="pre">hashlib.algorithms_guaranteed</span></code></a> and

  2497. <a class="reference internal" href="../library/hashlib.html#hashlib.algorithms_available" title="hashlib.algorithms_available"><code class="xref py py-data docutils literal notranslate"><span class="pre">hashlib.algorithms_available</span></code></a> were backported from Python 3 to make

  2498. it easier for Python 2 applications to select the strongest available hash

  2499. algorithm. (Contributed by Alex Gaynor in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=21307">bpo-21307</a>)</p></li>

  2500. </ul>

  2501. </section>

  2502. <section id="pep-477-backport-ensurepip-pep-453-to-python-2-7">

  2503. <h3>PEP 477: Backport ensurepip (PEP 453) to Python 2.7<a class="headerlink" href="#pep-477-backport-ensurepip-pep-453-to-python-2-7" title="Link to this heading">¶</a></h3>

  2504. <p><span class="target" id="index-18"></span><a class="pep reference external" href="https://peps.python.org/pep-0477/"><strong>PEP 477</strong></a> approves the inclusion of the <span class="target" id="index-19"></span><a class="pep reference external" href="https://peps.python.org/pep-0453/"><strong>PEP 453</strong></a> ensurepip module and the

  2505. improved documentation that was enabled by it in the Python 2.7 maintenance

  2506. releases, appearing first in the Python 2.7.9 release.</p>

  2507. <section id="bootstrapping-pip-by-default">

  2508. <h4>Bootstrapping pip By Default<a class="headerlink" href="#bootstrapping-pip-by-default" title="Link to this heading">¶</a></h4>

  2509. <p>The new <a class="reference internal" href="../library/ensurepip.html#module-ensurepip" title="ensurepip: Bootstrapping the &quot;pip&quot; installer into an existing Python installation or virtual environment."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ensurepip</span></code></a> module (defined in <span class="target" id="index-20"></span><a class="pep reference external" href="https://peps.python.org/pep-0453/"><strong>PEP 453</strong></a>) provides a standard

  2510. cross-platform mechanism to bootstrap the pip installer into Python

  2511. installations. The version of <code class="docutils literal notranslate"><span class="pre">pip</span></code> included with Python 2.7.9 is <code class="docutils literal notranslate"><span class="pre">pip</span></code>

  2512. 1.5.6, and future 2.7.x maintenance releases will update the bundled version to

  2513. the latest version of <code class="docutils literal notranslate"><span class="pre">pip</span></code> that is available at the time of creating the

  2514. release candidate.</p>

  2515. <p>By default, the commands <code class="docutils literal notranslate"><span class="pre">pip</span></code>, <code class="docutils literal notranslate"><span class="pre">pipX</span></code> and <code class="docutils literal notranslate"><span class="pre">pipX.Y</span></code> will be installed on

  2516. all platforms (where X.Y stands for the version of the Python installation),

  2517. along with the <code class="docutils literal notranslate"><span class="pre">pip</span></code> Python package and its dependencies.</p>

  2518. <p>For CPython <a class="reference internal" href="../using/unix.html#building-python-on-unix"><span class="std std-ref">source builds on POSIX systems</span></a>,

  2519. the <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">install</span></code> and <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">altinstall</span></code> commands do not bootstrap <code class="docutils literal notranslate"><span class="pre">pip</span></code>

  2520. by default.  This behaviour can be controlled through configure options, and

  2521. overridden through Makefile options.</p>

  2522. <p>On Windows and Mac OS X, the CPython installers now default to installing

  2523. <code class="docutils literal notranslate"><span class="pre">pip</span></code> along with CPython itself (users may opt out of installing it

  2524. during the installation process). Window users will need to opt in to the

  2525. automatic <code class="docutils literal notranslate"><span class="pre">PATH</span></code> modifications to have <code class="docutils literal notranslate"><span class="pre">pip</span></code> available from the command

  2526. line by default, otherwise it can still be accessed through the Python

  2527. launcher for Windows as <code class="docutils literal notranslate"><span class="pre">py</span> <span class="pre">-m</span> <span class="pre">pip</span></code>.</p>

  2528. <p>As <a class="reference external" href="https://peps.python.org/pep-0477/#disabling-ensurepip-by-downstream-distributors">discussed in the PEP</a>, platform packagers may choose not to install

  2529. these commands by default, as long as, when invoked, they provide clear and

  2530. simple directions on how to install them on that platform (usually using

  2531. the system package manager).</p>

  2532. </section>

  2533. <section id="documentation-changes">

  2534. <h4>Documentation Changes<a class="headerlink" href="#documentation-changes" title="Link to this heading">¶</a></h4>

  2535. <p>As part of this change, the <a class="reference internal" href="../installing/index.html#installing-index"><span class="std std-ref">Installing Python Modules</span></a> and

  2536. <a class="reference internal" href="../distributing/index.html#distributing-index"><span class="std std-ref">Distributing Python Modules</span></a> sections of the documentation have been

  2537. completely redesigned as short getting started and FAQ documents. Most

  2538. packaging documentation has now been moved out to the Python Packaging

  2539. Authority maintained <a class="reference external" href="https://packaging.python.org">Python Packaging User Guide</a> and the documentation of the individual

  2540. projects.</p>

  2541. <p>However, as this migration is currently still incomplete, the legacy

  2542. versions of those guides remaining available as <a class="reference internal" href="../extending/building.html#install-index"><span class="std std-ref">Building C and C++ Extensions with setuptools</span></a>

  2543. and <a class="reference internal" href="../extending/building.html#setuptools-index"><span class="std std-ref">Building C and C++ Extensions with setuptools</span></a>.</p>

  2544. <div class="admonition seealso">

  2545. <p class="admonition-title">See also</p>

  2546. <dl class="simple">

  2547. <dt><span class="target" id="index-21"></span><a class="pep reference external" href="https://peps.python.org/pep-0453/"><strong>PEP 453</strong></a> – Explicit bootstrapping of pip in Python installations</dt><dd><p>PEP written by Donald Stufft and Nick Coghlan, implemented by

  2548. Donald Stufft, Nick Coghlan, Martin von Löwis and Ned Deily.</p>

  2549. </dd>

  2550. </dl>

  2551. </div>

  2552. </section>

  2553. </section>

  2554. <section id="pep-476-enabling-certificate-verification-by-default-for-stdlib-http-clients">

  2555. <h3>PEP 476: Enabling certificate verification by default for stdlib http clients<a class="headerlink" href="#pep-476-enabling-certificate-verification-by-default-for-stdlib-http-clients" title="Link to this heading">¶</a></h3>

  2556. <p><span class="target" id="index-22"></span><a class="pep reference external" href="https://peps.python.org/pep-0476/"><strong>PEP 476</strong></a> updated <a class="reference internal" href="../library/http.html#module-http" title="http: HTTP status codes and messages"><code class="xref py py-mod docutils literal notranslate"><span class="pre">httplib</span></code></a> and modules which use it, such as

  2557. <a class="reference internal" href="../library/urllib.request.html#module-urllib.request" title="urllib.request: Extensible library for opening URLs."><code class="xref py py-mod docutils literal notranslate"><span class="pre">urllib2</span></code></a> and <a class="reference internal" href="../library/xmlrpc.client.html#module-xmlrpc.client" title="xmlrpc.client: XML-RPC client access."><code class="xref py py-mod docutils literal notranslate"><span class="pre">xmlrpclib</span></code></a>, to now

  2558. verify that the server

  2559. presents a certificate which is signed by a Certificate Authority in the

  2560. platform trust store and whose hostname matches the hostname being requested

  2561. by default, significantly improving security for many applications. This

  2562. change was made in the Python 2.7.9 release.</p>

  2563. <p>For applications which require the old previous behavior, they can pass an

  2564. alternate context:</p>

  2565. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">urllib2</span>

  2566. <span class="kn">import</span> <span class="nn">ssl</span>

  2567. 

  2568. <span class="c1"># This disables all verification</span>

  2569. <span class="n">context</span> <span class="o">=</span> <span class="n">ssl</span><span class="o">.</span><span class="n">_create_unverified_context</span><span class="p">()</span>

  2570. 

  2571. <span class="c1"># This allows using a specific certificate for the host, which doesn&#39;t need</span>

  2572. <span class="c1"># to be in the trust store</span>

  2573. <span class="n">context</span> <span class="o">=</span> <span class="n">ssl</span><span class="o">.</span><span class="n">create_default_context</span><span class="p">(</span><span class="n">cafile</span><span class="o">=</span><span class="s2">&quot;/path/to/file.crt&quot;</span><span class="p">)</span>

  2574. 

  2575. <span class="n">urllib2</span><span class="o">.</span><span class="n">urlopen</span><span class="p">(</span><span class="s2">&quot;https://invalid-cert&quot;</span><span class="p">,</span> <span class="n">context</span><span class="o">=</span><span class="n">context</span><span class="p">)</span>

  2576. </pre></div>

  2577. </div>

  2578. </section>

  2579. <section id="pep-493-https-verification-migration-tools-for-python-2-7">

  2580. <h3>PEP 493: HTTPS verification migration tools for Python 2.7<a class="headerlink" href="#pep-493-https-verification-migration-tools-for-python-2-7" title="Link to this heading">¶</a></h3>

  2581. <p><span class="target" id="index-23"></span><a class="pep reference external" href="https://peps.python.org/pep-0493/"><strong>PEP 493</strong></a> provides additional migration tools to support a more incremental

  2582. infrastructure upgrade process for environments containing applications and

  2583. services relying on the historically permissive processing of server

  2584. certificates when establishing client HTTPS connections.  These additions were

  2585. made in the Python 2.7.12 release.</p>

  2586. <p>These tools are intended for use in cases where affected applications and

  2587. services can’t be modified to explicitly pass a more permissive SSL context

  2588. when establishing the connection.</p>

  2589. <p>For applications and services which can’t be modified at all, the new

  2590. <code class="docutils literal notranslate"><span class="pre">PYTHONHTTPSVERIFY</span></code> environment variable may be set to <code class="docutils literal notranslate"><span class="pre">0</span></code> to revert an

  2591. entire Python process back to the default permissive behaviour of Python 2.7.8

  2592. and earlier.</p>

  2593. <p>For cases where the connection establishment code can’t be modified, but the

  2594. overall application can be, the new <code class="xref py py-func docutils literal notranslate"><span class="pre">ssl._https_verify_certificates()</span></code>

  2595. function can be used to adjust the default behaviour at runtime.</p>

  2596. </section>

  2597. <section id="new-make-regen-all-build-target">

  2598. <h3>New <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">regen-all</span></code> build target<a class="headerlink" href="#new-make-regen-all-build-target" title="Link to this heading">¶</a></h3>

  2599. <p>To simplify cross-compilation, and to ensure that CPython can reliably be

  2600. compiled without requiring an existing version of Python to already be

  2601. available, the autotools-based build system no longer attempts to implicitly

  2602. recompile generated files based on file modification times.</p>

  2603. <p>Instead, a new <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">regen-all</span></code> command has been added to force regeneration

  2604. of these files when desired (e.g. after an initial version of Python has

  2605. already been built based on the pregenerated versions).</p>

  2606. <p>More selective regeneration targets are also defined - see

  2607. <a class="reference external" href="https://github.com/python/cpython/tree/3.12/Makefile.pre.in">Makefile.pre.in</a> for details.</p>

  2608. <p>(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=23404">bpo-23404</a>.)</p>

  2609. <div class="versionadded">

  2610. <p><span class="versionmodified added">New in version 2.7.14.</span></p>

  2611. </div>

  2612. </section>

  2613. <section id="removal-of-make-touch-build-target">

  2614. <h3>Removal of <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">touch</span></code> build target<a class="headerlink" href="#removal-of-make-touch-build-target" title="Link to this heading">¶</a></h3>

  2615. <p>The <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">touch</span></code> build target previously used to request implicit regeneration

  2616. of generated files by updating their modification times has been removed.</p>

  2617. <p>It has been replaced by the new <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">regen-all</span></code> target.</p>

  2618. <p>(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=23404">bpo-23404</a>.)</p>

  2619. <div class="versionchanged">

  2620. <p><span class="versionmodified changed">Changed in version 2.7.14.</span></p>

  2621. </div>

  2622. </section>

  2623. </section>

  2624. <section id="acknowledgements">

  2625. <span id="acks27"></span><h2>Acknowledgements<a class="headerlink" href="#acknowledgements" title="Link to this heading">¶</a></h2>

  2626. <p>The author would like to thank the following people for offering

  2627. suggestions, corrections and assistance with various drafts of this

  2628. article: Nick Coghlan, Philip Jenvey, Ryan Lovett, R. David Murray,

  2629. Hugh Secker-Walker.</p>

  2630. </section>

  2631. </section>

  2632. 

  2633. 

  2634.             <div class="clearer"></div>

  2635.           </div>

  2636.         </div>

  2637.       </div>

  2638.       <div class="sphinxsidebar" role="navigation" aria-label="main navigation">

  2639.         <div class="sphinxsidebarwrapper">

  2640.   <div>

  2641.     <h3><a href="../contents.html">Table of Contents</a></h3>

  2642.     <ul>

  2643. <li><a class="reference internal" href="#">What’s New in Python 2.7</a><ul>

  2644. <li><a class="reference internal" href="#the-future-for-python-2-x">The Future for Python 2.x</a></li>

  2645. <li><a class="reference internal" href="#changes-to-the-handling-of-deprecation-warnings">Changes to the Handling of Deprecation Warnings</a></li>

  2646. <li><a class="reference internal" href="#python-3-1-features">Python 3.1 Features</a></li>

  2647. <li><a class="reference internal" href="#pep-372-adding-an-ordered-dictionary-to-collections">PEP 372: Adding an Ordered Dictionary to collections</a></li>

  2648. <li><a class="reference internal" href="#pep-378-format-specifier-for-thousands-separator">PEP 378: Format Specifier for Thousands Separator</a></li>

  2649. <li><a class="reference internal" href="#pep-389-the-argparse-module-for-parsing-command-lines">PEP 389: The argparse Module for Parsing Command Lines</a></li>

  2650. <li><a class="reference internal" href="#pep-391-dictionary-based-configuration-for-logging">PEP 391: Dictionary-Based Configuration For Logging</a></li>

  2651. <li><a class="reference internal" href="#pep-3106-dictionary-views">PEP 3106: Dictionary Views</a></li>

  2652. <li><a class="reference internal" href="#pep-3137-the-memoryview-object">PEP 3137: The memoryview Object</a></li>

  2653. <li><a class="reference internal" href="#other-language-changes">Other Language Changes</a><ul>

  2654. <li><a class="reference internal" href="#interpreter-changes">Interpreter Changes</a></li>

  2655. <li><a class="reference internal" href="#optimizations">Optimizations</a></li>

  2656. </ul>

  2657. </li>

  2658. <li><a class="reference internal" href="#new-and-improved-modules">New and Improved Modules</a><ul>

  2659. <li><a class="reference internal" href="#new-module-importlib">New module: importlib</a></li>

  2660. <li><a class="reference internal" href="#new-module-sysconfig">New module: sysconfig</a></li>

  2661. <li><a class="reference internal" href="#ttk-themed-widgets-for-tk">ttk: Themed Widgets for Tk</a></li>

  2662. <li><a class="reference internal" href="#updated-module-unittest">Updated module: unittest</a></li>

  2663. <li><a class="reference internal" href="#updated-module-elementtree-1-3">Updated module: ElementTree 1.3</a></li>

  2664. </ul>

  2665. </li>

  2666. <li><a class="reference internal" href="#build-and-c-api-changes">Build and C API Changes</a><ul>

  2667. <li><a class="reference internal" href="#capsules">Capsules</a></li>

  2668. <li><a class="reference internal" href="#port-specific-changes-windows">Port-Specific Changes: Windows</a></li>

  2669. <li><a class="reference internal" href="#port-specific-changes-mac-os-x">Port-Specific Changes: Mac OS X</a></li>

  2670. <li><a class="reference internal" href="#port-specific-changes-freebsd">Port-Specific Changes: FreeBSD</a></li>

  2671. </ul>

  2672. </li>

  2673. <li><a class="reference internal" href="#other-changes-and-fixes">Other Changes and Fixes</a></li>

  2674. <li><a class="reference internal" href="#porting-to-python-2-7">Porting to Python 2.7</a></li>

  2675. <li><a class="reference internal" href="#new-features-added-to-python-2-7-maintenance-releases">New Features Added to Python 2.7 Maintenance Releases</a><ul>

  2676. <li><a class="reference internal" href="#two-new-environment-variables-for-debug-mode">Two new environment variables for debug mode</a></li>

  2677. <li><a class="reference internal" href="#pep-434-idle-enhancement-exception-for-all-branches">PEP 434: IDLE Enhancement Exception for All Branches</a></li>

  2678. <li><a class="reference internal" href="#pep-466-network-security-enhancements-for-python-2-7">PEP 466: Network Security Enhancements for Python 2.7</a></li>

  2679. <li><a class="reference internal" href="#pep-477-backport-ensurepip-pep-453-to-python-2-7">PEP 477: Backport ensurepip (PEP 453) to Python 2.7</a><ul>

  2680. <li><a class="reference internal" href="#bootstrapping-pip-by-default">Bootstrapping pip By Default</a></li>

  2681. <li><a class="reference internal" href="#documentation-changes">Documentation Changes</a></li>

  2682. </ul>

  2683. </li>

  2684. <li><a class="reference internal" href="#pep-476-enabling-certificate-verification-by-default-for-stdlib-http-clients">PEP 476: Enabling certificate verification by default for stdlib http clients</a></li>

  2685. <li><a class="reference internal" href="#pep-493-https-verification-migration-tools-for-python-2-7">PEP 493: HTTPS verification migration tools for Python 2.7</a></li>

  2686. <li><a class="reference internal" href="#new-make-regen-all-build-target">New <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">regen-all</span></code> build target</a></li>

  2687. <li><a class="reference internal" href="#removal-of-make-touch-build-target">Removal of <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">touch</span></code> build target</a></li>

  2688. </ul>

  2689. </li>

  2690. <li><a class="reference internal" href="#acknowledgements">Acknowledgements</a></li>

  2691. </ul>

  2692. </li>

  2693. </ul>

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