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  96.     <h3><a href="../contents.html">Table of Contents</a></h3>

  97.     <ul>

  98. <li><a class="reference internal" href="#">What’s New In Python 3.3</a><ul>

  99. <li><a class="reference internal" href="#summary-release-highlights">Summary – Release highlights</a></li>

  100. <li><a class="reference internal" href="#pep-405-virtual-environments">PEP 405: Virtual Environments</a></li>

  101. <li><a class="reference internal" href="#pep-420-implicit-namespace-packages">PEP 420: Implicit Namespace Packages</a></li>

  102. <li><a class="reference internal" href="#pep-3118-new-memoryview-implementation-and-buffer-protocol-documentation">PEP 3118: New memoryview implementation and buffer protocol documentation</a><ul>

  103. <li><a class="reference internal" href="#features">Features</a></li>

  104. <li><a class="reference internal" href="#api-changes">API changes</a></li>

  105. </ul>

  106. </li>

  107. <li><a class="reference internal" href="#pep-393-flexible-string-representation">PEP 393: Flexible String Representation</a><ul>

  108. <li><a class="reference internal" href="#functionality">Functionality</a></li>

  109. <li><a class="reference internal" href="#performance-and-resource-usage">Performance and resource usage</a></li>

  110. </ul>

  111. </li>

  112. <li><a class="reference internal" href="#pep-397-python-launcher-for-windows">PEP 397: Python Launcher for Windows</a></li>

  113. <li><a class="reference internal" href="#pep-3151-reworking-the-os-and-io-exception-hierarchy">PEP 3151: Reworking the OS and IO exception hierarchy</a></li>

  114. <li><a class="reference internal" href="#pep-380-syntax-for-delegating-to-a-subgenerator">PEP 380: Syntax for Delegating to a Subgenerator</a></li>

  115. <li><a class="reference internal" href="#pep-409-suppressing-exception-context">PEP 409: Suppressing exception context</a></li>

  116. <li><a class="reference internal" href="#pep-414-explicit-unicode-literals">PEP 414: Explicit Unicode literals</a></li>

  117. <li><a class="reference internal" href="#pep-3155-qualified-name-for-classes-and-functions">PEP 3155: Qualified name for classes and functions</a></li>

  118. <li><a class="reference internal" href="#pep-412-key-sharing-dictionary">PEP 412: Key-Sharing Dictionary</a></li>

  119. <li><a class="reference internal" href="#pep-362-function-signature-object">PEP 362: Function Signature Object</a></li>

  120. <li><a class="reference internal" href="#pep-421-adding-sys-implementation">PEP 421: Adding sys.implementation</a><ul>

  121. <li><a class="reference internal" href="#simplenamespace">SimpleNamespace</a></li>

  122. </ul>

  123. </li>

  124. <li><a class="reference internal" href="#using-importlib-as-the-implementation-of-import">Using importlib as the Implementation of Import</a><ul>

  125. <li><a class="reference internal" href="#new-apis">New APIs</a></li>

  126. <li><a class="reference internal" href="#visible-changes">Visible Changes</a></li>

  127. </ul>

  128. </li>

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

  130. <li><a class="reference internal" href="#a-finer-grained-import-lock">A Finer-Grained Import Lock</a></li>

  131. <li><a class="reference internal" href="#builtin-functions-and-types">Builtin functions and types</a></li>

  132. <li><a class="reference internal" href="#new-modules">New Modules</a><ul>

  133. <li><a class="reference internal" href="#faulthandler">faulthandler</a></li>

  134. <li><a class="reference internal" href="#ipaddress">ipaddress</a></li>

  135. <li><a class="reference internal" href="#lzma">lzma</a></li>

  136. </ul>

  137. </li>

  138. <li><a class="reference internal" href="#improved-modules">Improved Modules</a><ul>

  139. <li><a class="reference internal" href="#abc">abc</a></li>

  140. <li><a class="reference internal" href="#array">array</a></li>

  141. <li><a class="reference internal" href="#base64">base64</a></li>

  142. <li><a class="reference internal" href="#binascii">binascii</a></li>

  143. <li><a class="reference internal" href="#bz2">bz2</a></li>

  144. <li><a class="reference internal" href="#codecs">codecs</a></li>

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

  146. <li><a class="reference internal" href="#contextlib">contextlib</a></li>

  147. <li><a class="reference internal" href="#crypt">crypt</a></li>

  148. <li><a class="reference internal" href="#curses">curses</a></li>

  149. <li><a class="reference internal" href="#datetime">datetime</a></li>

  150. <li><a class="reference internal" href="#decimal">decimal</a><ul>

  151. <li><a class="reference internal" href="#id1">Features</a></li>

  152. <li><a class="reference internal" href="#id2">API changes</a></li>

  153. </ul>

  154. </li>

  155. <li><a class="reference internal" href="#email">email</a><ul>

  156. <li><a class="reference internal" href="#policy-framework">Policy Framework</a></li>

  157. <li><a class="reference internal" href="#provisional-policy-with-new-header-api">Provisional Policy with New Header API</a></li>

  158. <li><a class="reference internal" href="#other-api-changes">Other API Changes</a></li>

  159. </ul>

  160. </li>

  161. <li><a class="reference internal" href="#ftplib">ftplib</a></li>

  162. <li><a class="reference internal" href="#functools">functools</a></li>

  163. <li><a class="reference internal" href="#gc">gc</a></li>

  164. <li><a class="reference internal" href="#hmac">hmac</a></li>

  165. <li><a class="reference internal" href="#http">http</a></li>

  166. <li><a class="reference internal" href="#html">html</a></li>

  167. <li><a class="reference internal" href="#imaplib">imaplib</a></li>

  168. <li><a class="reference internal" href="#inspect">inspect</a></li>

  169. <li><a class="reference internal" href="#io">io</a></li>

  170. <li><a class="reference internal" href="#itertools">itertools</a></li>

  171. <li><a class="reference internal" href="#logging">logging</a></li>

  172. <li><a class="reference internal" href="#math">math</a></li>

  173. <li><a class="reference internal" href="#mmap">mmap</a></li>

  174. <li><a class="reference internal" href="#multiprocessing">multiprocessing</a></li>

  175. <li><a class="reference internal" href="#nntplib">nntplib</a></li>

  176. <li><a class="reference internal" href="#os">os</a></li>

  177. <li><a class="reference internal" href="#pdb">pdb</a></li>

  178. <li><a class="reference internal" href="#pickle">pickle</a></li>

  179. <li><a class="reference internal" href="#pydoc">pydoc</a></li>

  180. <li><a class="reference internal" href="#re">re</a></li>

  181. <li><a class="reference internal" href="#sched">sched</a></li>

  182. <li><a class="reference internal" href="#select">select</a></li>

  183. <li><a class="reference internal" href="#shlex">shlex</a></li>

  184. <li><a class="reference internal" href="#shutil">shutil</a></li>

  185. <li><a class="reference internal" href="#signal">signal</a></li>

  186. <li><a class="reference internal" href="#smtpd">smtpd</a></li>

  187. <li><a class="reference internal" href="#smtplib">smtplib</a></li>

  188. <li><a class="reference internal" href="#socket">socket</a></li>

  189. <li><a class="reference internal" href="#socketserver">socketserver</a></li>

  190. <li><a class="reference internal" href="#sqlite3">sqlite3</a></li>

  191. <li><a class="reference internal" href="#ssl">ssl</a></li>

  192. <li><a class="reference internal" href="#stat">stat</a></li>

  193. <li><a class="reference internal" href="#struct">struct</a></li>

  194. <li><a class="reference internal" href="#subprocess">subprocess</a></li>

  195. <li><a class="reference internal" href="#sys">sys</a></li>

  196. <li><a class="reference internal" href="#tarfile">tarfile</a></li>

  197. <li><a class="reference internal" href="#tempfile">tempfile</a></li>

  198. <li><a class="reference internal" href="#textwrap">textwrap</a></li>

  199. <li><a class="reference internal" href="#threading">threading</a></li>

  200. <li><a class="reference internal" href="#time">time</a></li>

  201. <li><a class="reference internal" href="#types">types</a></li>

  202. <li><a class="reference internal" href="#unittest">unittest</a></li>

  203. <li><a class="reference internal" href="#urllib">urllib</a></li>

  204. <li><a class="reference internal" href="#webbrowser">webbrowser</a></li>

  205. <li><a class="reference internal" href="#xml-etree-elementtree">xml.etree.ElementTree</a></li>

  206. <li><a class="reference internal" href="#zlib">zlib</a></li>

  207. </ul>

  208. </li>

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

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

  211. <li><a class="reference internal" href="#deprecated">Deprecated</a><ul>

  212. <li><a class="reference internal" href="#unsupported-operating-systems">Unsupported Operating Systems</a></li>

  213. <li><a class="reference internal" href="#deprecated-python-modules-functions-and-methods">Deprecated Python modules, functions and methods</a></li>

  214. <li><a class="reference internal" href="#deprecated-functions-and-types-of-the-c-api">Deprecated functions and types of the C API</a></li>

  215. <li><a class="reference internal" href="#deprecated-features">Deprecated features</a></li>

  216. </ul>

  217. </li>

  218. <li><a class="reference internal" href="#porting-to-python-3-3">Porting to Python 3.3</a><ul>

  219. <li><a class="reference internal" href="#porting-python-code">Porting Python code</a></li>

  220. <li><a class="reference internal" href="#porting-c-code">Porting C code</a></li>

  221. <li><a class="reference internal" href="#building-c-extensions">Building C extensions</a></li>

  222. <li><a class="reference internal" href="#command-line-switch-changes">Command Line Switch Changes</a></li>

  223. </ul>

  224. </li>

  225. </ul>

  226. </li>

  227. </ul>

  228. 

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  230.   <div>

  231.     <h4>Previous topic</h4>

  232.     <p class="topless"><a href="3.4.html"

  233.                           title="previous chapter">What’s New In Python 3.4</a></p>

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  237.     <p class="topless"><a href="3.2.html"

  238.                           title="next chapter">What’s New In Python 3.2</a></p>

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  316.   <section id="what-s-new-in-python-3-3">

  317. <h1>What’s New In Python 3.3<a class="headerlink" href="#what-s-new-in-python-3-3" title="Link to this heading">¶</a></h1>

  318. <p>This article explains the new features in Python 3.3, compared to 3.2.

  319. Python 3.3 was released on September 29, 2012.  For full details,

  320. see the <a class="reference external" href="https://docs.python.org/3.3/whatsnew/changelog.html">changelog</a>.</p>

  321. <div class="admonition seealso">

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

  323. <p><span class="target" id="index-0"></span><a class="pep reference external" href="https://peps.python.org/pep-0398/"><strong>PEP 398</strong></a> - Python 3.3 Release Schedule</p>

  324. </div>

  325. <section id="summary-release-highlights">

  326. <h2>Summary – Release highlights<a class="headerlink" href="#summary-release-highlights" title="Link to this heading">¶</a></h2>

  327. <p>New syntax features:</p>

  328. <ul class="simple">

  329. <li><p>New <code class="docutils literal notranslate"><span class="pre">yield</span> <span class="pre">from</span></code> expression for <a class="reference internal" href="#pep-380"><span class="std std-ref">generator delegation</span></a>.</p></li>

  330. <li><p>The <code class="docutils literal notranslate"><span class="pre">u'unicode'</span></code> syntax is accepted again for <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> objects.</p></li>

  331. </ul>

  332. <p>New library modules:</p>

  333. <ul class="simple">

  334. <li><p><a class="reference internal" href="../library/faulthandler.html#module-faulthandler" title="faulthandler: Dump the Python traceback."><code class="xref py py-mod docutils literal notranslate"><span class="pre">faulthandler</span></code></a> (helps debugging low-level crashes)</p></li>

  335. <li><p><a class="reference internal" href="../library/ipaddress.html#module-ipaddress" title="ipaddress: IPv4/IPv6 manipulation library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ipaddress</span></code></a> (high-level objects representing IP addresses and masks)</p></li>

  336. <li><p><a class="reference internal" href="../library/lzma.html#module-lzma" title="lzma: A Python wrapper for the liblzma compression library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">lzma</span></code></a> (compress data using the XZ / LZMA algorithm)</p></li>

  337. <li><p><a class="reference internal" href="../library/unittest.mock.html#module-unittest.mock" title="unittest.mock: Mock object library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">unittest.mock</span></code></a> (replace parts of your system under test with mock objects)</p></li>

  338. <li><p><a class="reference internal" href="../library/venv.html#module-venv" title="venv: Creation of virtual environments."><code class="xref py py-mod docutils literal notranslate"><span class="pre">venv</span></code></a> (Python <a class="reference internal" href="#pep-405"><span class="std std-ref">virtual environments</span></a>, as in the

  339. popular <code class="docutils literal notranslate"><span class="pre">virtualenv</span></code> package)</p></li>

  340. </ul>

  341. <p>New built-in features:</p>

  342. <ul class="simple">

  343. <li><p>Reworked <a class="reference internal" href="#pep-3151"><span class="std std-ref">I/O exception hierarchy</span></a>.</p></li>

  344. </ul>

  345. <p>Implementation improvements:</p>

  346. <ul class="simple">

  347. <li><p>Rewritten <a class="reference internal" href="#importlib"><span class="std std-ref">import machinery</span></a> based on <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>.</p></li>

  348. <li><p>More compact <a class="reference internal" href="#pep-393"><span class="std std-ref">unicode strings</span></a>.</p></li>

  349. <li><p>More compact <a class="reference internal" href="#pep-412"><span class="std std-ref">attribute dictionaries</span></a>.</p></li>

  350. </ul>

  351. <p>Significantly Improved Library Modules:</p>

  352. <ul class="simple">

  353. <li><p>C Accelerator for the <a class="reference internal" href="#new-decimal"><span class="std std-ref">decimal</span></a> module.</p></li>

  354. <li><p>Better unicode handling in the <a class="reference internal" href="#new-email"><span class="std std-ref">email</span></a> module

  355. (<a class="reference internal" href="../glossary.html#term-provisional-package"><span class="xref std std-term">provisional</span></a>).</p></li>

  356. </ul>

  357. <p>Security improvements:</p>

  358. <ul class="simple">

  359. <li><p>Hash randomization is switched on by default.</p></li>

  360. </ul>

  361. <p>Please read on for a comprehensive list of user-facing changes.</p>

  362. </section>

  363. <section id="pep-405-virtual-environments">

  364. <span id="pep-405"></span><h2>PEP 405: Virtual Environments<a class="headerlink" href="#pep-405-virtual-environments" title="Link to this heading">¶</a></h2>

  365. <p>Virtual environments help create separate Python setups while sharing a

  366. system-wide base install, for ease of maintenance.  Virtual environments

  367. have their own set of private site packages (i.e. locally installed

  368. libraries), and are optionally segregated from the system-wide site

  369. packages.  Their concept and implementation are inspired by the popular

  370. <code class="docutils literal notranslate"><span class="pre">virtualenv</span></code> third-party package, but benefit from tighter integration

  371. with the interpreter core.</p>

  372. <p>This PEP adds the <a class="reference internal" href="../library/venv.html#module-venv" title="venv: Creation of virtual environments."><code class="xref py py-mod docutils literal notranslate"><span class="pre">venv</span></code></a> module for programmatic access, and the

  373. <code class="docutils literal notranslate"><span class="pre">pyvenv</span></code> script for command-line access and

  374. administration.  The Python interpreter checks for a <code class="docutils literal notranslate"><span class="pre">pyvenv.cfg</span></code>,

  375. file whose existence signals the base of a virtual environment’s directory

  376. tree.</p>

  377. <div class="admonition seealso">

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

  379. <dl class="simple">

  380. <dt><span class="target" id="index-1"></span><a class="pep reference external" href="https://peps.python.org/pep-0405/"><strong>PEP 405</strong></a> - Python Virtual Environments</dt><dd><p>PEP written by Carl Meyer; implementation by Carl Meyer and Vinay Sajip</p>

  381. </dd>

  382. </dl>

  383. </div>

  384. </section>

  385. <section id="pep-420-implicit-namespace-packages">

  386. <h2>PEP 420: Implicit Namespace Packages<a class="headerlink" href="#pep-420-implicit-namespace-packages" title="Link to this heading">¶</a></h2>

  387. <p>Native support for package directories that don’t require <code class="docutils literal notranslate"><span class="pre">__init__.py</span></code>

  388. marker files and can automatically span multiple path segments (inspired by

  389. various third party approaches to namespace packages, as described in

  390. <span class="target" id="index-2"></span><a class="pep reference external" href="https://peps.python.org/pep-0420/"><strong>PEP 420</strong></a>)</p>

  391. <div class="admonition seealso">

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

  393. <dl class="simple">

  394. <dt><span class="target" id="index-3"></span><a class="pep reference external" href="https://peps.python.org/pep-0420/"><strong>PEP 420</strong></a> - Implicit Namespace Packages</dt><dd><p>PEP written by Eric V. Smith; implementation by Eric V. Smith

  395. and Barry Warsaw</p>

  396. </dd>

  397. </dl>

  398. </div>

  399. </section>

  400. <section id="pep-3118-new-memoryview-implementation-and-buffer-protocol-documentation">

  401. <span id="pep-3118-update"></span><h2>PEP 3118: New memoryview implementation and buffer protocol documentation<a class="headerlink" href="#pep-3118-new-memoryview-implementation-and-buffer-protocol-documentation" title="Link to this heading">¶</a></h2>

  402. <p>The implementation of <span class="target" id="index-4"></span><a class="pep reference external" href="https://peps.python.org/pep-3118/"><strong>PEP 3118</strong></a> has been significantly improved.</p>

  403. <p>The new memoryview implementation comprehensively fixes all ownership and

  404. lifetime issues of dynamically allocated fields in the Py_buffer struct

  405. that led to multiple crash reports. Additionally, several functions that

  406. crashed or returned incorrect results for non-contiguous or multi-dimensional

  407. input have been fixed.</p>

  408. <p>The memoryview object now has a PEP-3118 compliant getbufferproc()

  409. that checks the consumer’s request type. Many new features have been

  410. added, most of them work in full generality for non-contiguous arrays

  411. and arrays with suboffsets.</p>

  412. <p>The documentation has been updated, clearly spelling out responsibilities

  413. for both exporters and consumers. Buffer request flags are grouped into

  414. basic and compound flags. The memory layout of non-contiguous and

  415. multi-dimensional NumPy-style arrays is explained.</p>

  416. <section id="features">

  417. <h3>Features<a class="headerlink" href="#features" title="Link to this heading">¶</a></h3>

  418. <ul class="simple">

  419. <li><p>All native single character format specifiers in struct module syntax

  420. (optionally prefixed with ‘&#64;’) are now supported.</p></li>

  421. <li><p>With some restrictions, the cast() method allows changing of format and

  422. shape of C-contiguous arrays.</p></li>

  423. <li><p>Multi-dimensional list representations are supported for any array type.</p></li>

  424. <li><p>Multi-dimensional comparisons are supported for any array type.</p></li>

  425. <li><p>One-dimensional memoryviews of hashable (read-only) types with formats B,

  426. b or c are now hashable.  (Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13411">bpo-13411</a>.)</p></li>

  427. <li><p>Arbitrary slicing of any 1-D arrays type is supported. For example, it

  428. is now possible to reverse a memoryview in <em>O</em>(1) by using a negative step.</p></li>

  429. </ul>

  430. </section>

  431. <section id="api-changes">

  432. <h3>API changes<a class="headerlink" href="#api-changes" title="Link to this heading">¶</a></h3>

  433. <ul class="simple">

  434. <li><p>The maximum number of dimensions is officially limited to 64.</p></li>

  435. <li><p>The representation of empty shape, strides and suboffsets is now

  436. an empty tuple instead of <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p></li>

  437. <li><p>Accessing a memoryview element with format ‘B’ (unsigned bytes)

  438. now returns an integer (in accordance with the struct module syntax).

  439. For returning a bytes object the view must be cast to ‘c’ first.</p></li>

  440. <li><p>memoryview comparisons now use the logical structure of the operands

  441. and compare all array elements by value. All format strings in struct

  442. module syntax are supported. Views with unrecognised format strings

  443. are still permitted, but will always compare as unequal, regardless

  444. of view contents.</p></li>

  445. <li><p>For further changes see <a class="reference internal" href="#build-and-c-api-changes">Build and C API Changes</a> and <a class="reference internal" href="#porting-c-code">Porting C code</a>.</p></li>

  446. </ul>

  447. <p>(Contributed by Stefan Krah in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10181">bpo-10181</a>.)</p>

  448. <div class="admonition seealso">

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

  450. <p><span class="target" id="index-5"></span><a class="pep reference external" href="https://peps.python.org/pep-3118/"><strong>PEP 3118</strong></a> - Revising the Buffer Protocol</p>

  451. </div>

  452. </section>

  453. </section>

  454. <section id="pep-393-flexible-string-representation">

  455. <span id="pep-393"></span><h2>PEP 393: Flexible String Representation<a class="headerlink" href="#pep-393-flexible-string-representation" title="Link to this heading">¶</a></h2>

  456. <p>The Unicode string type is changed to support multiple internal

  457. representations, depending on the character with the largest Unicode ordinal

  458. (1, 2, or 4 bytes) in the represented string.  This allows a space-efficient

  459. representation in common cases, but gives access to full UCS-4 on all

  460. systems.  For compatibility with existing APIs, several representations may

  461. exist in parallel; over time, this compatibility should be phased out.</p>

  462. <p>On the Python side, there should be no downside to this change.</p>

  463. <p>On the C API side, <span class="target" id="index-6"></span><a class="pep reference external" href="https://peps.python.org/pep-0393/"><strong>PEP 393</strong></a> is fully backward compatible.  The legacy API

  464. should remain available at least five years.  Applications using the legacy

  465. API will not fully benefit of the memory reduction, or - worse - may use

  466. a bit more memory, because Python may have to maintain two versions of each

  467. string (in the legacy format and in the new efficient storage).</p>

  468. <section id="functionality">

  469. <h3>Functionality<a class="headerlink" href="#functionality" title="Link to this heading">¶</a></h3>

  470. <p>Changes introduced by <span class="target" id="index-7"></span><a class="pep reference external" href="https://peps.python.org/pep-0393/"><strong>PEP 393</strong></a> are the following:</p>

  471. <ul class="simple">

  472. <li><p>Python now always supports the full range of Unicode code points, including

  473. non-BMP ones (i.e. from <code class="docutils literal notranslate"><span class="pre">U+0000</span></code> to <code class="docutils literal notranslate"><span class="pre">U+10FFFF</span></code>).  The distinction between

  474. narrow and wide builds no longer exists and Python now behaves like a wide

  475. build, even under Windows.</p></li>

  476. <li><p>With the death of narrow builds, the problems specific to narrow builds have

  477. also been fixed, for example:</p>

  478. <ul>

  479. <li><p><a class="reference internal" href="../library/functions.html#len" title="len"><code class="xref py py-func docutils literal notranslate"><span class="pre">len()</span></code></a> now always returns 1 for non-BMP characters,

  480. so <code class="docutils literal notranslate"><span class="pre">len('\U0010FFFF')</span> <span class="pre">==</span> <span class="pre">1</span></code>;</p></li>

  481. <li><p>surrogate pairs are not recombined in string literals,

  482. so <code class="docutils literal notranslate"><span class="pre">'\uDBFF\uDFFF'</span> <span class="pre">!=</span> <span class="pre">'\U0010FFFF'</span></code>;</p></li>

  483. <li><p>indexing or slicing non-BMP characters returns the expected value,

  484. so <code class="docutils literal notranslate"><span class="pre">'\U0010FFFF'[0]</span></code> now returns <code class="docutils literal notranslate"><span class="pre">'\U0010FFFF'</span></code> and not <code class="docutils literal notranslate"><span class="pre">'\uDBFF'</span></code>;</p></li>

  485. <li><p>all other functions in the standard library now correctly handle

  486. non-BMP code points.</p></li>

  487. </ul>

  488. </li>

  489. <li><p>The value of <a class="reference internal" href="../library/sys.html#sys.maxunicode" title="sys.maxunicode"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.maxunicode</span></code></a> is now always <code class="docutils literal notranslate"><span class="pre">1114111</span></code> (<code class="docutils literal notranslate"><span class="pre">0x10FFFF</span></code>

  490. in hexadecimal).  The <code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_GetMax()</span></code> function still returns

  491. either <code class="docutils literal notranslate"><span class="pre">0xFFFF</span></code> or <code class="docutils literal notranslate"><span class="pre">0x10FFFF</span></code> for backward compatibility, and it should

  492. not be used with the new Unicode API (see <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13054">bpo-13054</a>).</p></li>

  493. <li><p>The <code class="file docutils literal notranslate"><span class="pre">./configure</span></code> flag <code class="docutils literal notranslate"><span class="pre">--with-wide-unicode</span></code> has been removed.</p></li>

  494. </ul>

  495. </section>

  496. <section id="performance-and-resource-usage">

  497. <h3>Performance and resource usage<a class="headerlink" href="#performance-and-resource-usage" title="Link to this heading">¶</a></h3>

  498. <p>The storage of Unicode strings now depends on the highest code point in the string:</p>

  499. <ul class="simple">

  500. <li><p>pure ASCII and Latin1 strings (<code class="docutils literal notranslate"><span class="pre">U+0000-U+00FF</span></code>) use 1 byte per code point;</p></li>

  501. <li><p>BMP strings (<code class="docutils literal notranslate"><span class="pre">U+0000-U+FFFF</span></code>) use 2 bytes per code point;</p></li>

  502. <li><p>non-BMP strings (<code class="docutils literal notranslate"><span class="pre">U+10000-U+10FFFF</span></code>) use 4 bytes per code point.</p></li>

  503. </ul>

  504. <p>The net effect is that for most applications, memory usage of string

  505. storage should decrease significantly - especially compared to former

  506. wide unicode builds - as, in many cases, strings will be pure ASCII

  507. even in international contexts (because many strings store non-human

  508. language data, such as XML fragments, HTTP headers, JSON-encoded data,

  509. etc.).  We also hope that it will, for the same reasons, increase CPU

  510. cache efficiency on non-trivial applications. The memory usage of

  511. Python 3.3 is two to three times smaller than Python 3.2, and a little

  512. bit better than Python 2.7, on a Django benchmark (see the PEP for

  513. details).</p>

  514. <div class="admonition seealso">

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

  516. <dl class="simple">

  517. <dt><span class="target" id="index-8"></span><a class="pep reference external" href="https://peps.python.org/pep-0393/"><strong>PEP 393</strong></a> - Flexible String Representation</dt><dd><p>PEP written by Martin von Löwis; implementation by Torsten Becker

  518. and Martin von Löwis.</p>

  519. </dd>

  520. </dl>

  521. </div>

  522. </section>

  523. </section>

  524. <section id="pep-397-python-launcher-for-windows">

  525. <span id="pep-397"></span><h2>PEP 397: Python Launcher for Windows<a class="headerlink" href="#pep-397-python-launcher-for-windows" title="Link to this heading">¶</a></h2>

  526. <p>The Python 3.3 Windows installer now includes a <code class="docutils literal notranslate"><span class="pre">py</span></code> launcher application

  527. that can be used to launch Python applications in a version independent

  528. fashion.</p>

  529. <p>This launcher is invoked implicitly when double-clicking <code class="docutils literal notranslate"><span class="pre">*.py</span></code> files.

  530. If only a single Python version is installed on the system, that version

  531. will be used to run the file. If multiple versions are installed, the most

  532. recent version is used by default, but this can be overridden by including

  533. a Unix-style “shebang line” in the Python script.</p>

  534. <p>The launcher can also be used explicitly from the command line as the <code class="docutils literal notranslate"><span class="pre">py</span></code>

  535. application. Running <code class="docutils literal notranslate"><span class="pre">py</span></code> follows the same version selection rules as

  536. implicitly launching scripts, but a more specific version can be selected

  537. by passing appropriate arguments (such as <code class="docutils literal notranslate"><span class="pre">-3</span></code> to request Python 3 when

  538. Python 2 is also installed, or <code class="docutils literal notranslate"><span class="pre">-2.6</span></code> to specifically request an earlier

  539. Python version when a more recent version is installed).</p>

  540. <p>In addition to the launcher, the Windows installer now includes an

  541. option to add the newly installed Python to the system PATH.  (Contributed

  542. by Brian Curtin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3561">bpo-3561</a>.)</p>

  543. <div class="admonition seealso">

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

  545. <dl class="simple">

  546. <dt><span class="target" id="index-9"></span><a class="pep reference external" href="https://peps.python.org/pep-0397/"><strong>PEP 397</strong></a> - Python Launcher for Windows</dt><dd><p>PEP written by Mark Hammond and Martin v. Löwis; implementation by

  547. Vinay Sajip.</p>

  548. </dd>

  549. </dl>

  550. <p>Launcher documentation: <a class="reference internal" href="../using/windows.html#launcher"><span class="std std-ref">Python Launcher for Windows</span></a></p>

  551. <p>Installer PATH modification: <a class="reference internal" href="../using/windows.html#windows-path-mod"><span class="std std-ref">Finding the Python executable</span></a></p>

  552. </div>

  553. </section>

  554. <section id="pep-3151-reworking-the-os-and-io-exception-hierarchy">

  555. <span id="pep-3151"></span><h2>PEP 3151: Reworking the OS and IO exception hierarchy<a class="headerlink" href="#pep-3151-reworking-the-os-and-io-exception-hierarchy" title="Link to this heading">¶</a></h2>

  556. <p>The hierarchy of exceptions raised by operating system errors is now both

  557. simplified and finer-grained.</p>

  558. <p>You don’t have to worry anymore about choosing the appropriate exception

  559. type between <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>, <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>, <a class="reference internal" href="../library/exceptions.html#EnvironmentError" title="EnvironmentError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">EnvironmentError</span></code></a>,

  560. <a class="reference internal" href="../library/exceptions.html#WindowsError" title="WindowsError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">WindowsError</span></code></a>, <code class="xref py py-exc docutils literal notranslate"><span class="pre">mmap.error</span></code>, <a class="reference internal" href="../library/socket.html#socket.error" title="socket.error"><code class="xref py py-exc docutils literal notranslate"><span class="pre">socket.error</span></code></a> or

  561. <a class="reference internal" href="../library/select.html#select.error" title="select.error"><code class="xref py py-exc docutils literal notranslate"><span class="pre">select.error</span></code></a>.  All these exception types are now only one:

  562. <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>.  The other names are kept as aliases for compatibility

  563. reasons.</p>

  564. <p>Also, it is now easier to catch a specific error condition.  Instead of

  565. inspecting the <code class="docutils literal notranslate"><span class="pre">errno</span></code> attribute (or <code class="docutils literal notranslate"><span class="pre">args[0]</span></code>) for a particular

  566. constant from the <a class="reference internal" href="../library/errno.html#module-errno" title="errno: Standard errno system symbols."><code class="xref py py-mod docutils literal notranslate"><span class="pre">errno</span></code></a> module, you can catch the adequate

  567. <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> subclass.  The available subclasses are the following:</p>

  568. <ul class="simple">

  569. <li><p><a class="reference internal" href="../library/exceptions.html#BlockingIOError" title="BlockingIOError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">BlockingIOError</span></code></a></p></li>

  570. <li><p><a class="reference internal" href="../library/exceptions.html#ChildProcessError" title="ChildProcessError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ChildProcessError</span></code></a></p></li>

  571. <li><p><a class="reference internal" href="../library/exceptions.html#ConnectionError" title="ConnectionError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ConnectionError</span></code></a></p></li>

  572. <li><p><a class="reference internal" href="../library/exceptions.html#FileExistsError" title="FileExistsError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">FileExistsError</span></code></a></p></li>

  573. <li><p><a class="reference internal" href="../library/exceptions.html#FileNotFoundError" title="FileNotFoundError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">FileNotFoundError</span></code></a></p></li>

  574. <li><p><a class="reference internal" href="../library/exceptions.html#InterruptedError" title="InterruptedError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">InterruptedError</span></code></a></p></li>

  575. <li><p><a class="reference internal" href="../library/exceptions.html#IsADirectoryError" title="IsADirectoryError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">IsADirectoryError</span></code></a></p></li>

  576. <li><p><a class="reference internal" href="../library/exceptions.html#NotADirectoryError" title="NotADirectoryError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">NotADirectoryError</span></code></a></p></li>

  577. <li><p><a class="reference internal" href="../library/exceptions.html#PermissionError" title="PermissionError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">PermissionError</span></code></a></p></li>

  578. <li><p><a class="reference internal" href="../library/exceptions.html#ProcessLookupError" title="ProcessLookupError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ProcessLookupError</span></code></a></p></li>

  579. <li><p><a class="reference internal" href="../library/exceptions.html#TimeoutError" title="TimeoutError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TimeoutError</span></code></a></p></li>

  580. </ul>

  581. <p>And the <a class="reference internal" href="../library/exceptions.html#ConnectionError" title="ConnectionError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ConnectionError</span></code></a> itself has finer-grained subclasses:</p>

  582. <ul class="simple">

  583. <li><p><a class="reference internal" href="../library/exceptions.html#BrokenPipeError" title="BrokenPipeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">BrokenPipeError</span></code></a></p></li>

  584. <li><p><a class="reference internal" href="../library/exceptions.html#ConnectionAbortedError" title="ConnectionAbortedError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ConnectionAbortedError</span></code></a></p></li>

  585. <li><p><a class="reference internal" href="../library/exceptions.html#ConnectionRefusedError" title="ConnectionRefusedError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ConnectionRefusedError</span></code></a></p></li>

  586. <li><p><a class="reference internal" href="../library/exceptions.html#ConnectionResetError" title="ConnectionResetError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ConnectionResetError</span></code></a></p></li>

  587. </ul>

  588. <p>Thanks to the new exceptions, common usages of the <a class="reference internal" href="../library/errno.html#module-errno" title="errno: Standard errno system symbols."><code class="xref py py-mod docutils literal notranslate"><span class="pre">errno</span></code></a> can now be

  589. avoided.  For example, the following code written for Python 3.2:</p>

  590. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">errno</span> <span class="kn">import</span> <span class="n">ENOENT</span><span class="p">,</span> <span class="n">EACCES</span><span class="p">,</span> <span class="n">EPERM</span>

  591. 

  592. <span class="k">try</span><span class="p">:</span>

  593.     <span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s2">&quot;document.txt&quot;</span><span class="p">)</span> <span class="k">as</span> <span class="n">f</span><span class="p">:</span>

  594.         <span class="n">content</span> <span class="o">=</span> <span class="n">f</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>

  595. <span class="k">except</span> <span class="ne">IOError</span> <span class="k">as</span> <span class="n">err</span><span class="p">:</span>

  596.     <span class="k">if</span> <span class="n">err</span><span class="o">.</span><span class="n">errno</span> <span class="o">==</span> <span class="n">ENOENT</span><span class="p">:</span>

  597.         <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;document.txt file is missing&quot;</span><span class="p">)</span>

  598.     <span class="k">elif</span> <span class="n">err</span><span class="o">.</span><span class="n">errno</span> <span class="ow">in</span> <span class="p">(</span><span class="n">EACCES</span><span class="p">,</span> <span class="n">EPERM</span><span class="p">):</span>

  599.         <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;You are not allowed to read document.txt&quot;</span><span class="p">)</span>

  600.     <span class="k">else</span><span class="p">:</span>

  601.         <span class="k">raise</span>

  602. </pre></div>

  603. </div>

  604. <p>can now be written without the <a class="reference internal" href="../library/errno.html#module-errno" title="errno: Standard errno system symbols."><code class="xref py py-mod docutils literal notranslate"><span class="pre">errno</span></code></a> import and without manual

  605. inspection of exception attributes:</p>

  606. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">try</span><span class="p">:</span>

  607.     <span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="s2">&quot;document.txt&quot;</span><span class="p">)</span> <span class="k">as</span> <span class="n">f</span><span class="p">:</span>

  608.         <span class="n">content</span> <span class="o">=</span> <span class="n">f</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>

  609. <span class="k">except</span> <span class="ne">FileNotFoundError</span><span class="p">:</span>

  610.     <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;document.txt file is missing&quot;</span><span class="p">)</span>

  611. <span class="k">except</span> <span class="ne">PermissionError</span><span class="p">:</span>

  612.     <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;You are not allowed to read document.txt&quot;</span><span class="p">)</span>

  613. </pre></div>

  614. </div>

  615. <div class="admonition seealso">

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

  617. <dl class="simple">

  618. <dt><span class="target" id="index-10"></span><a class="pep reference external" href="https://peps.python.org/pep-3151/"><strong>PEP 3151</strong></a> - Reworking the OS and IO Exception Hierarchy</dt><dd><p>PEP written and implemented by Antoine Pitrou</p>

  619. </dd>

  620. </dl>

  621. </div>

  622. </section>

  623. <section id="pep-380-syntax-for-delegating-to-a-subgenerator">

  624. <span id="pep-380"></span><span id="index-11"></span><h2>PEP 380: Syntax for Delegating to a Subgenerator<a class="headerlink" href="#pep-380-syntax-for-delegating-to-a-subgenerator" title="Link to this heading">¶</a></h2>

  625. <p>PEP 380 adds the <code class="docutils literal notranslate"><span class="pre">yield</span> <span class="pre">from</span></code> expression, allowing a <a class="reference internal" href="../glossary.html#term-generator"><span class="xref std std-term">generator</span></a> to

  626. delegate

  627. part of its operations to another generator. This allows a section of code

  628. containing <a class="reference internal" href="../reference/simple_stmts.html#yield"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">yield</span></code></a> to be factored out and placed in another generator.

  629. Additionally, the subgenerator is allowed to return with a value, and the

  630. value is made available to the delegating generator.</p>

  631. <p>While designed primarily for use in delegating to a subgenerator, the <code class="docutils literal notranslate"><span class="pre">yield</span>

  632. <span class="pre">from</span></code> expression actually allows delegation to arbitrary subiterators.</p>

  633. <p>For simple iterators, <code class="docutils literal notranslate"><span class="pre">yield</span> <span class="pre">from</span> <span class="pre">iterable</span></code> is essentially just a shortened

  634. form of <code class="docutils literal notranslate"><span class="pre">for</span> <span class="pre">item</span> <span class="pre">in</span> <span class="pre">iterable:</span> <span class="pre">yield</span> <span class="pre">item</span></code>:</p>

  635. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">g</span><span class="p">(</span><span class="n">x</span><span class="p">):</span>

  636. <span class="gp">... </span>    <span class="k">yield from</span> <span class="nb">range</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="o">-</span><span class="mi">1</span><span class="p">)</span>

  637. <span class="gp">... </span>    <span class="k">yield from</span> <span class="nb">range</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>

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

  639. <span class="gp">&gt;&gt;&gt; </span><span class="nb">list</span><span class="p">(</span><span class="n">g</span><span class="p">(</span><span class="mi">5</span><span class="p">))</span>

  640. <span class="go">[5, 4, 3, 2, 1, 0, 1, 2, 3, 4]</span>

  641. </pre></div>

  642. </div>

  643. <p>However, unlike an ordinary loop, <code class="docutils literal notranslate"><span class="pre">yield</span> <span class="pre">from</span></code> allows subgenerators to

  644. receive sent and thrown values directly from the calling scope, and

  645. return a final value to the outer generator:</p>

  646. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">accumulate</span><span class="p">():</span>

  647. <span class="gp">... </span>    <span class="n">tally</span> <span class="o">=</span> <span class="mi">0</span>

  648. <span class="gp">... </span>    <span class="k">while</span> <span class="mi">1</span><span class="p">:</span>

  649. <span class="gp">... </span>        <span class="nb">next</span> <span class="o">=</span> <span class="k">yield</span>

  650. <span class="gp">... </span>        <span class="k">if</span> <span class="nb">next</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>

  651. <span class="gp">... </span>            <span class="k">return</span> <span class="n">tally</span>

  652. <span class="gp">... </span>        <span class="n">tally</span> <span class="o">+=</span> <span class="nb">next</span>

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

  654. <span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">gather_tallies</span><span class="p">(</span><span class="n">tallies</span><span class="p">):</span>

  655. <span class="gp">... </span>    <span class="k">while</span> <span class="mi">1</span><span class="p">:</span>

  656. <span class="gp">... </span>        <span class="n">tally</span> <span class="o">=</span> <span class="k">yield from</span> <span class="n">accumulate</span><span class="p">()</span>

  657. <span class="gp">... </span>        <span class="n">tallies</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">tally</span><span class="p">)</span>

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

  659. <span class="gp">&gt;&gt;&gt; </span><span class="n">tallies</span> <span class="o">=</span> <span class="p">[]</span>

  660. <span class="gp">&gt;&gt;&gt; </span><span class="n">acc</span> <span class="o">=</span> <span class="n">gather_tallies</span><span class="p">(</span><span class="n">tallies</span><span class="p">)</span>

  661. <span class="gp">&gt;&gt;&gt; </span><span class="nb">next</span><span class="p">(</span><span class="n">acc</span><span class="p">)</span>  <span class="c1"># Ensure the accumulator is ready to accept values</span>

  662. <span class="gp">&gt;&gt;&gt; </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">4</span><span class="p">):</span>

  663. <span class="gp">... </span>    <span class="n">acc</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">i</span><span class="p">)</span>

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

  665. <span class="gp">&gt;&gt;&gt; </span><span class="n">acc</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="kc">None</span><span class="p">)</span>  <span class="c1"># Finish the first tally</span>

  666. <span class="gp">&gt;&gt;&gt; </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">5</span><span class="p">):</span>

  667. <span class="gp">... </span>    <span class="n">acc</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">i</span><span class="p">)</span>

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

  669. <span class="gp">&gt;&gt;&gt; </span><span class="n">acc</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="kc">None</span><span class="p">)</span>  <span class="c1"># Finish the second tally</span>

  670. <span class="gp">&gt;&gt;&gt; </span><span class="n">tallies</span>

  671. <span class="go">[6, 10]</span>

  672. </pre></div>

  673. </div>

  674. <p>The main principle driving this change is to allow even generators that are

  675. designed to be used with the <code class="docutils literal notranslate"><span class="pre">send</span></code> and <code class="docutils literal notranslate"><span class="pre">throw</span></code> methods to be split into

  676. multiple subgenerators as easily as a single large function can be split into

  677. multiple subfunctions.</p>

  678. <div class="admonition seealso">

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

  680. <dl class="simple">

  681. <dt><span class="target" id="index-12"></span><a class="pep reference external" href="https://peps.python.org/pep-0380/"><strong>PEP 380</strong></a> - Syntax for Delegating to a Subgenerator</dt><dd><p>PEP written by Greg Ewing; implementation by Greg Ewing, integrated into

  682. 3.3 by Renaud Blanch, Ryan Kelly and Nick Coghlan; documentation by

  683. Zbigniew Jędrzejewski-Szmek and Nick Coghlan</p>

  684. </dd>

  685. </dl>

  686. </div>

  687. </section>

  688. <section id="pep-409-suppressing-exception-context">

  689. <h2>PEP 409: Suppressing exception context<a class="headerlink" href="#pep-409-suppressing-exception-context" title="Link to this heading">¶</a></h2>

  690. <p>PEP 409 introduces new syntax that allows the display of the chained

  691. exception context to be disabled. This allows cleaner error messages in

  692. applications that convert between exception types:</p>

  693. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">D</span><span class="p">:</span>

  694. <span class="gp">... </span>    <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">extra</span><span class="p">):</span>

  695. <span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">_extra_attributes</span> <span class="o">=</span> <span class="n">extra</span>

  696. <span class="gp">... </span>    <span class="k">def</span> <span class="fm">__getattr__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">attr</span><span class="p">):</span>

  697. <span class="gp">... </span>        <span class="k">try</span><span class="p">:</span>

  698. <span class="gp">... </span>            <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">_extra_attributes</span><span class="p">[</span><span class="n">attr</span><span class="p">]</span>

  699. <span class="gp">... </span>        <span class="k">except</span> <span class="ne">KeyError</span><span class="p">:</span>

  700. <span class="gp">... </span>            <span class="k">raise</span> <span class="ne">AttributeError</span><span class="p">(</span><span class="n">attr</span><span class="p">)</span> <span class="kn">from</span> <span class="kc">None</span>

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

  702. <span class="gp">&gt;&gt;&gt; </span><span class="n">D</span><span class="p">({})</span><span class="o">.</span><span class="n">x</span>

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

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

  705.   File <span class="nb">&quot;&lt;stdin&gt;&quot;</span>, line <span class="m">8</span>, in <span class="n">__getattr__</span>

  706. <span class="gr">AttributeError</span>: <span class="n">x</span>

  707. </pre></div>

  708. </div>

  709. <p>Without the <code class="docutils literal notranslate"><span class="pre">from</span> <span class="pre">None</span></code> suffix to suppress the cause, the original

  710. exception would be displayed by default:</p>

  711. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">C</span><span class="p">:</span>

  712. <span class="gp">... </span>    <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">extra</span><span class="p">):</span>

  713. <span class="gp">... </span>        <span class="bp">self</span><span class="o">.</span><span class="n">_extra_attributes</span> <span class="o">=</span> <span class="n">extra</span>

  714. <span class="gp">... </span>    <span class="k">def</span> <span class="fm">__getattr__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">attr</span><span class="p">):</span>

  715. <span class="gp">... </span>        <span class="k">try</span><span class="p">:</span>

  716. <span class="gp">... </span>            <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">_extra_attributes</span><span class="p">[</span><span class="n">attr</span><span class="p">]</span>

  717. <span class="gp">... </span>        <span class="k">except</span> <span class="ne">KeyError</span><span class="p">:</span>

  718. <span class="gp">... </span>            <span class="k">raise</span> <span class="ne">AttributeError</span><span class="p">(</span><span class="n">attr</span><span class="p">)</span>

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

  720. <span class="gp">&gt;&gt;&gt; </span><span class="n">C</span><span class="p">({})</span><span class="o">.</span><span class="n">x</span>

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

  722.   File <span class="nb">&quot;&lt;stdin&gt;&quot;</span>, line <span class="m">6</span>, in <span class="n">__getattr__</span>

  723. <span class="gr">KeyError</span>: <span class="n">&#39;x&#39;</span>

  724. 

  725. <span class="gt">During handling of the above exception, another exception occurred:</span>

  726. 

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

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

  729.   File <span class="nb">&quot;&lt;stdin&gt;&quot;</span>, line <span class="m">8</span>, in <span class="n">__getattr__</span>

  730. <span class="gr">AttributeError</span>: <span class="n">x</span>

  731. </pre></div>

  732. </div>

  733. <p>No debugging capability is lost, as the original exception context remains

  734. available if needed (for example, if an intervening library has incorrectly

  735. suppressed valuable underlying details):</p>

  736. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">try</span><span class="p">:</span>

  737. <span class="gp">... </span>    <span class="n">D</span><span class="p">({})</span><span class="o">.</span><span class="n">x</span>

  738. <span class="gp">... </span><span class="k">except</span> <span class="ne">AttributeError</span> <span class="k">as</span> <span class="n">exc</span><span class="p">:</span>

  739. <span class="gp">... </span>    <span class="nb">print</span><span class="p">(</span><span class="nb">repr</span><span class="p">(</span><span class="n">exc</span><span class="o">.</span><span class="n">__context__</span><span class="p">))</span>

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

  741. <span class="go">KeyError(&#39;x&#39;,)</span>

  742. </pre></div>

  743. </div>

  744. <div class="admonition seealso">

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

  746. <dl class="simple">

  747. <dt><span class="target" id="index-13"></span><a class="pep reference external" href="https://peps.python.org/pep-0409/"><strong>PEP 409</strong></a> - Suppressing exception context</dt><dd><p>PEP written by Ethan Furman; implemented by Ethan Furman and Nick

  748. Coghlan.</p>

  749. </dd>

  750. </dl>

  751. </div>

  752. </section>

  753. <section id="pep-414-explicit-unicode-literals">

  754. <h2>PEP 414: Explicit Unicode literals<a class="headerlink" href="#pep-414-explicit-unicode-literals" title="Link to this heading">¶</a></h2>

  755. <p>To ease the transition from Python 2 for Unicode aware Python applications

  756. that make heavy use of Unicode literals, Python 3.3 once again supports the

  757. “<code class="docutils literal notranslate"><span class="pre">u</span></code>” prefix for string literals. This prefix has no semantic significance

  758. in Python 3, it is provided solely to reduce the number of purely mechanical

  759. changes in migrating to Python 3, making it easier for developers to focus on

  760. the more significant semantic changes (such as the stricter default

  761. separation of binary and text data).</p>

  762. <div class="admonition seealso">

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

  764. <dl class="simple">

  765. <dt><span class="target" id="index-14"></span><a class="pep reference external" href="https://peps.python.org/pep-0414/"><strong>PEP 414</strong></a> - Explicit Unicode literals</dt><dd><p>PEP written by Armin Ronacher.</p>

  766. </dd>

  767. </dl>

  768. </div>

  769. </section>

  770. <section id="pep-3155-qualified-name-for-classes-and-functions">

  771. <h2>PEP 3155: Qualified name for classes and functions<a class="headerlink" href="#pep-3155-qualified-name-for-classes-and-functions" title="Link to this heading">¶</a></h2>

  772. <p>Functions and class objects have a new <code class="docutils literal notranslate"><span class="pre">__qualname__</span></code> attribute representing

  773. the “path” from the module top-level to their definition.  For global functions

  774. and classes, this is the same as <code class="docutils literal notranslate"><span class="pre">__name__</span></code>.  For other functions and classes,

  775. it provides better information about where they were actually defined, and

  776. how they might be accessible from the global scope.</p>

  777. <p>Example with (non-bound) methods:</p>

  778. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">C</span><span class="p">:</span>

  779. <span class="gp">... </span>    <span class="k">def</span> <span class="nf">meth</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>

  780. <span class="gp">... </span>        <span class="k">pass</span>

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

  782. <span class="gp">&gt;&gt;&gt; </span><span class="n">C</span><span class="o">.</span><span class="n">meth</span><span class="o">.</span><span class="vm">__name__</span>

  783. <span class="go">&#39;meth&#39;</span>

  784. <span class="gp">&gt;&gt;&gt; </span><span class="n">C</span><span class="o">.</span><span class="n">meth</span><span class="o">.</span><span class="vm">__qualname__</span>

  785. <span class="go">&#39;C.meth&#39;</span>

  786. </pre></div>

  787. </div>

  788. <p>Example with nested classes:</p>

  789. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">C</span><span class="p">:</span>

  790. <span class="gp">... </span>    <span class="k">class</span> <span class="nc">D</span><span class="p">:</span>

  791. <span class="gp">... </span>        <span class="k">def</span> <span class="nf">meth</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>

  792. <span class="gp">... </span>            <span class="k">pass</span>

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

  794. <span class="gp">&gt;&gt;&gt; </span><span class="n">C</span><span class="o">.</span><span class="n">D</span><span class="o">.</span><span class="vm">__name__</span>

  795. <span class="go">&#39;D&#39;</span>

  796. <span class="gp">&gt;&gt;&gt; </span><span class="n">C</span><span class="o">.</span><span class="n">D</span><span class="o">.</span><span class="vm">__qualname__</span>

  797. <span class="go">&#39;C.D&#39;</span>

  798. <span class="gp">&gt;&gt;&gt; </span><span class="n">C</span><span class="o">.</span><span class="n">D</span><span class="o">.</span><span class="n">meth</span><span class="o">.</span><span class="vm">__name__</span>

  799. <span class="go">&#39;meth&#39;</span>

  800. <span class="gp">&gt;&gt;&gt; </span><span class="n">C</span><span class="o">.</span><span class="n">D</span><span class="o">.</span><span class="n">meth</span><span class="o">.</span><span class="vm">__qualname__</span>

  801. <span class="go">&#39;C.D.meth&#39;</span>

  802. </pre></div>

  803. </div>

  804. <p>Example with nested functions:</p>

  805. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">outer</span><span class="p">():</span>

  806. <span class="gp">... </span>    <span class="k">def</span> <span class="nf">inner</span><span class="p">():</span>

  807. <span class="gp">... </span>        <span class="k">pass</span>

  808. <span class="gp">... </span>    <span class="k">return</span> <span class="n">inner</span>

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

  810. <span class="gp">&gt;&gt;&gt; </span><span class="n">outer</span><span class="p">()</span><span class="o">.</span><span class="vm">__name__</span>

  811. <span class="go">&#39;inner&#39;</span>

  812. <span class="gp">&gt;&gt;&gt; </span><span class="n">outer</span><span class="p">()</span><span class="o">.</span><span class="vm">__qualname__</span>

  813. <span class="go">&#39;outer.&lt;locals&gt;.inner&#39;</span>

  814. </pre></div>

  815. </div>

  816. <p>The string representation of those objects is also changed to include the

  817. new, more precise information:</p>

  818. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="nb">str</span><span class="p">(</span><span class="n">C</span><span class="o">.</span><span class="n">D</span><span class="p">)</span>

  819. <span class="go">&quot;&lt;class &#39;__main__.C.D&#39;&gt;&quot;</span>

  820. <span class="gp">&gt;&gt;&gt; </span><span class="nb">str</span><span class="p">(</span><span class="n">C</span><span class="o">.</span><span class="n">D</span><span class="o">.</span><span class="n">meth</span><span class="p">)</span>

  821. <span class="go">&#39;&lt;function C.D.meth at 0x7f46b9fe31e0&gt;&#39;</span>

  822. </pre></div>

  823. </div>

  824. <div class="admonition seealso">

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

  826. <dl class="simple">

  827. <dt><span class="target" id="index-15"></span><a class="pep reference external" href="https://peps.python.org/pep-3155/"><strong>PEP 3155</strong></a> - Qualified name for classes and functions</dt><dd><p>PEP written and implemented by Antoine Pitrou.</p>

  828. </dd>

  829. </dl>

  830. </div>

  831. </section>

  832. <section id="pep-412-key-sharing-dictionary">

  833. <span id="pep-412"></span><h2>PEP 412: Key-Sharing Dictionary<a class="headerlink" href="#pep-412-key-sharing-dictionary" title="Link to this heading">¶</a></h2>

  834. <p>Dictionaries used for the storage of objects’ attributes are now able to

  835. share part of their internal storage between each other (namely, the part

  836. which stores the keys and their respective hashes).  This reduces the memory

  837. consumption of programs creating many instances of non-builtin types.</p>

  838. <div class="admonition seealso">

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

  840. <dl class="simple">

  841. <dt><span class="target" id="index-16"></span><a class="pep reference external" href="https://peps.python.org/pep-0412/"><strong>PEP 412</strong></a> - Key-Sharing Dictionary</dt><dd><p>PEP written and implemented by Mark Shannon.</p>

  842. </dd>

  843. </dl>

  844. </div>

  845. </section>

  846. <section id="pep-362-function-signature-object">

  847. <h2>PEP 362: Function Signature Object<a class="headerlink" href="#pep-362-function-signature-object" title="Link to this heading">¶</a></h2>

  848. <p>A new function <a class="reference internal" href="../library/inspect.html#inspect.signature" title="inspect.signature"><code class="xref py py-func docutils literal notranslate"><span class="pre">inspect.signature()</span></code></a> makes introspection of python

  849. callables easy and straightforward.  A broad range of callables is supported:

  850. python functions, decorated or not, classes, and <a class="reference internal" href="../library/functools.html#functools.partial" title="functools.partial"><code class="xref py py-func docutils literal notranslate"><span class="pre">functools.partial()</span></code></a>

  851. objects.  New classes <a class="reference internal" href="../library/inspect.html#inspect.Signature" title="inspect.Signature"><code class="xref py py-class docutils literal notranslate"><span class="pre">inspect.Signature</span></code></a>, <a class="reference internal" href="../library/inspect.html#inspect.Parameter" title="inspect.Parameter"><code class="xref py py-class docutils literal notranslate"><span class="pre">inspect.Parameter</span></code></a>

  852. and <a class="reference internal" href="../library/inspect.html#inspect.BoundArguments" title="inspect.BoundArguments"><code class="xref py py-class docutils literal notranslate"><span class="pre">inspect.BoundArguments</span></code></a> hold information about the call signatures,

  853. such as, annotations, default values, parameters kinds, and bound arguments,

  854. which considerably simplifies writing decorators and any code that validates

  855. or amends calling signatures or arguments.</p>

  856. <div class="admonition seealso">

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

  858. <dl class="simple">

  859. <dt><span class="target" id="index-17"></span><a class="pep reference external" href="https://peps.python.org/pep-0362/"><strong>PEP 362</strong></a>: -  Function Signature Object</dt><dd><p>PEP written by Brett Cannon, Yury Selivanov, Larry Hastings, Jiwon Seo;

  860. implemented by Yury Selivanov.</p>

  861. </dd>

  862. </dl>

  863. </div>

  864. </section>

  865. <section id="pep-421-adding-sys-implementation">

  866. <h2>PEP 421: Adding sys.implementation<a class="headerlink" href="#pep-421-adding-sys-implementation" title="Link to this heading">¶</a></h2>

  867. <p>A new attribute on the <a class="reference internal" href="../library/sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a> module exposes details specific to the

  868. implementation of the currently running interpreter.  The initial set of

  869. attributes on <a class="reference internal" href="../library/sys.html#sys.implementation" title="sys.implementation"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.implementation</span></code></a> are <code class="docutils literal notranslate"><span class="pre">name</span></code>, <code class="docutils literal notranslate"><span class="pre">version</span></code>,

  870. <code class="docutils literal notranslate"><span class="pre">hexversion</span></code>, and <code class="docutils literal notranslate"><span class="pre">cache_tag</span></code>.</p>

  871. <p>The intention of <code class="docutils literal notranslate"><span class="pre">sys.implementation</span></code> is to consolidate into one namespace

  872. the implementation-specific data used by the standard library.  This allows

  873. different Python implementations to share a single standard library code base

  874. much more easily.  In its initial state, <code class="docutils literal notranslate"><span class="pre">sys.implementation</span></code> holds only a

  875. small portion of the implementation-specific data.  Over time that ratio will

  876. shift in order to make the standard library more portable.</p>

  877. <p>One example of improved standard library portability is <code class="docutils literal notranslate"><span class="pre">cache_tag</span></code>.  As of

  878. Python 3.3, <code class="docutils literal notranslate"><span class="pre">sys.implementation.cache_tag</span></code> is used by <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> to

  879. support <span class="target" id="index-18"></span><a class="pep reference external" href="https://peps.python.org/pep-3147/"><strong>PEP 3147</strong></a> compliance.  Any Python implementation that uses

  880. <code class="docutils literal notranslate"><span class="pre">importlib</span></code> for its built-in import system may use <code class="docutils literal notranslate"><span class="pre">cache_tag</span></code> to control

  881. the caching behavior for modules.</p>

  882. <section id="simplenamespace">

  883. <h3>SimpleNamespace<a class="headerlink" href="#simplenamespace" title="Link to this heading">¶</a></h3>

  884. <p>The implementation of <code class="docutils literal notranslate"><span class="pre">sys.implementation</span></code> also introduces a new type to

  885. Python: <a class="reference internal" href="../library/types.html#types.SimpleNamespace" title="types.SimpleNamespace"><code class="xref py py-class docutils literal notranslate"><span class="pre">types.SimpleNamespace</span></code></a>.  In contrast to a mapping-based

  886. namespace, like <a class="reference internal" href="../library/stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a>, <code class="docutils literal notranslate"><span class="pre">SimpleNamespace</span></code> is attribute-based, like

  887. <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>.  However, unlike <code class="docutils literal notranslate"><span class="pre">object</span></code>, <code class="docutils literal notranslate"><span class="pre">SimpleNamespace</span></code> instances

  888. are writable.  This means that you can add, remove, and modify the namespace

  889. through normal attribute access.</p>

  890. <div class="admonition seealso">

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

  892. <dl class="simple">

  893. <dt><span class="target" id="index-19"></span><a class="pep reference external" href="https://peps.python.org/pep-0421/"><strong>PEP 421</strong></a> - Adding sys.implementation</dt><dd><p>PEP written and implemented by Eric Snow.</p>

  894. </dd>

  895. </dl>

  896. </div>

  897. </section>

  898. </section>

  899. <section id="using-importlib-as-the-implementation-of-import">

  900. <span id="importlib"></span><h2>Using importlib as the Implementation of Import<a class="headerlink" href="#using-importlib-as-the-implementation-of-import" title="Link to this heading">¶</a></h2>

  901. <p><a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=2377">bpo-2377</a> - Replace __import__ w/ importlib.__import__

  902. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13959">bpo-13959</a> - Re-implement parts of <code class="xref py py-mod docutils literal notranslate"><span class="pre">imp</span></code> in pure Python

  903. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14605">bpo-14605</a> - Make import machinery explicit

  904. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14646">bpo-14646</a> - Require loaders set __loader__ and __package__</p>

  905. <p>The <a class="reference internal" href="../library/functions.html#import__" title="__import__"><code class="xref py py-func docutils literal notranslate"><span class="pre">__import__()</span></code></a> function is now powered by <a class="reference internal" href="../library/importlib.html#importlib.__import__" title="importlib.__import__"><code class="xref py py-func docutils literal notranslate"><span class="pre">importlib.__import__()</span></code></a>.

  906. This work leads to the completion of “phase 2” of <span class="target" id="index-20"></span><a class="pep reference external" href="https://peps.python.org/pep-0302/"><strong>PEP 302</strong></a>. There are

  907. multiple benefits to this change. First, it has allowed for more of the

  908. machinery powering import to be exposed instead of being implicit and hidden

  909. within the C code. It also provides a single implementation for all Python VMs

  910. supporting Python 3.3 to use, helping to end any VM-specific deviations in

  911. import semantics. And finally it eases the maintenance of import, allowing for

  912. future growth to occur.</p>

  913. <p>For the common user, there should be no visible change in semantics.  For

  914. those whose code currently manipulates import or calls import

  915. programmatically, the code changes that might possibly be required are covered

  916. in the <a class="reference internal" href="#porting-python-code">Porting Python code</a> section of this document.</p>

  917. <section id="new-apis">

  918. <h3>New APIs<a class="headerlink" href="#new-apis" title="Link to this heading">¶</a></h3>

  919. <p>One of the large benefits of this work is the exposure of what goes into

  920. making the import statement work. That means the various importers that were

  921. once implicit are now fully exposed as part 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> package.</p>

  922. <p>The abstract base classes defined in <a class="reference internal" href="../library/importlib.html#module-importlib.abc" title="importlib.abc: Abstract base classes related to import"><code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib.abc</span></code></a> have been expanded

  923. to properly delineate between <a class="reference internal" href="../glossary.html#term-meta-path-finder"><span class="xref std std-term">meta path finders</span></a>

  924. and <a class="reference internal" href="../glossary.html#term-path-entry-finder"><span class="xref std std-term">path entry finders</span></a> by introducing

  925. <a class="reference internal" href="../library/importlib.html#importlib.abc.MetaPathFinder" title="importlib.abc.MetaPathFinder"><code class="xref py py-class docutils literal notranslate"><span class="pre">importlib.abc.MetaPathFinder</span></code></a> and

  926. <a class="reference internal" href="../library/importlib.html#importlib.abc.PathEntryFinder" title="importlib.abc.PathEntryFinder"><code class="xref py py-class docutils literal notranslate"><span class="pre">importlib.abc.PathEntryFinder</span></code></a>, respectively. The old ABC of

  927. <code class="xref py py-class docutils literal notranslate"><span class="pre">importlib.abc.Finder</span></code> is now only provided for backwards-compatibility

  928. and does not enforce any method requirements.</p>

  929. <p>In terms of finders, <a class="reference internal" href="../library/importlib.html#importlib.machinery.FileFinder" title="importlib.machinery.FileFinder"><code class="xref py py-class docutils literal notranslate"><span class="pre">importlib.machinery.FileFinder</span></code></a> exposes the

  930. mechanism used to search for source and bytecode files of a module. Previously

  931. this class was an implicit member of <a class="reference internal" href="../library/sys.html#sys.path_hooks" title="sys.path_hooks"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path_hooks</span></code></a>.</p>

  932. <p>For loaders, the new abstract base class <a class="reference internal" href="../library/importlib.html#importlib.abc.FileLoader" title="importlib.abc.FileLoader"><code class="xref py py-class docutils literal notranslate"><span class="pre">importlib.abc.FileLoader</span></code></a> helps

  933. write a loader that uses the file system as the storage mechanism for a module’s

  934. code. The loader for source files

  935. (<a class="reference internal" href="../library/importlib.html#importlib.machinery.SourceFileLoader" title="importlib.machinery.SourceFileLoader"><code class="xref py py-class docutils literal notranslate"><span class="pre">importlib.machinery.SourceFileLoader</span></code></a>), sourceless bytecode files

  936. (<a class="reference internal" href="../library/importlib.html#importlib.machinery.SourcelessFileLoader" title="importlib.machinery.SourcelessFileLoader"><code class="xref py py-class docutils literal notranslate"><span class="pre">importlib.machinery.SourcelessFileLoader</span></code></a>), and extension modules

  937. (<a class="reference internal" href="../library/importlib.html#importlib.machinery.ExtensionFileLoader" title="importlib.machinery.ExtensionFileLoader"><code class="xref py py-class docutils literal notranslate"><span class="pre">importlib.machinery.ExtensionFileLoader</span></code></a>) are now available for

  938. direct use.</p>

  939. <p><a class="reference internal" href="../library/exceptions.html#ImportError" title="ImportError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ImportError</span></code></a> now has <code class="docutils literal notranslate"><span class="pre">name</span></code> and <code class="docutils literal notranslate"><span class="pre">path</span></code> attributes which are set when

  940. there is relevant data to provide. The message for failed imports will also

  941. provide the full name of the module now instead of just the tail end of the

  942. module’s name.</p>

  943. <p>The <a class="reference internal" href="../library/importlib.html#importlib.invalidate_caches" title="importlib.invalidate_caches"><code class="xref py py-func docutils literal notranslate"><span class="pre">importlib.invalidate_caches()</span></code></a> function will now call the method with

  944. the same name on all finders cached in <a class="reference internal" href="../library/sys.html#sys.path_importer_cache" title="sys.path_importer_cache"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path_importer_cache</span></code></a> to help

  945. clean up any stored state as necessary.</p>

  946. </section>

  947. <section id="visible-changes">

  948. <h3>Visible Changes<a class="headerlink" href="#visible-changes" title="Link to this heading">¶</a></h3>

  949. <p>For potential required changes to code, see the <a class="reference internal" href="#porting-python-code">Porting Python code</a>

  950. section.</p>

  951. <p>Beyond the expanse of what <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> now exposes, there are other

  952. visible changes to import. The biggest is that <a class="reference internal" href="../library/sys.html#sys.meta_path" title="sys.meta_path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.meta_path</span></code></a> and

  953. <a class="reference internal" href="../library/sys.html#sys.path_hooks" title="sys.path_hooks"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path_hooks</span></code></a> now store all of the meta path finders and path entry

  954. hooks used by import.  Previously the finders were implicit and hidden within

  955. the C code of import instead of being directly exposed. This means that one can

  956. now easily remove or change the order of the various finders to fit one’s needs.</p>

  957. <p>Another change is that all modules have a <code class="docutils literal notranslate"><span class="pre">__loader__</span></code> attribute, storing the

  958. loader used to create the module. <span class="target" id="index-21"></span><a class="pep reference external" href="https://peps.python.org/pep-0302/"><strong>PEP 302</strong></a> has been updated to make this

  959. attribute mandatory for loaders to implement, so in the future once 3rd-party

  960. loaders have been updated people will be able to rely on the existence of the

  961. attribute. Until such time, though, import is setting the module post-load.</p>

  962. <p>Loaders are also now expected to set the <code class="docutils literal notranslate"><span class="pre">__package__</span></code> attribute from

  963. <span class="target" id="index-22"></span><a class="pep reference external" href="https://peps.python.org/pep-0366/"><strong>PEP 366</strong></a>. Once again, import itself is already setting this on all loaders

  964. from <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> and import itself is setting the attribute post-load.</p>

  965. <p><code class="docutils literal notranslate"><span class="pre">None</span></code> is now inserted into <a class="reference internal" href="../library/sys.html#sys.path_importer_cache" title="sys.path_importer_cache"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path_importer_cache</span></code></a> when no finder

  966. can be found on <a class="reference internal" href="../library/sys.html#sys.path_hooks" title="sys.path_hooks"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path_hooks</span></code></a>. Since <code class="xref py py-class docutils literal notranslate"><span class="pre">imp.NullImporter</span></code> is not

  967. directly exposed on <a class="reference internal" href="../library/sys.html#sys.path_hooks" title="sys.path_hooks"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path_hooks</span></code></a> it could no longer be relied upon to

  968. always be available to use as a value representing no finder found.</p>

  969. <p>All other changes relate to semantic changes which should be taken into

  970. consideration when updating code for Python 3.3, and thus should be read about

  971. in the <a class="reference internal" href="#porting-python-code">Porting Python code</a> section of this document.</p>

  972. <p>(Implementation by Brett Cannon)</p>

  973. </section>

  974. </section>

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

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

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

  978. <ul>

  979. <li><p>Added support for Unicode name aliases and named sequences.

  980. Both <a class="reference internal" href="../library/unicodedata.html#unicodedata.lookup" title="unicodedata.lookup"><code class="xref py py-func docutils literal notranslate"><span class="pre">unicodedata.lookup()</span></code></a> and <code class="docutils literal notranslate"><span class="pre">'\N{...}'</span></code> now resolve name aliases,

  981. and <a class="reference internal" href="../library/unicodedata.html#unicodedata.lookup" title="unicodedata.lookup"><code class="xref py py-func docutils literal notranslate"><span class="pre">unicodedata.lookup()</span></code></a> resolves named sequences too.</p>

  982. <p>(Contributed by Ezio Melotti in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12753">bpo-12753</a>.)</p>

  983. </li>

  984. <li><p>Unicode database updated to UCD version 6.1.0</p></li>

  985. <li><p>Equality comparisons on <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> objects now return a result reflecting

  986. the equality of the underlying sequences generated by those range objects.

  987. (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13201">bpo-13201</a>)</p></li>

  988. <li><p>The <code class="docutils literal notranslate"><span class="pre">count()</span></code>, <code class="docutils literal notranslate"><span class="pre">find()</span></code>, <code class="docutils literal notranslate"><span class="pre">rfind()</span></code>, <code class="docutils literal notranslate"><span class="pre">index()</span></code> and <code class="docutils literal notranslate"><span class="pre">rindex()</span></code>

  989. methods of <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> 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 accept an

  990. integer between 0 and 255 as their first argument.</p>

  991. <p>(Contributed by Petri Lehtinen in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12170">bpo-12170</a>.)</p>

  992. </li>

  993. <li><p>The <code class="docutils literal notranslate"><span class="pre">rjust()</span></code>, <code class="docutils literal notranslate"><span class="pre">ljust()</span></code>, and <code class="docutils literal notranslate"><span class="pre">center()</span></code> methods of <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>

  994. 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> now accept a <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> for the <code class="docutils literal notranslate"><span class="pre">fill</span></code>

  995. argument.  (Contributed by Petri Lehtinen in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12380">bpo-12380</a>.)</p></li>

  996. <li><p>New methods have been added to <a class="reference internal" href="../library/stdtypes.html#list" title="list"><code class="xref py py-class docutils literal notranslate"><span class="pre">list</span></code></a> 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>:

  997. <code class="docutils literal notranslate"><span class="pre">copy()</span></code> and <code class="docutils literal notranslate"><span class="pre">clear()</span></code> (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10516">bpo-10516</a>).  Consequently,

  998. <a class="reference internal" href="../library/collections.abc.html#collections.abc.MutableSequence" title="collections.abc.MutableSequence"><code class="xref py py-class docutils literal notranslate"><span class="pre">MutableSequence</span></code></a> now also defines a

  999. <code class="xref py py-meth docutils literal notranslate"><span class="pre">clear()</span></code> method (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11388">bpo-11388</a>).</p></li>

  1000. <li><p>Raw bytes literals can now be written <code class="docutils literal notranslate"><span class="pre">rb&quot;...&quot;</span></code> as well as <code class="docutils literal notranslate"><span class="pre">br&quot;...&quot;</span></code>.</p>

  1001. <p>(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13748">bpo-13748</a>.)</p>

  1002. </li>

  1003. <li><p><a class="reference internal" href="../library/stdtypes.html#dict.setdefault" title="dict.setdefault"><code class="xref py py-meth docutils literal notranslate"><span class="pre">dict.setdefault()</span></code></a> now does only one lookup for the given key, making

  1004. it atomic when used with built-in types.</p>

  1005. <p>(Contributed by Filip Gruszczyński in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13521">bpo-13521</a>.)</p>

  1006. </li>

  1007. <li><p>The error messages produced when a function call does not match the function

  1008. signature have been significantly improved.</p>

  1009. <p>(Contributed by Benjamin Peterson.)</p>

  1010. </li>

  1011. </ul>

  1012. </section>

  1013. <section id="a-finer-grained-import-lock">

  1014. <h2>A Finer-Grained Import Lock<a class="headerlink" href="#a-finer-grained-import-lock" title="Link to this heading">¶</a></h2>

  1015. <p>Previous versions of CPython have always relied on a global import lock.

  1016. This led to unexpected annoyances, such as deadlocks when importing a module

  1017. would trigger code execution in a different thread as a side-effect.

  1018. Clumsy workarounds were sometimes employed, such as the

  1019. <a class="reference internal" href="../c-api/import.html#c.PyImport_ImportModuleNoBlock" title="PyImport_ImportModuleNoBlock"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyImport_ImportModuleNoBlock()</span></code></a> C API function.</p>

  1020. <p>In Python 3.3, importing a module takes a per-module lock.  This correctly

  1021. serializes importation of a given module from multiple threads (preventing

  1022. the exposure of incompletely initialized modules), while eliminating the

  1023. aforementioned annoyances.</p>

  1024. <p>(Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=9260">bpo-9260</a>.)</p>

  1025. </section>

  1026. <section id="builtin-functions-and-types">

  1027. <h2>Builtin functions and types<a class="headerlink" href="#builtin-functions-and-types" title="Link to this heading">¶</a></h2>

  1028. <ul class="simple">

  1029. <li><p><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> gets a new <em>opener</em> parameter: the underlying file descriptor

  1030. for the file object is then obtained by calling <em>opener</em> with (<em>file</em>,

  1031. <em>flags</em>). It can be used to use custom flags like <a class="reference internal" href="../library/os.html#os.O_CLOEXEC" title="os.O_CLOEXEC"><code class="xref py py-const docutils literal notranslate"><span class="pre">os.O_CLOEXEC</span></code></a> for

  1032. example. The <code class="docutils literal notranslate"><span class="pre">'x'</span></code> mode was added: open for exclusive creation, failing if

  1033. the file already exists.</p></li>

  1034. <li><p><a class="reference internal" href="../library/functions.html#print" title="print"><code class="xref py py-func docutils literal notranslate"><span class="pre">print()</span></code></a>: added the <em>flush</em> keyword argument. If the <em>flush</em> keyword

  1035. argument is true, the stream is forcibly flushed.</p></li>

  1036. <li><p><a class="reference internal" href="../library/functions.html#hash" title="hash"><code class="xref py py-func docutils literal notranslate"><span class="pre">hash()</span></code></a>: hash randomization is enabled by default, see

  1037. <a class="reference internal" href="../reference/datamodel.html#object.__hash__" title="object.__hash__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">object.__hash__()</span></code></a> and <span class="target" id="index-23"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONHASHSEED"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHASHSEED</span></code></a>.</p></li>

  1038. <li><p>The <a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> type gets a new <a class="reference internal" href="../library/stdtypes.html#str.casefold" title="str.casefold"><code class="xref py py-meth docutils literal notranslate"><span class="pre">casefold()</span></code></a> method: return a

  1039. casefolded copy of the string, casefolded strings may be used for caseless

  1040. matching. For example, <code class="docutils literal notranslate"><span class="pre">'ß'.casefold()</span></code> returns <code class="docutils literal notranslate"><span class="pre">'ss'</span></code>.</p></li>

  1041. <li><p>The sequence documentation has been substantially rewritten to better

  1042. explain the binary/text sequence distinction and to provide specific

  1043. documentation sections for the individual builtin sequence types

  1044. (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4966">bpo-4966</a>).</p></li>

  1045. </ul>

  1046. </section>

  1047. <section id="new-modules">

  1048. <h2>New Modules<a class="headerlink" href="#new-modules" title="Link to this heading">¶</a></h2>

  1049. <section id="faulthandler">

  1050. <h3>faulthandler<a class="headerlink" href="#faulthandler" title="Link to this heading">¶</a></h3>

  1051. <p>This new debug module <a class="reference internal" href="../library/faulthandler.html#module-faulthandler" title="faulthandler: Dump the Python traceback."><code class="xref py py-mod docutils literal notranslate"><span class="pre">faulthandler</span></code></a> contains functions to dump Python tracebacks explicitly,

  1052. on a fault (a crash like a segmentation fault), after a timeout, or on a user

  1053. signal. Call <a class="reference internal" href="../library/faulthandler.html#faulthandler.enable" title="faulthandler.enable"><code class="xref py py-func docutils literal notranslate"><span class="pre">faulthandler.enable()</span></code></a> to install fault handlers for the

  1054. <code class="xref py py-const docutils literal notranslate"><span class="pre">SIGSEGV</span></code>, <code class="xref py py-const docutils literal notranslate"><span class="pre">SIGFPE</span></code>, <code class="xref py py-const docutils literal notranslate"><span class="pre">SIGABRT</span></code>, <code class="xref py py-const docutils literal notranslate"><span class="pre">SIGBUS</span></code>, and

  1055. <code class="xref py py-const docutils literal notranslate"><span class="pre">SIGILL</span></code> signals. You can also enable them at startup by setting the

  1056. <span class="target" id="index-24"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONFAULTHANDLER"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONFAULTHANDLER</span></code></a> environment variable or by using <a class="reference internal" href="../using/cmdline.html#cmdoption-X"><code class="xref std std-option docutils literal notranslate"><span class="pre">-X</span></code></a>

  1057. <code class="docutils literal notranslate"><span class="pre">faulthandler</span></code> command line option.</p>

  1058. <p>Example of a segmentation fault on Linux:</p>

  1059. <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>python<span class="w"> </span>-q<span class="w"> </span>-X<span class="w"> </span>faulthandler

  1060. <span class="go">&gt;&gt;&gt; import ctypes</span>

  1061. <span class="go">&gt;&gt;&gt; ctypes.string_at(0)</span>

  1062. <span class="go">Fatal Python error: Segmentation fault</span>

  1063. 

  1064. <span class="go">Current thread 0x00007fb899f39700:</span>

  1065. <span class="go">  File &quot;/home/python/cpython/Lib/ctypes/__init__.py&quot;, line 486 in string_at</span>

  1066. <span class="go">  File &quot;&lt;stdin&gt;&quot;, line 1 in &lt;module&gt;</span>

  1067. <span class="go">Segmentation fault</span>

  1068. </pre></div>

  1069. </div>

  1070. </section>

  1071. <section id="ipaddress">

  1072. <h3>ipaddress<a class="headerlink" href="#ipaddress" title="Link to this heading">¶</a></h3>

  1073. <p>The new <a class="reference internal" href="../library/ipaddress.html#module-ipaddress" title="ipaddress: IPv4/IPv6 manipulation library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">ipaddress</span></code></a> module provides tools for creating and manipulating

  1074. objects representing IPv4 and IPv6 addresses, networks and interfaces (i.e.

  1075. an IP address associated with a specific IP subnet).</p>

  1076. <p>(Contributed by Google and Peter Moody in <span class="target" id="index-25"></span><a class="pep reference external" href="https://peps.python.org/pep-3144/"><strong>PEP 3144</strong></a>.)</p>

  1077. </section>

  1078. <section id="lzma">

  1079. <h3>lzma<a class="headerlink" href="#lzma" title="Link to this heading">¶</a></h3>

  1080. <p>The newly added <a class="reference internal" href="../library/lzma.html#module-lzma" title="lzma: A Python wrapper for the liblzma compression library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">lzma</span></code></a> module provides data compression and decompression

  1081. using the LZMA algorithm, including support for the <code class="docutils literal notranslate"><span class="pre">.xz</span></code> and <code class="docutils literal notranslate"><span class="pre">.lzma</span></code>

  1082. file formats.</p>

  1083. <p>(Contributed by Nadeem Vawda and Per Øyvind Karlsen in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6715">bpo-6715</a>.)</p>

  1084. </section>

  1085. </section>

  1086. <section id="improved-modules">

  1087. <h2>Improved Modules<a class="headerlink" href="#improved-modules" title="Link to this heading">¶</a></h2>

  1088. <section id="abc">

  1089. <h3>abc<a class="headerlink" href="#abc" title="Link to this heading">¶</a></h3>

  1090. <p>Improved support for abstract base classes containing descriptors composed with

  1091. abstract methods. The recommended approach to declaring abstract descriptors is

  1092. now to provide <code class="xref py py-attr docutils literal notranslate"><span class="pre">__isabstractmethod__</span></code> as a dynamically updated

  1093. property. The built-in descriptors have been updated accordingly.</p>

  1094. <ul class="simple">

  1095. <li><p><a class="reference internal" href="../library/abc.html#abc.abstractproperty" title="abc.abstractproperty"><code class="xref py py-class docutils literal notranslate"><span class="pre">abc.abstractproperty</span></code></a> has been deprecated, use <a class="reference internal" href="../library/functions.html#property" title="property"><code class="xref py py-class docutils literal notranslate"><span class="pre">property</span></code></a>

  1096. with <a class="reference internal" href="../library/abc.html#abc.abstractmethod" title="abc.abstractmethod"><code class="xref py py-func docutils literal notranslate"><span class="pre">abc.abstractmethod()</span></code></a> instead.</p></li>

  1097. <li><p><a class="reference internal" href="../library/abc.html#abc.abstractclassmethod" title="abc.abstractclassmethod"><code class="xref py py-class docutils literal notranslate"><span class="pre">abc.abstractclassmethod</span></code></a> has been deprecated, use

  1098. <a class="reference internal" href="../library/functions.html#classmethod" title="classmethod"><code class="xref py py-class docutils literal notranslate"><span class="pre">classmethod</span></code></a> with <a class="reference internal" href="../library/abc.html#abc.abstractmethod" title="abc.abstractmethod"><code class="xref py py-func docutils literal notranslate"><span class="pre">abc.abstractmethod()</span></code></a> instead.</p></li>

  1099. <li><p><a class="reference internal" href="../library/abc.html#abc.abstractstaticmethod" title="abc.abstractstaticmethod"><code class="xref py py-class docutils literal notranslate"><span class="pre">abc.abstractstaticmethod</span></code></a> has been deprecated, use

  1100. <a class="reference internal" href="../library/functions.html#staticmethod" title="staticmethod"><code class="xref py py-class docutils literal notranslate"><span class="pre">staticmethod</span></code></a> with <a class="reference internal" href="../library/abc.html#abc.abstractmethod" title="abc.abstractmethod"><code class="xref py py-func docutils literal notranslate"><span class="pre">abc.abstractmethod()</span></code></a> instead.</p></li>

  1101. </ul>

  1102. <p>(Contributed by Darren Dale in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11610">bpo-11610</a>.)</p>

  1103. <p><a class="reference internal" href="../library/abc.html#abc.ABCMeta.register" title="abc.ABCMeta.register"><code class="xref py py-meth docutils literal notranslate"><span class="pre">abc.ABCMeta.register()</span></code></a> now returns the registered subclass, which means

  1104. it can now be used as a class decorator (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10868">bpo-10868</a>).</p>

  1105. </section>

  1106. <section id="array">

  1107. <h3>array<a class="headerlink" href="#array" title="Link to this heading">¶</a></h3>

  1108. <p>The <a class="reference internal" href="../library/array.html#module-array" title="array: Space efficient arrays of uniformly typed numeric values."><code class="xref py py-mod docutils literal notranslate"><span class="pre">array</span></code></a> module supports the <span class="c-expr sig sig-inline c"><span class="kt">long</span><span class="w"> </span><span class="kt">long</span></span> type using <code class="docutils literal notranslate"><span class="pre">q</span></code> and

  1109. <code class="docutils literal notranslate"><span class="pre">Q</span></code> type codes.</p>

  1110. <p>(Contributed by Oren Tirosh and Hirokazu Yamamoto in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1172711">bpo-1172711</a>.)</p>

  1111. </section>

  1112. <section id="base64">

  1113. <h3>base64<a class="headerlink" href="#base64" title="Link to this heading">¶</a></h3>

  1114. <p>ASCII-only Unicode strings are now accepted by the decoding functions of the

  1115. <a class="reference internal" href="../library/base64.html#module-base64" title="base64: RFC 4648: Base16, Base32, Base64 Data Encodings; Base85 and Ascii85"><code class="xref py py-mod docutils literal notranslate"><span class="pre">base64</span></code></a> modern interface. For example, <code class="docutils literal notranslate"><span class="pre">base64.b64decode('YWJj')</span></code>

  1116. returns <code class="docutils literal notranslate"><span class="pre">b'abc'</span></code>.  (Contributed by Catalin Iacob in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13641">bpo-13641</a>.)</p>

  1117. </section>

  1118. <section id="binascii">

  1119. <h3>binascii<a class="headerlink" href="#binascii" title="Link to this heading">¶</a></h3>

  1120. <p>In addition to the binary objects they normally accept, the <code class="docutils literal notranslate"><span class="pre">a2b_</span></code> functions

  1121. now all also accept ASCII-only strings as input.  (Contributed by Antoine

  1122. Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13637">bpo-13637</a>.)</p>

  1123. </section>

  1124. <section id="bz2">

  1125. <h3>bz2<a class="headerlink" href="#bz2" title="Link to this heading">¶</a></h3>

  1126. <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 has been rewritten from scratch. In the process, several

  1127. new features have been added:</p>

  1128. <ul>

  1129. <li><p>New <a class="reference internal" href="../library/bz2.html#bz2.open" title="bz2.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">bz2.open()</span></code></a> function: open a bzip2-compressed file in binary or

  1130. text mode.</p></li>

  1131. <li><p><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">bz2.BZ2File</span></code></a> can now read from and write to arbitrary file-like

  1132. objects, by means of its constructor’s <em>fileobj</em> argument.</p>

  1133. <p>(Contributed by Nadeem Vawda in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5863">bpo-5863</a>.)</p>

  1134. </li>

  1135. <li><p><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">bz2.BZ2File</span></code></a> and <a class="reference internal" href="../library/bz2.html#bz2.decompress" title="bz2.decompress"><code class="xref py py-func docutils literal notranslate"><span class="pre">bz2.decompress()</span></code></a> can now decompress

  1136. multi-stream inputs (such as those produced by the <strong class="program">pbzip2</strong> tool).

  1137. <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">bz2.BZ2File</span></code></a> can now also be used to create this type of file, using

  1138. the <code class="docutils literal notranslate"><span class="pre">'a'</span></code> (append) mode.</p>

  1139. <p>(Contributed by Nir Aides in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1625">bpo-1625</a>.)</p>

  1140. </li>

  1141. <li><p><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">bz2.BZ2File</span></code></a> now implements all of 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> API,

  1142. except for the <code class="xref py py-meth docutils literal notranslate"><span class="pre">detach()</span></code> and <code class="xref py py-meth docutils literal notranslate"><span class="pre">truncate()</span></code> methods.</p></li>

  1143. </ul>

  1144. </section>

  1145. <section id="codecs">

  1146. <h3>codecs<a class="headerlink" href="#codecs" title="Link to this heading">¶</a></h3>

  1147. <p>The <a class="reference internal" href="../library/codecs.html#module-encodings.mbcs" title="encodings.mbcs: Windows ANSI codepage"><code class="xref py py-mod docutils literal notranslate"><span class="pre">mbcs</span></code></a> codec has been rewritten to handle correctly

  1148. <code class="docutils literal notranslate"><span class="pre">replace</span></code> and <code class="docutils literal notranslate"><span class="pre">ignore</span></code> error handlers on all Windows versions.  The

  1149. <a class="reference internal" href="../library/codecs.html#module-encodings.mbcs" title="encodings.mbcs: Windows ANSI codepage"><code class="xref py py-mod docutils literal notranslate"><span class="pre">mbcs</span></code></a> codec now supports all error handlers, instead of only

  1150. <code class="docutils literal notranslate"><span class="pre">replace</span></code> to encode and <code class="docutils literal notranslate"><span class="pre">ignore</span></code> to decode.</p>

  1151. <p>A new Windows-only codec has been added: <code class="docutils literal notranslate"><span class="pre">cp65001</span></code> (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13216">bpo-13216</a>). It is the

  1152. Windows code page 65001 (Windows UTF-8, <code class="docutils literal notranslate"><span class="pre">CP_UTF8</span></code>).  For example, it is used

  1153. by <code class="docutils literal notranslate"><span class="pre">sys.stdout</span></code> if the console output code page is set to cp65001 (e.g., using

  1154. <code class="docutils literal notranslate"><span class="pre">chcp</span> <span class="pre">65001</span></code> command).</p>

  1155. <p>Multibyte CJK decoders now resynchronize faster.  They only ignore the first

  1156. byte of an invalid byte sequence. For example, <code class="docutils literal notranslate"><span class="pre">b'\xff\n'.decode('gb2312',</span>

  1157. <span class="pre">'replace')</span></code> now returns a <code class="docutils literal notranslate"><span class="pre">\n</span></code> after the replacement character.</p>

  1158. <p>(<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12016">bpo-12016</a>)</p>

  1159. <p>Incremental CJK codec encoders are no longer reset at each call to their

  1160. encode() methods. For example:</p>

  1161. <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">codecs</span>

  1162. <span class="gp">&gt;&gt;&gt; </span><span class="n">encoder</span> <span class="o">=</span> <span class="n">codecs</span><span class="o">.</span><span class="n">getincrementalencoder</span><span class="p">(</span><span class="s1">&#39;hz&#39;</span><span class="p">)(</span><span class="s1">&#39;strict&#39;</span><span class="p">)</span>

  1163. <span class="gp">&gt;&gt;&gt; </span><span class="sa">b</span><span class="s1">&#39;&#39;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">encoder</span><span class="o">.</span><span class="n">encode</span><span class="p">(</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="s1">&#39;</span><span class="se">\u52ff\u65bd\u65bc\u4eba\u3002</span><span class="s1"> Bye.&#39;</span><span class="p">)</span>

  1164. <span class="go">b&#39;~{NpJ)l6HK!#~} Bye.&#39;</span>

  1165. </pre></div>

  1166. </div>

  1167. <p>This example gives <code class="docutils literal notranslate"><span class="pre">b'~{Np~}~{J)~}~{l6~}~{HK~}~{!#~}</span> <span class="pre">Bye.'</span></code> with older Python

  1168. versions.</p>

  1169. <p>(<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12100">bpo-12100</a>)</p>

  1170. <p>The <code class="docutils literal notranslate"><span class="pre">unicode_internal</span></code> codec has been deprecated.</p>

  1171. </section>

  1172. <section id="collections">

  1173. <h3>collections<a class="headerlink" href="#collections" title="Link to this heading">¶</a></h3>

  1174. <p>Addition of a new <a class="reference internal" href="../library/collections.html#collections.ChainMap" title="collections.ChainMap"><code class="xref py py-class docutils literal notranslate"><span class="pre">ChainMap</span></code></a> class to allow treating a

  1175. number of mappings as a single unit.  (Written by Raymond Hettinger for

  1176. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11089">bpo-11089</a>, made public in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11297">bpo-11297</a>.)</p>

  1177. <p>The abstract base classes have been moved in a new <a class="reference internal" href="../library/collections.abc.html#module-collections.abc" title="collections.abc: Abstract base classes for containers"><code class="xref py py-mod docutils literal notranslate"><span class="pre">collections.abc</span></code></a>

  1178. module, to better differentiate between the abstract and the concrete

  1179. collections classes.  Aliases for ABCs are still present in the

  1180. <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 to preserve existing imports.  (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11085">bpo-11085</a>)</p>

  1181. <p>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 now supports the unary <code class="docutils literal notranslate"><span class="pre">+</span></code> and <code class="docutils literal notranslate"><span class="pre">-</span></code>

  1182. operators, as well as the in-place operators <code class="docutils literal notranslate"><span class="pre">+=</span></code>, <code class="docutils literal notranslate"><span class="pre">-=</span></code>, <code class="docutils literal notranslate"><span class="pre">|=</span></code>, and

  1183. <code class="docutils literal notranslate"><span class="pre">&amp;=</span></code>.  (Contributed by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13121">bpo-13121</a>.)</p>

  1184. </section>

  1185. <section id="contextlib">

  1186. <h3>contextlib<a class="headerlink" href="#contextlib" title="Link to this heading">¶</a></h3>

  1187. <p><a class="reference internal" href="../library/contextlib.html#contextlib.ExitStack" title="contextlib.ExitStack"><code class="xref py py-class docutils literal notranslate"><span class="pre">ExitStack</span></code></a> now provides a solid foundation for

  1188. programmatic manipulation of context managers and similar cleanup

  1189. functionality. Unlike the previous <code class="docutils literal notranslate"><span class="pre">contextlib.nested</span></code> API (which was

  1190. deprecated and removed), the new API is designed to work correctly

  1191. regardless of whether context managers acquire their resources in

  1192. their <code class="docutils literal notranslate"><span class="pre">__init__</span></code> method (for example, file objects) or in their

  1193. <code class="docutils literal notranslate"><span class="pre">__enter__</span></code> method (for example, synchronisation objects from the

  1194. <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).</p>

  1195. <p>(<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13585">bpo-13585</a>)</p>

  1196. </section>

  1197. <section id="crypt">

  1198. <h3>crypt<a class="headerlink" href="#crypt" title="Link to this heading">¶</a></h3>

  1199. <p>Addition of salt and modular crypt format (hashing method) and the <a class="reference internal" href="../library/crypt.html#crypt.mksalt" title="crypt.mksalt"><code class="xref py py-func docutils literal notranslate"><span class="pre">mksalt()</span></code></a>

  1200. function to the <a class="reference internal" href="../library/crypt.html#module-crypt" title="crypt: The crypt() function used to check Unix passwords. (deprecated) (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">crypt</span></code></a> module.</p>

  1201. <p>(<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10924">bpo-10924</a>)</p>

  1202. </section>

  1203. <section id="curses">

  1204. <h3>curses<a class="headerlink" href="#curses" title="Link to this heading">¶</a></h3>

  1205. <ul class="simple">

  1206. <li><p>If the <a class="reference internal" href="../library/curses.html#module-curses" title="curses: An interface to the curses library, providing portable terminal handling. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">curses</span></code></a> module is linked to the ncursesw library, use Unicode

  1207. functions when Unicode strings or characters are passed (e.g.

  1208. <code class="xref c c-func docutils literal notranslate"><span class="pre">waddwstr()</span></code>), and bytes functions otherwise (e.g. <code class="xref c c-func docutils literal notranslate"><span class="pre">waddstr()</span></code>).</p></li>

  1209. <li><p>Use the locale encoding instead of <code class="docutils literal notranslate"><span class="pre">utf-8</span></code> to encode Unicode strings.</p></li>

  1210. <li><p><code class="xref py py-class docutils literal notranslate"><span class="pre">curses.window</span></code> has a new <a class="reference internal" href="../library/curses.html#curses.window.encoding" title="curses.window.encoding"><code class="xref py py-attr docutils literal notranslate"><span class="pre">curses.window.encoding</span></code></a> attribute.</p></li>

  1211. <li><p>The <code class="xref py py-class docutils literal notranslate"><span class="pre">curses.window</span></code> class has a new <a class="reference internal" href="../library/curses.html#curses.window.get_wch" title="curses.window.get_wch"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_wch()</span></code></a>

  1212. method to get a wide character</p></li>

  1213. <li><p>The <a class="reference internal" href="../library/curses.html#module-curses" title="curses: An interface to the curses library, providing portable terminal handling. (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">curses</span></code></a> module has a new <a class="reference internal" href="../library/curses.html#curses.unget_wch" title="curses.unget_wch"><code class="xref py py-meth docutils literal notranslate"><span class="pre">unget_wch()</span></code></a> function to

  1214. push a wide character so the next <a class="reference internal" href="../library/curses.html#curses.window.get_wch" title="curses.window.get_wch"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_wch()</span></code></a> will return

  1215. it</p></li>

  1216. </ul>

  1217. <p>(Contributed by Iñigo Serna in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6755">bpo-6755</a>.)</p>

  1218. </section>

  1219. <section id="datetime">

  1220. <h3>datetime<a class="headerlink" href="#datetime" title="Link to this heading">¶</a></h3>

  1221. <ul class="simple">

  1222. <li><p>Equality comparisons between naive and aware <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>

  1223. instances now return <a class="reference internal" href="../library/constants.html#False" title="False"><code class="xref py py-const docutils literal notranslate"><span class="pre">False</span></code></a> instead of raising <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>

  1224. (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=15006">bpo-15006</a>).</p></li>

  1225. <li><p>New <a class="reference internal" href="../library/datetime.html#datetime.datetime.timestamp" title="datetime.datetime.timestamp"><code class="xref py py-meth docutils literal notranslate"><span class="pre">datetime.datetime.timestamp()</span></code></a> method: Return POSIX timestamp

  1226. corresponding to the <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> instance.</p></li>

  1227. <li><p>The <a class="reference internal" href="../library/datetime.html#datetime.datetime.strftime" title="datetime.datetime.strftime"><code class="xref py py-meth docutils literal notranslate"><span class="pre">datetime.datetime.strftime()</span></code></a> method supports formatting years

  1228. older than 1000.</p></li>

  1229. <li><p>The <a class="reference internal" href="../library/datetime.html#datetime.datetime.astimezone" title="datetime.datetime.astimezone"><code class="xref py py-meth docutils literal notranslate"><span class="pre">datetime.datetime.astimezone()</span></code></a> method can now be

  1230. called without arguments to convert datetime instance to the system

  1231. timezone.</p></li>

  1232. </ul>

  1233. </section>

  1234. <section id="decimal">

  1235. <span id="new-decimal"></span><h3>decimal<a class="headerlink" href="#decimal" title="Link to this heading">¶</a></h3>

  1236. <dl class="simple">

  1237. <dt><a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7652">bpo-7652</a> - integrate fast native decimal arithmetic.</dt><dd><p>C-module and libmpdec written by Stefan Krah.</p>

  1238. </dd>

  1239. </dl>

  1240. <p>The new C version of the decimal module integrates the high speed libmpdec

  1241. library for arbitrary precision correctly rounded decimal floating point

  1242. arithmetic. libmpdec conforms to IBM’s General Decimal Arithmetic Specification.</p>

  1243. <p>Performance gains range from 10x for database applications to 100x for

  1244. numerically intensive applications. These numbers are expected gains

  1245. for standard precisions used in decimal floating point arithmetic. Since

  1246. the precision is user configurable, the exact figures may vary. For example,

  1247. in integer bignum arithmetic the differences can be significantly higher.</p>

  1248. <p>The following table is meant as an illustration. Benchmarks are available

  1249. at <a class="reference external" href="https://www.bytereef.org/mpdecimal/quickstart.html">https://www.bytereef.org/mpdecimal/quickstart.html</a>.</p>

  1250. <blockquote>

  1251. <div><table class="docutils align-default">

  1252. <thead>

  1253. <tr class="row-odd"><th class="head"></th>

  1254. <th class="head"><p>decimal.py</p></th>

  1255. <th class="head"><p>_decimal</p></th>

  1256. <th class="head"><p>speedup</p></th>

  1257. </tr>

  1258. </thead>

  1259. <tbody>

  1260. <tr class="row-even"><td><p>pi</p></td>

  1261. <td><p>42.02s</p></td>

  1262. <td><p>0.345s</p></td>

  1263. <td><p>120x</p></td>

  1264. </tr>

  1265. <tr class="row-odd"><td><p>telco</p></td>

  1266. <td><p>172.19s</p></td>

  1267. <td><p>5.68s</p></td>

  1268. <td><p>30x</p></td>

  1269. </tr>

  1270. <tr class="row-even"><td><p>psycopg</p></td>

  1271. <td><p>3.57s</p></td>

  1272. <td><p>0.29s</p></td>

  1273. <td><p>12x</p></td>

  1274. </tr>

  1275. </tbody>

  1276. </table>

  1277. </div></blockquote>

  1278. <section id="id1">

  1279. <h4>Features<a class="headerlink" href="#id1" title="Link to this heading">¶</a></h4>

  1280. <ul class="simple">

  1281. <li><p>The <a class="reference internal" href="../library/decimal.html#decimal.FloatOperation" title="decimal.FloatOperation"><code class="xref py py-exc docutils literal notranslate"><span class="pre">FloatOperation</span></code></a> signal optionally enables stricter

  1282. semantics for mixing floats and Decimals.</p></li>

  1283. <li><p>If Python is compiled without threads, the C version automatically

  1284. disables the expensive thread local context machinery. In this case,

  1285. the variable <a class="reference internal" href="../library/decimal.html#decimal.HAVE_THREADS" title="decimal.HAVE_THREADS"><code class="xref py py-const docutils literal notranslate"><span class="pre">HAVE_THREADS</span></code></a> is set to <code class="docutils literal notranslate"><span class="pre">False</span></code>.</p></li>

  1286. </ul>

  1287. </section>

  1288. <section id="id2">

  1289. <h4>API changes<a class="headerlink" href="#id2" title="Link to this heading">¶</a></h4>

  1290. <ul>

  1291. <li><p>The C module has the following context limits, depending on the machine

  1292. architecture:</p>

  1293. <blockquote>

  1294. <div><table class="docutils align-default">

  1295. <thead>

  1296. <tr class="row-odd"><th class="head"></th>

  1297. <th class="head"><p>32-bit</p></th>

  1298. <th class="head"><p>64-bit</p></th>

  1299. </tr>

  1300. </thead>

  1301. <tbody>

  1302. <tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">MAX_PREC</span></code></p></td>

  1303. <td><p><code class="docutils literal notranslate"><span class="pre">425000000</span></code></p></td>

  1304. <td><p><code class="docutils literal notranslate"><span class="pre">999999999999999999</span></code></p></td>

  1305. </tr>

  1306. <tr class="row-odd"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">MAX_EMAX</span></code></p></td>

  1307. <td><p><code class="docutils literal notranslate"><span class="pre">425000000</span></code></p></td>

  1308. <td><p><code class="docutils literal notranslate"><span class="pre">999999999999999999</span></code></p></td>

  1309. </tr>

  1310. <tr class="row-even"><td><p><code class="xref py py-const docutils literal notranslate"><span class="pre">MIN_EMIN</span></code></p></td>

  1311. <td><p><code class="docutils literal notranslate"><span class="pre">-425000000</span></code></p></td>

  1312. <td><p><code class="docutils literal notranslate"><span class="pre">-999999999999999999</span></code></p></td>

  1313. </tr>

  1314. </tbody>

  1315. </table>

  1316. </div></blockquote>

  1317. </li>

  1318. <li><p>In the context templates (<a class="reference internal" href="../library/decimal.html#decimal.DefaultContext" title="decimal.DefaultContext"><code class="xref py py-class docutils literal notranslate"><span class="pre">DefaultContext</span></code></a>,

  1319. <a class="reference internal" href="../library/decimal.html#decimal.BasicContext" title="decimal.BasicContext"><code class="xref py py-class docutils literal notranslate"><span class="pre">BasicContext</span></code></a> and <a class="reference internal" href="../library/decimal.html#decimal.ExtendedContext" title="decimal.ExtendedContext"><code class="xref py py-class docutils literal notranslate"><span class="pre">ExtendedContext</span></code></a>)

  1320. the magnitude of <code class="xref py py-attr docutils literal notranslate"><span class="pre">Emax</span></code> and

  1321. <code class="xref py py-attr docutils literal notranslate"><span class="pre">Emin</span></code> has changed to <code class="docutils literal notranslate"><span class="pre">999999</span></code>.</p></li>

  1322. <li><p>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> constructor in decimal.py does not observe

  1323. the context limits and converts values with arbitrary exponents or precision

  1324. exactly. Since the C version has internal limits, the following scheme is

  1325. used: If possible, values are converted exactly, otherwise

  1326. <a class="reference internal" href="../library/decimal.html#decimal.InvalidOperation" title="decimal.InvalidOperation"><code class="xref py py-exc docutils literal notranslate"><span class="pre">InvalidOperation</span></code></a> is raised and the result is NaN. In the

  1327. latter case it is always possible to use <a class="reference internal" href="../library/decimal.html#decimal.Context.create_decimal" title="decimal.Context.create_decimal"><code class="xref py py-meth docutils literal notranslate"><span class="pre">create_decimal()</span></code></a>

  1328. in order to obtain a rounded or inexact value.</p></li>

  1329. <li><p>The power function in decimal.py is always correctly rounded. In the

  1330. C version, it is defined in terms of the correctly rounded

  1331. <a class="reference internal" href="../library/decimal.html#decimal.Decimal.exp" title="decimal.Decimal.exp"><code class="xref py py-meth docutils literal notranslate"><span class="pre">exp()</span></code></a> and <a class="reference internal" href="../library/decimal.html#decimal.Decimal.ln" title="decimal.Decimal.ln"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ln()</span></code></a> functions,

  1332. but the final result is only “almost always correctly rounded”.</p></li>

  1333. <li><p>In the C version, the context dictionary containing the signals is a

  1334. <a class="reference internal" href="../library/collections.abc.html#collections.abc.MutableMapping" title="collections.abc.MutableMapping"><code class="xref py py-class docutils literal notranslate"><span class="pre">MutableMapping</span></code></a>.  For speed reasons,

  1335. <code class="xref py py-attr docutils literal notranslate"><span class="pre">flags</span></code> and <code class="xref py py-attr docutils literal notranslate"><span class="pre">traps</span></code> always

  1336. refer to the same <a class="reference internal" href="../library/collections.abc.html#collections.abc.MutableMapping" title="collections.abc.MutableMapping"><code class="xref py py-class docutils literal notranslate"><span class="pre">MutableMapping</span></code></a> that the context

  1337. was initialized with. If a new signal dictionary is assigned,

  1338. <code class="xref py py-attr docutils literal notranslate"><span class="pre">flags</span></code> and <code class="xref py py-attr docutils literal notranslate"><span class="pre">traps</span></code>

  1339. are updated with the new values, but they do not reference the RHS

  1340. dictionary.</p></li>

  1341. <li><p>Pickling a <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> produces a different output in order

  1342. to have a common interchange format for the Python and C versions.</p></li>

  1343. <li><p>The order of arguments in 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> constructor has been

  1344. changed to match the order displayed by <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>.</p></li>

  1345. <li><p>The <code class="docutils literal notranslate"><span class="pre">watchexp</span></code> parameter in the <a class="reference internal" href="../library/decimal.html#decimal.Decimal.quantize" title="decimal.Decimal.quantize"><code class="xref py py-meth docutils literal notranslate"><span class="pre">quantize()</span></code></a> method

  1346. is deprecated.</p></li>

  1347. </ul>

  1348. </section>

  1349. </section>

  1350. <section id="email">

  1351. <span id="new-email"></span><h3>email<a class="headerlink" href="#email" title="Link to this heading">¶</a></h3>

  1352. <section id="policy-framework">

  1353. <h4>Policy Framework<a class="headerlink" href="#policy-framework" title="Link to this heading">¶</a></h4>

  1354. <p>The email package now has a <a class="reference internal" href="../library/email.policy.html#module-email.policy" title="email.policy: Controlling the parsing and generating of messages"><code class="xref py py-mod docutils literal notranslate"><span class="pre">policy</span></code></a> framework.  A

  1355. <a class="reference internal" href="../library/email.policy.html#email.policy.Policy" title="email.policy.Policy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Policy</span></code></a> is an object with several methods and properties

  1356. that control how the email package behaves.  The primary policy for Python 3.3

  1357. is the <a class="reference internal" href="../library/email.policy.html#email.policy.Compat32" title="email.policy.Compat32"><code class="xref py py-class docutils literal notranslate"><span class="pre">Compat32</span></code></a> policy, which provides backward

  1358. compatibility with the email package in Python 3.2.  A <code class="docutils literal notranslate"><span class="pre">policy</span></code> can be

  1359. specified when an email message is parsed by a <a class="reference internal" href="../library/email.parser.html#module-email.parser" title="email.parser: Parse flat text email messages to produce a message object structure."><code class="xref py py-mod docutils literal notranslate"><span class="pre">parser</span></code></a>, or when a

  1360. <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> object is created, or when an email is

  1361. serialized using a <a class="reference internal" href="../library/email.generator.html#module-email.generator" title="email.generator: Generate flat text email messages from a message structure."><code class="xref py py-mod docutils literal notranslate"><span class="pre">generator</span></code></a>.  Unless overridden, a policy passed

  1362. to a <code class="docutils literal notranslate"><span class="pre">parser</span></code> is inherited by all the <code class="docutils literal notranslate"><span class="pre">Message</span></code> object and sub-objects

  1363. created by the <code class="docutils literal notranslate"><span class="pre">parser</span></code>.  By default a <code class="docutils literal notranslate"><span class="pre">generator</span></code> will use the policy of

  1364. the <code class="docutils literal notranslate"><span class="pre">Message</span></code> object it is serializing.  The default policy is

  1365. <a class="reference internal" href="../library/email.policy.html#email.policy.compat32" title="email.policy.compat32"><code class="xref py py-data docutils literal notranslate"><span class="pre">compat32</span></code></a>.</p>

  1366. <p>The minimum set of controls implemented by all <code class="docutils literal notranslate"><span class="pre">policy</span></code> objects are:</p>

  1367. <table class="docutils align-default">

  1368. <tbody>

  1369. <tr class="row-odd"><td><p>max_line_length</p></td>

  1370. <td><p>The maximum length, excluding the linesep character(s),

  1371. individual lines may have when a <code class="docutils literal notranslate"><span class="pre">Message</span></code> is

  1372. serialized.  Defaults to 78.</p></td>

  1373. </tr>

  1374. <tr class="row-even"><td><p>linesep</p></td>

  1375. <td><p>The character used to separate individual lines when a

  1376. <code class="docutils literal notranslate"><span class="pre">Message</span></code> is serialized.  Defaults to <code class="docutils literal notranslate"><span class="pre">\n</span></code>.</p></td>

  1377. </tr>

  1378. <tr class="row-odd"><td><p>cte_type</p></td>

  1379. <td><p><code class="docutils literal notranslate"><span class="pre">7bit</span></code> or <code class="docutils literal notranslate"><span class="pre">8bit</span></code>.  <code class="docutils literal notranslate"><span class="pre">8bit</span></code> applies only to a

  1380. <code class="docutils literal notranslate"><span class="pre">Bytes</span></code> <code class="docutils literal notranslate"><span class="pre">generator</span></code>, and means that non-ASCII may

  1381. be used where allowed by the protocol (or where it

  1382. exists in the original input).</p></td>

  1383. </tr>

  1384. <tr class="row-even"><td><p>raise_on_defect</p></td>

  1385. <td><p>Causes a <code class="docutils literal notranslate"><span class="pre">parser</span></code> to raise error when defects are

  1386. encountered instead of adding them to the <code class="docutils literal notranslate"><span class="pre">Message</span></code>

  1387. object’s <code class="docutils literal notranslate"><span class="pre">defects</span></code> list.</p></td>

  1388. </tr>

  1389. </tbody>

  1390. </table>

  1391. <p>A new policy instance, with new settings, is created using the

  1392. <a class="reference internal" href="../library/email.policy.html#email.policy.Policy.clone" title="email.policy.Policy.clone"><code class="xref py py-meth docutils literal notranslate"><span class="pre">clone()</span></code></a> method of policy objects.  <code class="docutils literal notranslate"><span class="pre">clone</span></code> takes

  1393. any of the above controls as keyword arguments.  Any control not specified in

  1394. the call retains its default value.  Thus you can create a policy that uses

  1395. <code class="docutils literal notranslate"><span class="pre">\r\n</span></code> linesep characters like this:</p>

  1396. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">mypolicy</span> <span class="o">=</span> <span class="n">compat32</span><span class="o">.</span><span class="n">clone</span><span class="p">(</span><span class="n">linesep</span><span class="o">=</span><span class="s1">&#39;</span><span class="se">\r\n</span><span class="s1">&#39;</span><span class="p">)</span>

  1397. </pre></div>

  1398. </div>

  1399. <p>Policies can be used to make the generation of messages in the format needed by

  1400. your application simpler.  Instead of having to remember to specify

  1401. <code class="docutils literal notranslate"><span class="pre">linesep='\r\n'</span></code> in all the places you call a <code class="docutils literal notranslate"><span class="pre">generator</span></code>, you can specify

  1402. it once, when you set the policy used by the <code class="docutils literal notranslate"><span class="pre">parser</span></code> or the <code class="docutils literal notranslate"><span class="pre">Message</span></code>,

  1403. whichever your program uses to create <code class="docutils literal notranslate"><span class="pre">Message</span></code> objects.  On the other hand,

  1404. if you need to generate messages in multiple forms, you can still specify the

  1405. parameters in the appropriate <code class="docutils literal notranslate"><span class="pre">generator</span></code> call.  Or you can have custom

  1406. policy instances for your different cases, and pass those in when you create

  1407. the <code class="docutils literal notranslate"><span class="pre">generator</span></code>.</p>

  1408. </section>

  1409. <section id="provisional-policy-with-new-header-api">

  1410. <h4>Provisional Policy with New Header API<a class="headerlink" href="#provisional-policy-with-new-header-api" title="Link to this heading">¶</a></h4>

  1411. <p>While the policy framework is worthwhile all by itself, the main motivation for

  1412. introducing it is to allow the creation of new policies that implement new

  1413. features for the email package in a way that maintains backward compatibility

  1414. for those who do not use the new policies.  Because the new policies introduce a

  1415. new API, we are releasing them in Python 3.3 as a <a class="reference internal" href="../glossary.html#term-provisional-package"><span class="xref std std-term">provisional policy</span></a>.  Backwards incompatible changes (up to and including

  1416. removal of the code) may occur if deemed necessary by the core developers.</p>

  1417. <p>The new policies are instances of <a class="reference internal" href="../library/email.policy.html#email.policy.EmailPolicy" title="email.policy.EmailPolicy"><code class="xref py py-class docutils literal notranslate"><span class="pre">EmailPolicy</span></code></a>,

  1418. and add the following additional controls:</p>

  1419. <table class="docutils align-default">

  1420. <tbody>

  1421. <tr class="row-odd"><td><p>refold_source</p></td>

  1422. <td><p>Controls whether or not headers parsed by a

  1423. <a class="reference internal" href="../library/email.parser.html#module-email.parser" title="email.parser: Parse flat text email messages to produce a message object structure."><code class="xref py py-mod docutils literal notranslate"><span class="pre">parser</span></code></a> are refolded by the

  1424. <a class="reference internal" href="../library/email.generator.html#module-email.generator" title="email.generator: Generate flat text email messages from a message structure."><code class="xref py py-mod docutils literal notranslate"><span class="pre">generator</span></code></a>.  It can be <code class="docutils literal notranslate"><span class="pre">none</span></code>, <code class="docutils literal notranslate"><span class="pre">long</span></code>,

  1425. or <code class="docutils literal notranslate"><span class="pre">all</span></code>.  The default is <code class="docutils literal notranslate"><span class="pre">long</span></code>, which means that

  1426. source headers with a line longer than

  1427. <code class="docutils literal notranslate"><span class="pre">max_line_length</span></code> get refolded.  <code class="docutils literal notranslate"><span class="pre">none</span></code> means no

  1428. line get refolded, and <code class="docutils literal notranslate"><span class="pre">all</span></code> means that all lines

  1429. get refolded.</p></td>

  1430. </tr>

  1431. <tr class="row-even"><td><p>header_factory</p></td>

  1432. <td><p>A callable that take a <code class="docutils literal notranslate"><span class="pre">name</span></code> and <code class="docutils literal notranslate"><span class="pre">value</span></code> and

  1433. produces a custom header object.</p></td>

  1434. </tr>

  1435. </tbody>

  1436. </table>

  1437. <p>The <code class="docutils literal notranslate"><span class="pre">header_factory</span></code> is the key to the new features provided by the new

  1438. policies.  When one of the new policies is used, any header retrieved from

  1439. a <code class="docutils literal notranslate"><span class="pre">Message</span></code> object is an object produced by the <code class="docutils literal notranslate"><span class="pre">header_factory</span></code>, and any

  1440. time you set a header on a <code class="docutils literal notranslate"><span class="pre">Message</span></code> it becomes an object produced by

  1441. <code class="docutils literal notranslate"><span class="pre">header_factory</span></code>.  All such header objects have a <code class="docutils literal notranslate"><span class="pre">name</span></code> attribute equal

  1442. to the header name.  Address and Date headers have additional attributes

  1443. that give you access to the parsed data of the header.  This means you can now

  1444. do things like this:</p>

  1445. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">m</span> <span class="o">=</span> <span class="n">Message</span><span class="p">(</span><span class="n">policy</span><span class="o">=</span><span class="n">SMTP</span><span class="p">)</span>

  1446. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span><span class="p">[</span><span class="s1">&#39;To&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s1">&#39;Éric &lt;foo@example.com&gt;&#39;</span>

  1447. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span><span class="p">[</span><span class="s1">&#39;to&#39;</span><span class="p">]</span>

  1448. <span class="go">&#39;Éric &lt;foo@example.com&gt;&#39;</span>

  1449. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span><span class="p">[</span><span class="s1">&#39;to&#39;</span><span class="p">]</span><span class="o">.</span><span class="n">addresses</span>

  1450. <span class="go">(Address(display_name=&#39;Éric&#39;, username=&#39;foo&#39;, domain=&#39;example.com&#39;),)</span>

  1451. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span><span class="p">[</span><span class="s1">&#39;to&#39;</span><span class="p">]</span><span class="o">.</span><span class="n">addresses</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">username</span>

  1452. <span class="go">&#39;foo&#39;</span>

  1453. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span><span class="p">[</span><span class="s1">&#39;to&#39;</span><span class="p">]</span><span class="o">.</span><span class="n">addresses</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">display_name</span>

  1454. <span class="go">&#39;Éric&#39;</span>

  1455. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span><span class="p">[</span><span class="s1">&#39;Date&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="n">email</span><span class="o">.</span><span class="n">utils</span><span class="o">.</span><span class="n">localtime</span><span class="p">()</span>

  1456. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span><span class="p">[</span><span class="s1">&#39;Date&#39;</span><span class="p">]</span><span class="o">.</span><span class="n">datetime</span>

  1457. <span class="go">datetime.datetime(2012, 5, 25, 21, 39, 24, 465484, tzinfo=datetime.timezone(datetime.timedelta(-1, 72000), &#39;EDT&#39;))</span>

  1458. <span class="gp">&gt;&gt;&gt; </span><span class="n">m</span><span class="p">[</span><span class="s1">&#39;Date&#39;</span><span class="p">]</span>

  1459. <span class="go">&#39;Fri, 25 May 2012 21:44:27 -0400&#39;</span>

  1460. <span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span><span class="p">(</span><span class="n">m</span><span class="p">)</span>

  1461. <span class="go">To: =?utf-8?q?=C3=89ric?= &lt;foo@example.com&gt;</span>

  1462. <span class="go">Date: Fri, 25 May 2012 21:44:27 -0400</span>

  1463. </pre></div>

  1464. </div>

  1465. <p>You will note that the unicode display name is automatically encoded as

  1466. <code class="docutils literal notranslate"><span class="pre">utf-8</span></code> when the message is serialized, but that when the header is accessed

  1467. directly, you get the unicode version.  This eliminates any need to deal with

  1468. the <a class="reference internal" href="../library/email.header.html#module-email.header" title="email.header: Representing non-ASCII headers"><code class="xref py py-mod docutils literal notranslate"><span class="pre">email.header</span></code></a> <a class="reference internal" href="../library/email.header.html#email.header.decode_header" title="email.header.decode_header"><code class="xref py py-meth docutils literal notranslate"><span class="pre">decode_header()</span></code></a> or

  1469. <a class="reference internal" href="../library/email.header.html#email.header.make_header" title="email.header.make_header"><code class="xref py py-meth docutils literal notranslate"><span class="pre">make_header()</span></code></a> functions.</p>

  1470. <p>You can also create addresses from parts:</p>

  1471. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">m</span><span class="p">[</span><span class="s1">&#39;cc&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="p">[</span><span class="n">Group</span><span class="p">(</span><span class="s1">&#39;pals&#39;</span><span class="p">,</span> <span class="p">[</span><span class="n">Address</span><span class="p">(</span><span class="s1">&#39;Bob&#39;</span><span class="p">,</span> <span class="s1">&#39;bob&#39;</span><span class="p">,</span> <span class="s1">&#39;example.com&#39;</span><span class="p">),</span>

  1472. <span class="gp">... </span>                          <span class="n">Address</span><span class="p">(</span><span class="s1">&#39;Sally&#39;</span><span class="p">,</span> <span class="s1">&#39;sally&#39;</span><span class="p">,</span> <span class="s1">&#39;example.com&#39;</span><span class="p">)]),</span>

  1473. <span class="gp">... </span>           <span class="n">Address</span><span class="p">(</span><span class="s1">&#39;Bonzo&#39;</span><span class="p">,</span> <span class="n">addr_spec</span><span class="o">=</span><span class="s1">&#39;bonz@laugh.com&#39;</span><span class="p">)]</span>

  1474. <span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span><span class="p">(</span><span class="n">m</span><span class="p">)</span>

  1475. <span class="go">To: =?utf-8?q?=C3=89ric?= &lt;foo@example.com&gt;</span>

  1476. <span class="go">Date: Fri, 25 May 2012 21:44:27 -0400</span>

  1477. <span class="go">cc: pals: Bob &lt;bob@example.com&gt;, Sally &lt;sally@example.com&gt;;, Bonzo &lt;bonz@laugh.com&gt;</span>

  1478. </pre></div>

  1479. </div>

  1480. <p>Decoding to unicode is done automatically:</p>

  1481. <div class="highlight-python3 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">message_from_string</span><span class="p">(</span><span class="nb">str</span><span class="p">(</span><span class="n">m</span><span class="p">))</span>

  1482. <span class="gp">&gt;&gt;&gt; </span><span class="n">m2</span><span class="p">[</span><span class="s1">&#39;to&#39;</span><span class="p">]</span>

  1483. <span class="go">&#39;Éric &lt;foo@example.com&gt;&#39;</span>

  1484. </pre></div>

  1485. </div>

  1486. <p>When you parse a message, you can use the <code class="docutils literal notranslate"><span class="pre">addresses</span></code> and <code class="docutils literal notranslate"><span class="pre">groups</span></code>

  1487. attributes of the header objects to access the groups and individual

  1488. addresses:</p>

  1489. <div class="highlight-python3 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="s1">&#39;cc&#39;</span><span class="p">]</span><span class="o">.</span><span class="n">addresses</span>

  1490. <span class="go">(Address(display_name=&#39;Bob&#39;, username=&#39;bob&#39;, domain=&#39;example.com&#39;), Address(display_name=&#39;Sally&#39;, username=&#39;sally&#39;, domain=&#39;example.com&#39;), Address(display_name=&#39;Bonzo&#39;, username=&#39;bonz&#39;, domain=&#39;laugh.com&#39;))</span>

  1491. <span class="gp">&gt;&gt;&gt; </span><span class="n">m2</span><span class="p">[</span><span class="s1">&#39;cc&#39;</span><span class="p">]</span><span class="o">.</span><span class="n">groups</span>

  1492. <span class="go">(Group(display_name=&#39;pals&#39;, addresses=(Address(display_name=&#39;Bob&#39;, username=&#39;bob&#39;, domain=&#39;example.com&#39;), Address(display_name=&#39;Sally&#39;, username=&#39;sally&#39;, domain=&#39;example.com&#39;)), Group(display_name=None, addresses=(Address(display_name=&#39;Bonzo&#39;, username=&#39;bonz&#39;, domain=&#39;laugh.com&#39;),))</span>

  1493. </pre></div>

  1494. </div>

  1495. <p>In summary, if you use one of the new policies, header manipulation works the

  1496. way it ought to:  your application works with unicode strings, and the email

  1497. package transparently encodes and decodes the unicode to and from the RFC

  1498. standard Content Transfer Encodings.</p>

  1499. </section>

  1500. <section id="other-api-changes">

  1501. <h4>Other API Changes<a class="headerlink" href="#other-api-changes" title="Link to this heading">¶</a></h4>

  1502. <p>New <a class="reference internal" href="../library/email.parser.html#email.parser.BytesHeaderParser" title="email.parser.BytesHeaderParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">BytesHeaderParser</span></code></a>, added to the <a class="reference internal" href="../library/email.parser.html#module-email.parser" title="email.parser: Parse flat text email messages to produce a message object structure."><code class="xref py py-mod docutils literal notranslate"><span class="pre">parser</span></code></a>

  1503. module to complement <a class="reference internal" href="../library/email.parser.html#email.parser.HeaderParser" title="email.parser.HeaderParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">HeaderParser</span></code></a> and complete the Bytes

  1504. API.</p>

  1505. <p>New utility functions:</p>

  1506. <ul class="simple">

  1507. <li><p><a class="reference internal" href="../library/email.utils.html#email.utils.format_datetime" title="email.utils.format_datetime"><code class="xref py py-func docutils literal notranslate"><span class="pre">format_datetime()</span></code></a>: given a <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>,

  1508. produce a string formatted for use in an email header.</p></li>

  1509. <li><p><a class="reference internal" href="../library/email.utils.html#email.utils.parsedate_to_datetime" title="email.utils.parsedate_to_datetime"><code class="xref py py-func docutils literal notranslate"><span class="pre">parsedate_to_datetime()</span></code></a>: given a date string from

  1510. an email header, convert it into an aware <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>,

  1511. or a naive <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> if the offset is <code class="docutils literal notranslate"><span class="pre">-0000</span></code>.</p></li>

  1512. <li><p><a class="reference internal" href="../library/email.utils.html#email.utils.localtime" title="email.utils.localtime"><code class="xref py py-func docutils literal notranslate"><span class="pre">localtime()</span></code></a>: With no argument, returns the

  1513. current local time as an aware <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> using the local

  1514. <a class="reference internal" href="../library/datetime.html#datetime.timezone" title="datetime.timezone"><code class="xref py py-class docutils literal notranslate"><span class="pre">timezone</span></code></a>.  Given an aware <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>,

  1515. converts it into an aware <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> using the

  1516. local <a class="reference internal" href="../library/datetime.html#datetime.timezone" title="datetime.timezone"><code class="xref py py-class docutils literal notranslate"><span class="pre">timezone</span></code></a>.</p></li>

  1517. </ul>

  1518. </section>

  1519. </section>

  1520. <section id="ftplib">

  1521. <h3>ftplib<a class="headerlink" href="#ftplib" title="Link to this heading">¶</a></h3>

  1522. <ul class="simple">

  1523. <li><p><a class="reference internal" href="../library/ftplib.html#ftplib.FTP" title="ftplib.FTP"><code class="xref py py-class docutils literal notranslate"><span class="pre">ftplib.FTP</span></code></a> now accepts a <code class="docutils literal notranslate"><span class="pre">source_address</span></code> keyword argument to

  1524. specify the <code class="docutils literal notranslate"><span class="pre">(host,</span> <span class="pre">port)</span></code> to use as the source address in the bind call

  1525. when creating the outgoing socket.  (Contributed by Giampaolo Rodolà

  1526. in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8594">bpo-8594</a>.)</p></li>

  1527. <li><p>The <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> class now provides a new

  1528. <a class="reference internal" href="../library/ftplib.html#ftplib.FTP_TLS.ccc" title="ftplib.FTP_TLS.ccc"><code class="xref py py-func docutils literal notranslate"><span class="pre">ccc()</span></code></a> function to revert control channel back to

  1529. plaintext.  This can be useful to take advantage of firewalls that know how

  1530. to handle NAT with non-secure FTP without opening fixed ports.  (Contributed

  1531. by Giampaolo Rodolà in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12139">bpo-12139</a>.)</p></li>

  1532. <li><p>Added <a class="reference internal" href="../library/ftplib.html#ftplib.FTP.mlsd" title="ftplib.FTP.mlsd"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ftplib.FTP.mlsd()</span></code></a> method which provides a parsable directory

  1533. listing format and deprecates <a class="reference internal" href="../library/ftplib.html#ftplib.FTP.nlst" title="ftplib.FTP.nlst"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ftplib.FTP.nlst()</span></code></a> and

  1534. <a class="reference internal" href="../library/ftplib.html#ftplib.FTP.dir" title="ftplib.FTP.dir"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ftplib.FTP.dir()</span></code></a>.  (Contributed by Giampaolo Rodolà in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11072">bpo-11072</a>.)</p></li>

  1535. </ul>

  1536. </section>

  1537. <section id="functools">

  1538. <h3>functools<a class="headerlink" href="#functools" title="Link to this heading">¶</a></h3>

  1539. <p>The <a class="reference internal" href="../library/functools.html#functools.lru_cache" title="functools.lru_cache"><code class="xref py py-func docutils literal notranslate"><span class="pre">functools.lru_cache()</span></code></a> decorator now accepts a <code class="docutils literal notranslate"><span class="pre">typed</span></code> keyword

  1540. argument (that defaults to <code class="docutils literal notranslate"><span class="pre">False</span></code> to ensure that it caches values of

  1541. different types that compare equal in separate cache slots.  (Contributed

  1542. by Raymond Hettinger in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13227">bpo-13227</a>.)</p>

  1543. </section>

  1544. <section id="gc">

  1545. <h3>gc<a class="headerlink" href="#gc" title="Link to this heading">¶</a></h3>

  1546. <p>It is now possible to register callbacks invoked by the garbage collector

  1547. before and after collection using the new <a class="reference internal" href="../library/gc.html#gc.callbacks" title="gc.callbacks"><code class="xref py py-data docutils literal notranslate"><span class="pre">callbacks</span></code></a> list.</p>

  1548. </section>

  1549. <section id="hmac">

  1550. <h3>hmac<a class="headerlink" href="#hmac" title="Link to this heading">¶</a></h3>

  1551. <p>A new <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">compare_digest()</span></code></a> function has been added to prevent side

  1552. channel attacks on digests through timing analysis.  (Contributed by Nick

  1553. Coghlan and Christian Heimes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=15061">bpo-15061</a>.)</p>

  1554. </section>

  1555. <section id="http">

  1556. <h3>http<a class="headerlink" href="#http" title="Link to this heading">¶</a></h3>

  1557. <p><a class="reference internal" href="../library/http.server.html#http.server.BaseHTTPRequestHandler" title="http.server.BaseHTTPRequestHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">http.server.BaseHTTPRequestHandler</span></code></a> now buffers the headers and writes

  1558. them all at once when <a class="reference internal" href="../library/http.server.html#http.server.BaseHTTPRequestHandler.end_headers" title="http.server.BaseHTTPRequestHandler.end_headers"><code class="xref py py-meth docutils literal notranslate"><span class="pre">end_headers()</span></code></a> is

  1559. called.  A new method <a class="reference internal" href="../library/http.server.html#http.server.BaseHTTPRequestHandler.flush_headers" title="http.server.BaseHTTPRequestHandler.flush_headers"><code class="xref py py-meth docutils literal notranslate"><span class="pre">flush_headers()</span></code></a>

  1560. can be used to directly manage when the accumulated headers are sent.

  1561. (Contributed by Andrew Schaaf in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3709">bpo-3709</a>.)</p>

  1562. <p><a class="reference internal" href="../library/http.server.html#module-http.server" title="http.server: HTTP server and request handlers."><code class="xref py py-class docutils literal notranslate"><span class="pre">http.server</span></code></a> now produces valid <code class="docutils literal notranslate"><span class="pre">HTML</span> <span class="pre">4.01</span> <span class="pre">strict</span></code> output.

  1563. (Contributed by Ezio Melotti in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13295">bpo-13295</a>.)</p>

  1564. <p><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">http.client.HTTPResponse</span></code></a> now has a

  1565. <a class="reference internal" href="../library/http.client.html#http.client.HTTPResponse.readinto" title="http.client.HTTPResponse.readinto"><code class="xref py py-meth docutils literal notranslate"><span class="pre">readinto()</span></code></a> method, which means it can be used

  1566. as an <a class="reference internal" href="../library/io.html#io.RawIOBase" title="io.RawIOBase"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.RawIOBase</span></code></a> class.  (Contributed by John Kuhn in

  1567. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13464">bpo-13464</a>.)</p>

  1568. </section>

  1569. <section id="html">

  1570. <h3>html<a class="headerlink" href="#html" title="Link to this heading">¶</a></h3>

  1571. <p><a class="reference internal" href="../library/html.parser.html#html.parser.HTMLParser" title="html.parser.HTMLParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">html.parser.HTMLParser</span></code></a> is now able to parse broken markup without

  1572. raising errors, therefore the <em>strict</em> argument of the constructor and the

  1573. <code class="xref py py-exc docutils literal notranslate"><span class="pre">HTMLParseError</span></code> exception are now deprecated.

  1574. The ability to parse broken markup is the result of a number of bug fixes that

  1575. are also available on the latest bug fix releases of Python 2.7/3.2.

  1576. (Contributed by Ezio Melotti in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=15114">bpo-15114</a>, and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14538">bpo-14538</a>,

  1577. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13993">bpo-13993</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13960">bpo-13960</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13358">bpo-13358</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1745761">bpo-1745761</a>,

  1578. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=755670">bpo-755670</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13357">bpo-13357</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12629">bpo-12629</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1200313">bpo-1200313</a>,

  1579. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=670664">bpo-670664</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13273">bpo-13273</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12888">bpo-12888</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=7311">bpo-7311</a>.)</p>

  1580. <p>A new <a class="reference internal" href="../library/html.entities.html#html.entities.html5" title="html.entities.html5"><code class="xref py py-data docutils literal notranslate"><span class="pre">html5</span></code></a> dictionary that maps HTML5 named character

  1581. references to the equivalent Unicode character(s) (e.g. <code class="docutils literal notranslate"><span class="pre">html5['gt;']</span> <span class="pre">==</span>

  1582. <span class="pre">'&gt;'</span></code>) has been added to the <a class="reference internal" href="../library/html.entities.html#module-html.entities" title="html.entities: Definitions of HTML general entities."><code class="xref py py-mod docutils literal notranslate"><span class="pre">html.entities</span></code></a> module.  The dictionary is

  1583. now also used by <a class="reference internal" href="../library/html.parser.html#html.parser.HTMLParser" title="html.parser.HTMLParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">HTMLParser</span></code></a>.  (Contributed by Ezio

  1584. Melotti in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11113">bpo-11113</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=15156">bpo-15156</a>.)</p>

  1585. </section>

  1586. <section id="imaplib">

  1587. <h3>imaplib<a class="headerlink" href="#imaplib" title="Link to this heading">¶</a></h3>

  1588. <p>The <a class="reference internal" href="../library/imaplib.html#imaplib.IMAP4_SSL" title="imaplib.IMAP4_SSL"><code class="xref py py-class docutils literal notranslate"><span class="pre">IMAP4_SSL</span></code></a> constructor now accepts an SSLContext

  1589. parameter to control parameters of the secure channel.</p>

  1590. <p>(Contributed by Sijin Joseph in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8808">bpo-8808</a>.)</p>

  1591. </section>

  1592. <section id="inspect">

  1593. <h3>inspect<a class="headerlink" href="#inspect" title="Link to this heading">¶</a></h3>

  1594. <p>A new <a class="reference internal" href="../library/inspect.html#inspect.getclosurevars" title="inspect.getclosurevars"><code class="xref py py-func docutils literal notranslate"><span class="pre">getclosurevars()</span></code></a> function has been added. This function

  1595. reports the current binding of all names referenced from the function body and

  1596. where those names were resolved, making it easier to verify correct internal

  1597. state when testing code that relies on stateful closures.</p>

  1598. <p>(Contributed by Meador Inge and Nick Coghlan in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13062">bpo-13062</a>.)</p>

  1599. <p>A new <a class="reference internal" href="../library/inspect.html#inspect.getgeneratorlocals" title="inspect.getgeneratorlocals"><code class="xref py py-func docutils literal notranslate"><span class="pre">getgeneratorlocals()</span></code></a> function has been added. This

  1600. function reports the current binding of local variables in the generator’s

  1601. stack frame, making it easier to verify correct internal state when testing

  1602. generators.</p>

  1603. <p>(Contributed by Meador Inge in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=15153">bpo-15153</a>.)</p>

  1604. </section>

  1605. <section id="io">

  1606. <h3>io<a class="headerlink" href="#io" title="Link to this heading">¶</a></h3>

  1607. <p>The <a class="reference internal" href="../library/io.html#io.open" title="io.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">open()</span></code></a> function has a new <code class="docutils literal notranslate"><span class="pre">'x'</span></code> mode that can be used to

  1608. exclusively create a new file, and raise a <a class="reference internal" href="../library/exceptions.html#FileExistsError" title="FileExistsError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">FileExistsError</span></code></a> if the file

  1609. already exists. It is based on the C11 ‘x’ mode to fopen().</p>

  1610. <p>(Contributed by David Townshend in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12760">bpo-12760</a>.)</p>

  1611. <p>The constructor of the <a class="reference internal" href="../library/io.html#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">TextIOWrapper</span></code></a> class has a new

  1612. <em>write_through</em> optional argument. If <em>write_through</em> is <code class="docutils literal notranslate"><span class="pre">True</span></code>, calls to

  1613. <code class="xref py py-meth docutils literal notranslate"><span class="pre">write()</span></code> are guaranteed not to be buffered: any data

  1614. written on the <a class="reference internal" href="../library/io.html#io.TextIOWrapper" title="io.TextIOWrapper"><code class="xref py py-class docutils literal notranslate"><span class="pre">TextIOWrapper</span></code></a> object is immediately handled to its

  1615. underlying binary buffer.</p>

  1616. </section>

  1617. <section id="itertools">

  1618. <h3>itertools<a class="headerlink" href="#itertools" title="Link to this heading">¶</a></h3>

  1619. <p><a class="reference internal" href="../library/itertools.html#itertools.accumulate" title="itertools.accumulate"><code class="xref py py-func docutils literal notranslate"><span class="pre">accumulate()</span></code></a> now takes an optional <code class="docutils literal notranslate"><span class="pre">func</span></code> argument for

  1620. providing a user-supplied binary function.</p>

  1621. </section>

  1622. <section id="logging">

  1623. <h3>logging<a class="headerlink" href="#logging" title="Link to this heading">¶</a></h3>

  1624. <p>The <a class="reference internal" href="../library/logging.html#logging.basicConfig" title="logging.basicConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">basicConfig()</span></code></a> function now supports an optional <code class="docutils literal notranslate"><span class="pre">handlers</span></code>

  1625. argument taking an iterable of handlers to be added to the root logger.</p>

  1626. <p>A class level attribute <code class="xref py py-attr docutils literal notranslate"><span class="pre">append_nul</span></code> has

  1627. been added to <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> to allow control of the

  1628. appending of the <code class="docutils literal notranslate"><span class="pre">NUL</span></code> (<code class="docutils literal notranslate"><span class="pre">\000</span></code>) byte to syslog records, since for some

  1629. daemons it is required while for others it is passed through to the log.</p>

  1630. </section>

  1631. <section id="math">

  1632. <h3>math<a class="headerlink" href="#math" title="Link to this heading">¶</a></h3>

  1633. <p>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 has a new function, <a class="reference internal" href="../library/math.html#math.log2" title="math.log2"><code class="xref py py-func docutils literal notranslate"><span class="pre">log2()</span></code></a>,  which returns

  1634. the base-2 logarithm of <em>x</em>.</p>

  1635. <p>(Written by Mark Dickinson in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11888">bpo-11888</a>.)</p>

  1636. </section>

  1637. <section id="mmap">

  1638. <h3>mmap<a class="headerlink" href="#mmap" title="Link to this heading">¶</a></h3>

  1639. <p>The <a class="reference internal" href="../library/mmap.html#mmap.mmap.read" title="mmap.mmap.read"><code class="xref py py-meth docutils literal notranslate"><span class="pre">read()</span></code></a> method is now more compatible with other file-like

  1640. objects: if the argument is omitted or specified as <code class="docutils literal notranslate"><span class="pre">None</span></code>, it returns the

  1641. bytes from the current file position to the end of the mapping.  (Contributed

  1642. by Petri Lehtinen in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12021">bpo-12021</a>.)</p>

  1643. </section>

  1644. <section id="multiprocessing">

  1645. <h3>multiprocessing<a class="headerlink" href="#multiprocessing" title="Link to this heading">¶</a></h3>

  1646. <p>The new <a class="reference internal" href="../library/multiprocessing.html#multiprocessing.connection.wait" title="multiprocessing.connection.wait"><code class="xref py py-func docutils literal notranslate"><span class="pre">multiprocessing.connection.wait()</span></code></a> function allows polling

  1647. multiple objects (such as connections, sockets and pipes) with a timeout.

  1648. (Contributed by Richard Oudkerk in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12328">bpo-12328</a>.)</p>

  1649. <p><code class="xref py py-class docutils literal notranslate"><span class="pre">multiprocessing.Connection</span></code> objects can now be transferred over

  1650. multiprocessing connections.

  1651. (Contributed by Richard Oudkerk in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4892">bpo-4892</a>.)</p>

  1652. <p><a class="reference internal" href="../library/multiprocessing.html#multiprocessing.Process" title="multiprocessing.Process"><code class="xref py py-class docutils literal notranslate"><span class="pre">multiprocessing.Process</span></code></a> now accepts a <code class="docutils literal notranslate"><span class="pre">daemon</span></code> keyword argument

  1653. to override the default behavior of inheriting the <code class="docutils literal notranslate"><span class="pre">daemon</span></code> flag from

  1654. the parent process (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6064">bpo-6064</a>).</p>

  1655. <p>New attribute <a class="reference internal" href="../library/multiprocessing.html#multiprocessing.Process.sentinel" title="multiprocessing.Process.sentinel"><code class="xref py py-data docutils literal notranslate"><span class="pre">multiprocessing.Process.sentinel</span></code></a> allows a

  1656. program to wait on multiple <a class="reference internal" href="../library/multiprocessing.html#multiprocessing.Process" title="multiprocessing.Process"><code class="xref py py-class docutils literal notranslate"><span class="pre">Process</span></code></a> objects at one

  1657. time using the appropriate OS primitives (for example, <a class="reference internal" href="../library/select.html#module-select" title="select: Wait for I/O completion on multiple streams."><code class="xref py py-mod docutils literal notranslate"><span class="pre">select</span></code></a> on

  1658. posix systems).</p>

  1659. <p>New methods <a class="reference internal" href="../library/multiprocessing.html#multiprocessing.pool.Pool.starmap" title="multiprocessing.pool.Pool.starmap"><code class="xref py py-meth docutils literal notranslate"><span class="pre">multiprocessing.pool.Pool.starmap()</span></code></a> and

  1660. <a class="reference internal" href="../library/multiprocessing.html#multiprocessing.pool.Pool.starmap_async" title="multiprocessing.pool.Pool.starmap_async"><code class="xref py py-meth docutils literal notranslate"><span class="pre">starmap_async()</span></code></a> provide

  1661. <a class="reference internal" href="../library/itertools.html#itertools.starmap" title="itertools.starmap"><code class="xref py py-func docutils literal notranslate"><span class="pre">itertools.starmap()</span></code></a> equivalents to the existing

  1662. <a class="reference internal" href="../library/multiprocessing.html#multiprocessing.pool.Pool.map" title="multiprocessing.pool.Pool.map"><code class="xref py py-meth docutils literal notranslate"><span class="pre">multiprocessing.pool.Pool.map()</span></code></a> and

  1663. <a class="reference internal" href="../library/multiprocessing.html#multiprocessing.pool.Pool.map_async" title="multiprocessing.pool.Pool.map_async"><code class="xref py py-meth docutils literal notranslate"><span class="pre">map_async()</span></code></a> functions.  (Contributed by Hynek

  1664. Schlawack in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12708">bpo-12708</a>.)</p>

  1665. </section>

  1666. <section id="nntplib">

  1667. <h3>nntplib<a class="headerlink" href="#nntplib" title="Link to this heading">¶</a></h3>

  1668. <p>The <a class="reference internal" href="../library/nntplib.html#nntplib.NNTP" title="nntplib.NNTP"><code class="xref py py-class docutils literal notranslate"><span class="pre">nntplib.NNTP</span></code></a> class now supports the context management protocol to

  1669. unconditionally consume <a class="reference internal" href="../library/socket.html#socket.error" title="socket.error"><code class="xref py py-exc docutils literal notranslate"><span class="pre">socket.error</span></code></a> exceptions and to close the NNTP

  1670. connection when done:</p>

  1671. <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">nntplib</span> <span class="kn">import</span> <span class="n">NNTP</span>

  1672. <span class="gp">&gt;&gt;&gt; </span><span class="k">with</span> <span class="n">NNTP</span><span class="p">(</span><span class="s1">&#39;news.gmane.org&#39;</span><span class="p">)</span> <span class="k">as</span> <span class="n">n</span><span class="p">:</span>

  1673. <span class="gp">... </span>    <span class="n">n</span><span class="o">.</span><span class="n">group</span><span class="p">(</span><span class="s1">&#39;gmane.comp.python.committers&#39;</span><span class="p">)</span>

  1674. <span class="gp">...</span>

  1675. <span class="go">(&#39;211 1755 1 1755 gmane.comp.python.committers&#39;, 1755, 1, 1755, &#39;gmane.comp.python.committers&#39;)</span>

  1676. <span class="gp">&gt;&gt;&gt;</span>

  1677. </pre></div>

  1678. </div>

  1679. <p>(Contributed by Giampaolo Rodolà in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=9795">bpo-9795</a>.)</p>

  1680. </section>

  1681. <section id="os">

  1682. <h3>os<a class="headerlink" href="#os" title="Link to this heading">¶</a></h3>

  1683. <ul>

  1684. <li><p>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 has a new <a class="reference internal" href="../library/os.html#os.pipe2" title="os.pipe2"><code class="xref py py-func docutils literal notranslate"><span class="pre">pipe2()</span></code></a> function that makes it

  1685. possible to create a pipe with <a class="reference internal" href="../library/os.html#os.O_CLOEXEC" title="os.O_CLOEXEC"><code class="xref py py-const docutils literal notranslate"><span class="pre">O_CLOEXEC</span></code></a> or

  1686. <a class="reference internal" href="../library/os.html#os.O_NONBLOCK" title="os.O_NONBLOCK"><code class="xref py py-const docutils literal notranslate"><span class="pre">O_NONBLOCK</span></code></a> flags set atomically. This is especially useful to

  1687. avoid race conditions in multi-threaded programs.</p></li>

  1688. <li><p>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 has a new <a class="reference internal" href="../library/os.html#os.sendfile" title="os.sendfile"><code class="xref py py-func docutils literal notranslate"><span class="pre">sendfile()</span></code></a> function which provides

  1689. an efficient “zero-copy” way for copying data from one file (or socket)

  1690. descriptor to another. The phrase “zero-copy” refers to the fact that all of

  1691. the copying of data between the two descriptors is done entirely by the

  1692. kernel, with no copying of data into userspace buffers. <a class="reference internal" href="../library/os.html#os.sendfile" title="os.sendfile"><code class="xref py py-func docutils literal notranslate"><span class="pre">sendfile()</span></code></a>

  1693. can be used to efficiently copy data from a file on disk to a network socket,

  1694. e.g. for downloading a file.</p>

  1695. <p>(Patch submitted by Ross Lagerwall and Giampaolo Rodolà in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10882">bpo-10882</a>.)</p>

  1696. </li>

  1697. <li><p>To avoid race conditions like symlink attacks and issues with temporary

  1698. files and directories, it is more reliable (and also faster) to manipulate

  1699. file descriptors instead of file names. Python 3.3 enhances existing functions

  1700. and introduces new functions to work on file descriptors (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4761">bpo-4761</a>,

  1701. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10755">bpo-10755</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14626">bpo-14626</a>).</p>

  1702. <ul class="simple">

  1703. <li><p>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 has a new <a class="reference internal" href="../library/os.html#os.fwalk" title="os.fwalk"><code class="xref py py-func docutils literal notranslate"><span class="pre">fwalk()</span></code></a> function similar to

  1704. <a class="reference internal" href="../library/os.html#os.walk" title="os.walk"><code class="xref py py-func docutils literal notranslate"><span class="pre">walk()</span></code></a> except that it also yields file descriptors referring to the

  1705. directories visited. This is especially useful to avoid symlink races.</p></li>

  1706. <li><p>The following functions get new optional <em>dir_fd</em> (<a class="reference internal" href="../library/os.html#dir-fd"><span class="std std-ref">paths relative to

  1707. directory descriptors</span></a>) and/or <em>follow_symlinks</em> (<a class="reference internal" href="../library/os.html#follow-symlinks"><span class="std std-ref">not

  1708. following symlinks</span></a>):

  1709. <a class="reference internal" href="../library/os.html#os.access" title="os.access"><code class="xref py py-func docutils literal notranslate"><span class="pre">access()</span></code></a>, <a class="reference internal" href="../library/os.html#os.chflags" title="os.chflags"><code class="xref py py-func docutils literal notranslate"><span class="pre">chflags()</span></code></a>, <a class="reference internal" href="../library/os.html#os.chmod" title="os.chmod"><code class="xref py py-func docutils literal notranslate"><span class="pre">chmod()</span></code></a>, <a class="reference internal" href="../library/os.html#os.chown" title="os.chown"><code class="xref py py-func docutils literal notranslate"><span class="pre">chown()</span></code></a>,

  1710. <a class="reference internal" href="../library/os.html#os.link" title="os.link"><code class="xref py py-func docutils literal notranslate"><span class="pre">link()</span></code></a>, <a class="reference internal" href="../library/os.html#os.lstat" title="os.lstat"><code class="xref py py-func docutils literal notranslate"><span class="pre">lstat()</span></code></a>, <a class="reference internal" href="../library/os.html#os.mkdir" title="os.mkdir"><code class="xref py py-func docutils literal notranslate"><span class="pre">mkdir()</span></code></a>, <a class="reference internal" href="../library/os.html#os.mkfifo" title="os.mkfifo"><code class="xref py py-func docutils literal notranslate"><span class="pre">mkfifo()</span></code></a>,

  1711. <a class="reference internal" href="../library/os.html#os.mknod" title="os.mknod"><code class="xref py py-func docutils literal notranslate"><span class="pre">mknod()</span></code></a>, <a class="reference internal" href="../library/os.html#os.open" title="os.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">open()</span></code></a>, <a class="reference internal" href="../library/os.html#os.readlink" title="os.readlink"><code class="xref py py-func docutils literal notranslate"><span class="pre">readlink()</span></code></a>, <a class="reference internal" href="../library/os.html#os.remove" title="os.remove"><code class="xref py py-func docutils literal notranslate"><span class="pre">remove()</span></code></a>,

  1712. <a class="reference internal" href="../library/os.html#os.rename" title="os.rename"><code class="xref py py-func docutils literal notranslate"><span class="pre">rename()</span></code></a>, <a class="reference internal" href="../library/os.html#os.replace" title="os.replace"><code class="xref py py-func docutils literal notranslate"><span class="pre">replace()</span></code></a>, <a class="reference internal" href="../library/os.html#os.rmdir" title="os.rmdir"><code class="xref py py-func docutils literal notranslate"><span class="pre">rmdir()</span></code></a>, <a class="reference internal" href="../library/os.html#os.stat" title="os.stat"><code class="xref py py-func docutils literal notranslate"><span class="pre">stat()</span></code></a>,

  1713. <a class="reference internal" href="../library/os.html#os.symlink" title="os.symlink"><code class="xref py py-func docutils literal notranslate"><span class="pre">symlink()</span></code></a>, <a class="reference internal" href="../library/os.html#os.unlink" title="os.unlink"><code class="xref py py-func docutils literal notranslate"><span class="pre">unlink()</span></code></a>, <a class="reference internal" href="../library/os.html#os.utime" title="os.utime"><code class="xref py py-func docutils literal notranslate"><span class="pre">utime()</span></code></a>.  Platform

  1714. support for using these parameters can be checked via the sets

  1715. <a class="reference internal" href="../library/os.html#os.supports_dir_fd" title="os.supports_dir_fd"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.supports_dir_fd</span></code></a> and <code class="xref py py-data docutils literal notranslate"><span class="pre">os.supports_follows_symlinks</span></code>.</p></li>

  1716. <li><p>The following functions now support a file descriptor for their path argument:

  1717. <a class="reference internal" href="../library/os.html#os.chdir" title="os.chdir"><code class="xref py py-func docutils literal notranslate"><span class="pre">chdir()</span></code></a>, <a class="reference internal" href="../library/os.html#os.chmod" title="os.chmod"><code class="xref py py-func docutils literal notranslate"><span class="pre">chmod()</span></code></a>, <a class="reference internal" href="../library/os.html#os.chown" title="os.chown"><code class="xref py py-func docutils literal notranslate"><span class="pre">chown()</span></code></a>,

  1718. <a class="reference internal" href="../library/os.html#os.execve" title="os.execve"><code class="xref py py-func docutils literal notranslate"><span class="pre">execve()</span></code></a>, <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">listdir()</span></code></a>, <a class="reference internal" href="../library/os.html#os.pathconf" title="os.pathconf"><code class="xref py py-func docutils literal notranslate"><span class="pre">pathconf()</span></code></a>, <a class="reference internal" href="../library/os.path.html#os.path.exists" title="os.path.exists"><code class="xref py py-func docutils literal notranslate"><span class="pre">exists()</span></code></a>,

  1719. <a class="reference internal" href="../library/os.html#os.stat" title="os.stat"><code class="xref py py-func docutils literal notranslate"><span class="pre">stat()</span></code></a>, <a class="reference internal" href="../library/os.html#os.statvfs" title="os.statvfs"><code class="xref py py-func docutils literal notranslate"><span class="pre">statvfs()</span></code></a>, <a class="reference internal" href="../library/os.html#os.utime" title="os.utime"><code class="xref py py-func docutils literal notranslate"><span class="pre">utime()</span></code></a>.  Platform support

  1720. for this can be checked via the <a class="reference internal" href="../library/os.html#os.supports_fd" title="os.supports_fd"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.supports_fd</span></code></a> set.</p></li>

  1721. </ul>

  1722. </li>

  1723. <li><p><a class="reference internal" href="../library/os.html#os.access" title="os.access"><code class="xref py py-func docutils literal notranslate"><span class="pre">access()</span></code></a> accepts an <code class="docutils literal notranslate"><span class="pre">effective_ids</span></code> keyword argument to turn on

  1724. using the effective uid/gid rather than the real uid/gid in the access check.

  1725. Platform support for this can be checked via the

  1726. <a class="reference internal" href="../library/os.html#os.supports_effective_ids" title="os.supports_effective_ids"><code class="xref py py-data docutils literal notranslate"><span class="pre">supports_effective_ids</span></code></a> set.</p></li>

  1727. <li><p>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 has two new functions: <a class="reference internal" href="../library/os.html#os.getpriority" title="os.getpriority"><code class="xref py py-func docutils literal notranslate"><span class="pre">getpriority()</span></code></a> and

  1728. <a class="reference internal" href="../library/os.html#os.setpriority" title="os.setpriority"><code class="xref py py-func docutils literal notranslate"><span class="pre">setpriority()</span></code></a>. They can be used to get or set process

  1729. niceness/priority in a fashion similar to <a class="reference internal" href="../library/os.html#os.nice" title="os.nice"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.nice()</span></code></a> but extended to all

  1730. processes instead of just the current one.</p>

  1731. <p>(Patch submitted by Giampaolo Rodolà in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10784">bpo-10784</a>.)</p>

  1732. </li>

  1733. <li><p>The new <a class="reference internal" href="../library/os.html#os.replace" title="os.replace"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.replace()</span></code></a> function allows cross-platform renaming of a

  1734. file with overwriting the destination.  With <a class="reference internal" href="../library/os.html#os.rename" title="os.rename"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.rename()</span></code></a>, an existing

  1735. destination file is overwritten under POSIX, but raises an error under

  1736. Windows.

  1737. (Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8828">bpo-8828</a>.)</p></li>

  1738. <li><p>The stat family of functions (<a class="reference internal" href="../library/os.html#os.stat" title="os.stat"><code class="xref py py-func docutils literal notranslate"><span class="pre">stat()</span></code></a>, <a class="reference internal" href="../library/os.html#os.fstat" title="os.fstat"><code class="xref py py-func docutils literal notranslate"><span class="pre">fstat()</span></code></a>,

  1739. and <a class="reference internal" href="../library/os.html#os.lstat" title="os.lstat"><code class="xref py py-func docutils literal notranslate"><span class="pre">lstat()</span></code></a>) now support reading a file’s timestamps

  1740. with nanosecond precision.  Symmetrically, <a class="reference internal" href="../library/os.html#os.utime" title="os.utime"><code class="xref py py-func docutils literal notranslate"><span class="pre">utime()</span></code></a>

  1741. can now write file timestamps with nanosecond precision.  (Contributed by

  1742. Larry Hastings in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14127">bpo-14127</a>.)</p></li>

  1743. <li><p>The new <a class="reference internal" href="../library/os.html#os.get_terminal_size" title="os.get_terminal_size"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.get_terminal_size()</span></code></a> function queries the size of the

  1744. terminal attached to a file descriptor. See also

  1745. <a class="reference internal" href="../library/shutil.html#shutil.get_terminal_size" title="shutil.get_terminal_size"><code class="xref py py-func docutils literal notranslate"><span class="pre">shutil.get_terminal_size()</span></code></a>.

  1746. (Contributed by Zbigniew Jędrzejewski-Szmek in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13609">bpo-13609</a>.)</p></li>

  1747. </ul>

  1748. <ul class="simple">

  1749. <li><p>New functions to support Linux extended attributes (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12720">bpo-12720</a>):

  1750. <a class="reference internal" href="../library/os.html#os.getxattr" title="os.getxattr"><code class="xref py py-func docutils literal notranslate"><span class="pre">getxattr()</span></code></a>, <a class="reference internal" href="../library/os.html#os.listxattr" title="os.listxattr"><code class="xref py py-func docutils literal notranslate"><span class="pre">listxattr()</span></code></a>, <a class="reference internal" href="../library/os.html#os.removexattr" title="os.removexattr"><code class="xref py py-func docutils literal notranslate"><span class="pre">removexattr()</span></code></a>,

  1751. <a class="reference internal" href="../library/os.html#os.setxattr" title="os.setxattr"><code class="xref py py-func docutils literal notranslate"><span class="pre">setxattr()</span></code></a>.</p></li>

  1752. <li><p>New interface to the scheduler. These functions

  1753. control how a process is allocated CPU time by the operating system. New

  1754. functions:

  1755. <a class="reference internal" href="../library/os.html#os.sched_get_priority_max" title="os.sched_get_priority_max"><code class="xref py py-func docutils literal notranslate"><span class="pre">sched_get_priority_max()</span></code></a>, <a class="reference internal" href="../library/os.html#os.sched_get_priority_min" title="os.sched_get_priority_min"><code class="xref py py-func docutils literal notranslate"><span class="pre">sched_get_priority_min()</span></code></a>,

  1756. <a class="reference internal" href="../library/os.html#os.sched_getaffinity" title="os.sched_getaffinity"><code class="xref py py-func docutils literal notranslate"><span class="pre">sched_getaffinity()</span></code></a>, <a class="reference internal" href="../library/os.html#os.sched_getparam" title="os.sched_getparam"><code class="xref py py-func docutils literal notranslate"><span class="pre">sched_getparam()</span></code></a>,

  1757. <a class="reference internal" href="../library/os.html#os.sched_getscheduler" title="os.sched_getscheduler"><code class="xref py py-func docutils literal notranslate"><span class="pre">sched_getscheduler()</span></code></a>, <a class="reference internal" href="../library/os.html#os.sched_rr_get_interval" title="os.sched_rr_get_interval"><code class="xref py py-func docutils literal notranslate"><span class="pre">sched_rr_get_interval()</span></code></a>,

  1758. <a class="reference internal" href="../library/os.html#os.sched_setaffinity" title="os.sched_setaffinity"><code class="xref py py-func docutils literal notranslate"><span class="pre">sched_setaffinity()</span></code></a>, <a class="reference internal" href="../library/os.html#os.sched_setparam" title="os.sched_setparam"><code class="xref py py-func docutils literal notranslate"><span class="pre">sched_setparam()</span></code></a>,

  1759. <a class="reference internal" href="../library/os.html#os.sched_setscheduler" title="os.sched_setscheduler"><code class="xref py py-func docutils literal notranslate"><span class="pre">sched_setscheduler()</span></code></a>, <a class="reference internal" href="../library/os.html#os.sched_yield" title="os.sched_yield"><code class="xref py py-func docutils literal notranslate"><span class="pre">sched_yield()</span></code></a>,</p></li>

  1760. <li><p>New functions to control the file system:</p>

  1761. <ul>

  1762. <li><p><a class="reference internal" href="../library/os.html#os.posix_fadvise" title="os.posix_fadvise"><code class="xref py py-func docutils literal notranslate"><span class="pre">posix_fadvise()</span></code></a>: Announces an intention to access data in a

  1763. specific pattern thus allowing the kernel to make optimizations.</p></li>

  1764. <li><p><a class="reference internal" href="../library/os.html#os.posix_fallocate" title="os.posix_fallocate"><code class="xref py py-func docutils literal notranslate"><span class="pre">posix_fallocate()</span></code></a>: Ensures that enough disk space is allocated

  1765. for a file.</p></li>

  1766. <li><p><a class="reference internal" href="../library/os.html#os.sync" title="os.sync"><code class="xref py py-func docutils literal notranslate"><span class="pre">sync()</span></code></a>: Force write of everything to disk.</p></li>

  1767. </ul>

  1768. </li>

  1769. <li><p>Additional new  posix functions:</p>

  1770. <ul>

  1771. <li><p><a class="reference internal" href="../library/os.html#os.lockf" title="os.lockf"><code class="xref py py-func docutils literal notranslate"><span class="pre">lockf()</span></code></a>: Apply, test or remove a POSIX lock on an open file descriptor.</p></li>

  1772. <li><p><a class="reference internal" href="../library/os.html#os.pread" title="os.pread"><code class="xref py py-func docutils literal notranslate"><span class="pre">pread()</span></code></a>: Read from a file descriptor at an offset, the file

  1773. offset remains unchanged.</p></li>

  1774. <li><p><a class="reference internal" href="../library/os.html#os.pwrite" title="os.pwrite"><code class="xref py py-func docutils literal notranslate"><span class="pre">pwrite()</span></code></a>: Write to a file descriptor from an offset, leaving

  1775. the file offset unchanged.</p></li>

  1776. <li><p><a class="reference internal" href="../library/os.html#os.readv" title="os.readv"><code class="xref py py-func docutils literal notranslate"><span class="pre">readv()</span></code></a>: Read from a file descriptor into a number of writable buffers.</p></li>

  1777. <li><p><a class="reference internal" href="../library/os.html#os.truncate" title="os.truncate"><code class="xref py py-func docutils literal notranslate"><span class="pre">truncate()</span></code></a>: Truncate the file corresponding to <em>path</em>, so that

  1778. it is at most <em>length</em> bytes in size.</p></li>

  1779. <li><p><a class="reference internal" href="../library/os.html#os.waitid" title="os.waitid"><code class="xref py py-func docutils literal notranslate"><span class="pre">waitid()</span></code></a>: Wait for the completion of one or more child processes.</p></li>

  1780. <li><p><a class="reference internal" href="../library/os.html#os.writev" title="os.writev"><code class="xref py py-func docutils literal notranslate"><span class="pre">writev()</span></code></a>: Write the contents of <em>buffers</em> to a file descriptor,

  1781. where <em>buffers</em> is an arbitrary sequence of buffers.</p></li>

  1782. <li><p><a class="reference internal" href="../library/os.html#os.getgrouplist" title="os.getgrouplist"><code class="xref py py-func docutils literal notranslate"><span class="pre">getgrouplist()</span></code></a> (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=9344">bpo-9344</a>): Return list of group ids that

  1783. specified user belongs to.</p></li>

  1784. </ul>

  1785. </li>

  1786. <li><p><a class="reference internal" href="../library/os.html#os.times" title="os.times"><code class="xref py py-func docutils literal notranslate"><span class="pre">times()</span></code></a> and <a class="reference internal" href="../library/os.html#os.uname" title="os.uname"><code class="xref py py-func docutils literal notranslate"><span class="pre">uname()</span></code></a>: Return type changed from a tuple to

  1787. a tuple-like object with named attributes.</p></li>

  1788. <li><p>Some platforms now support additional constants for the <a class="reference internal" href="../library/os.html#os.lseek" title="os.lseek"><code class="xref py py-func docutils literal notranslate"><span class="pre">lseek()</span></code></a>

  1789. function, such as <code class="docutils literal notranslate"><span class="pre">os.SEEK_HOLE</span></code> and <code class="docutils literal notranslate"><span class="pre">os.SEEK_DATA</span></code>.</p></li>

  1790. <li><p>New constants <a class="reference internal" href="../library/os.html#os.RTLD_LAZY" title="os.RTLD_LAZY"><code class="xref py py-const docutils literal notranslate"><span class="pre">RTLD_LAZY</span></code></a>, <a class="reference internal" href="../library/os.html#os.RTLD_NOW" title="os.RTLD_NOW"><code class="xref py py-const docutils literal notranslate"><span class="pre">RTLD_NOW</span></code></a>,

  1791. <a class="reference internal" href="../library/os.html#os.RTLD_GLOBAL" title="os.RTLD_GLOBAL"><code class="xref py py-const docutils literal notranslate"><span class="pre">RTLD_GLOBAL</span></code></a>, <a class="reference internal" href="../library/os.html#os.RTLD_LOCAL" title="os.RTLD_LOCAL"><code class="xref py py-const docutils literal notranslate"><span class="pre">RTLD_LOCAL</span></code></a>, <a class="reference internal" href="../library/os.html#os.RTLD_NODELETE" title="os.RTLD_NODELETE"><code class="xref py py-const docutils literal notranslate"><span class="pre">RTLD_NODELETE</span></code></a>,

  1792. <a class="reference internal" href="../library/os.html#os.RTLD_NOLOAD" title="os.RTLD_NOLOAD"><code class="xref py py-const docutils literal notranslate"><span class="pre">RTLD_NOLOAD</span></code></a>, and <a class="reference internal" href="../library/os.html#os.RTLD_DEEPBIND" title="os.RTLD_DEEPBIND"><code class="xref py py-const docutils literal notranslate"><span class="pre">RTLD_DEEPBIND</span></code></a> are available on

  1793. platforms that support them.   These are for use with the

  1794. <a class="reference internal" href="../library/sys.html#sys.setdlopenflags" title="sys.setdlopenflags"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.setdlopenflags()</span></code></a> function, and supersede the similar constants

  1795. defined in <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> and <code class="xref py py-mod docutils literal notranslate"><span class="pre">DLFCN</span></code>.  (Contributed by Victor Stinner

  1796. in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13226">bpo-13226</a>.)</p></li>

  1797. <li><p><a class="reference internal" href="../library/os.html#os.symlink" title="os.symlink"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.symlink()</span></code></a> now accepts (and ignores) the <code class="docutils literal notranslate"><span class="pre">target_is_directory</span></code>

  1798. keyword argument on non-Windows platforms, to ease cross-platform support.</p></li>

  1799. </ul>

  1800. </section>

  1801. <section id="pdb">

  1802. <h3>pdb<a class="headerlink" href="#pdb" title="Link to this heading">¶</a></h3>

  1803. <p>Tab-completion is now available not only for command names, but also their

  1804. arguments.  For example, for the <code class="docutils literal notranslate"><span class="pre">break</span></code> command, function and file names

  1805. are completed.</p>

  1806. <p>(Contributed by Georg Brandl in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14210">bpo-14210</a>)</p>

  1807. </section>

  1808. <section id="pickle">

  1809. <h3>pickle<a class="headerlink" href="#pickle" title="Link to this heading">¶</a></h3>

  1810. <p><a class="reference internal" href="../library/pickle.html#pickle.Pickler" title="pickle.Pickler"><code class="xref py py-class docutils literal notranslate"><span class="pre">pickle.Pickler</span></code></a> objects now have an optional

  1811. <a class="reference internal" href="../library/pickle.html#pickle.Pickler.dispatch_table" title="pickle.Pickler.dispatch_table"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dispatch_table</span></code></a> attribute allowing per-pickler

  1812. reduction functions to be set.</p>

  1813. <p>(Contributed by Richard Oudkerk in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14166">bpo-14166</a>.)</p>

  1814. </section>

  1815. <section id="pydoc">

  1816. <h3>pydoc<a class="headerlink" href="#pydoc" title="Link to this heading">¶</a></h3>

  1817. <p>The Tk GUI and the <code class="xref py py-func docutils literal notranslate"><span class="pre">serve()</span></code> function have been removed from the

  1818. <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: <code class="docutils literal notranslate"><span class="pre">pydoc</span> <span class="pre">-g</span></code> and <code class="xref py py-func docutils literal notranslate"><span class="pre">serve()</span></code> have been deprecated

  1819. in Python 3.2.</p>

  1820. </section>

  1821. <section id="re">

  1822. <h3>re<a class="headerlink" href="#re" title="Link to this heading">¶</a></h3>

  1823. <p><a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> regular expressions now support <code class="docutils literal notranslate"><span class="pre">\u</span></code> and <code class="docutils literal notranslate"><span class="pre">\U</span></code> escapes.</p>

  1824. <p>(Contributed by Serhiy Storchaka in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3665">bpo-3665</a>.)</p>

  1825. </section>

  1826. <section id="sched">

  1827. <h3>sched<a class="headerlink" href="#sched" title="Link to this heading">¶</a></h3>

  1828. <ul class="simple">

  1829. <li><p><a class="reference internal" href="../library/sched.html#sched.scheduler.run" title="sched.scheduler.run"><code class="xref py py-meth docutils literal notranslate"><span class="pre">run()</span></code></a> now accepts a <em>blocking</em> parameter which when

  1830. set to false makes the method execute the scheduled events due to expire

  1831. soonest (if any) and then return immediately.

  1832. This is useful in case you want to use the <a class="reference internal" href="../library/sched.html#sched.scheduler" title="sched.scheduler"><code class="xref py py-class docutils literal notranslate"><span class="pre">scheduler</span></code></a> in

  1833. non-blocking applications.  (Contributed by Giampaolo Rodolà in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13449">bpo-13449</a>.)</p></li>

  1834. <li><p><a class="reference internal" href="../library/sched.html#sched.scheduler" title="sched.scheduler"><code class="xref py py-class docutils literal notranslate"><span class="pre">scheduler</span></code></a> class can now be safely used in multi-threaded

  1835. environments.  (Contributed by Josiah Carlson and Giampaolo Rodolà in

  1836. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8684">bpo-8684</a>.)</p></li>

  1837. <li><p><em>timefunc</em> and <em>delayfunct</em> parameters of <a class="reference internal" href="../library/sched.html#sched.scheduler" title="sched.scheduler"><code class="xref py py-class docutils literal notranslate"><span class="pre">scheduler</span></code></a> class

  1838. constructor are now optional and defaults to <a class="reference internal" href="../library/time.html#time.time" title="time.time"><code class="xref py py-func docutils literal notranslate"><span class="pre">time.time()</span></code></a> and

  1839. <a class="reference internal" href="../library/time.html#time.sleep" title="time.sleep"><code class="xref py py-func docutils literal notranslate"><span class="pre">time.sleep()</span></code></a> respectively.  (Contributed by Chris Clark in

  1840. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13245">bpo-13245</a>.)</p></li>

  1841. <li><p><a class="reference internal" href="../library/sched.html#sched.scheduler.enter" title="sched.scheduler.enter"><code class="xref py py-meth docutils literal notranslate"><span class="pre">enter()</span></code></a> and <a class="reference internal" href="../library/sched.html#sched.scheduler.enterabs" title="sched.scheduler.enterabs"><code class="xref py py-meth docutils literal notranslate"><span class="pre">enterabs()</span></code></a>

  1842. <em>argument</em> parameter is now optional.  (Contributed by Chris Clark in

  1843. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13245">bpo-13245</a>.)</p></li>

  1844. <li><p><a class="reference internal" href="../library/sched.html#sched.scheduler.enter" title="sched.scheduler.enter"><code class="xref py py-meth docutils literal notranslate"><span class="pre">enter()</span></code></a> and <a class="reference internal" href="../library/sched.html#sched.scheduler.enterabs" title="sched.scheduler.enterabs"><code class="xref py py-meth docutils literal notranslate"><span class="pre">enterabs()</span></code></a>

  1845. now accept a <em>kwargs</em> parameter.  (Contributed by Chris Clark in

  1846. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13245">bpo-13245</a>.)</p></li>

  1847. </ul>

  1848. </section>

  1849. <section id="select">

  1850. <h3>select<a class="headerlink" href="#select" title="Link to this heading">¶</a></h3>

  1851. <p>Solaris and derivative platforms have a new class <a class="reference internal" href="../library/select.html#select.devpoll" title="select.devpoll"><code class="xref py py-class docutils literal notranslate"><span class="pre">select.devpoll</span></code></a>

  1852. for high performance asynchronous sockets via <code class="file docutils literal notranslate"><span class="pre">/dev/poll</span></code>.

  1853. (Contributed by Jesús Cea Avión in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6397">bpo-6397</a>.)</p>

  1854. </section>

  1855. <section id="shlex">

  1856. <h3>shlex<a class="headerlink" href="#shlex" title="Link to this heading">¶</a></h3>

  1857. <p>The previously undocumented helper function <code class="docutils literal notranslate"><span class="pre">quote</span></code> from the

  1858. <a class="reference internal" href="../library/pipes.html#module-pipes" title="pipes: A Python interface to Unix shell pipelines. (deprecated) (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">pipes</span></code></a> modules has been moved to the <a class="reference internal" href="../library/shlex.html#module-shlex" title="shlex: Simple lexical analysis for Unix shell-like languages."><code class="xref py py-mod docutils literal notranslate"><span class="pre">shlex</span></code></a> module and

  1859. documented.  <a class="reference internal" href="../library/shlex.html#shlex.quote" title="shlex.quote"><code class="xref py py-func docutils literal notranslate"><span class="pre">quote()</span></code></a> properly escapes all characters in a string

  1860. that might be otherwise given special meaning by the shell.</p>

  1861. </section>

  1862. <section id="shutil">

  1863. <h3>shutil<a class="headerlink" href="#shutil" title="Link to this heading">¶</a></h3>

  1864. <ul class="simple">

  1865. <li><p>New functions:</p>

  1866. <ul>

  1867. <li><p><a class="reference internal" href="../library/shutil.html#shutil.disk_usage" title="shutil.disk_usage"><code class="xref py py-func docutils literal notranslate"><span class="pre">disk_usage()</span></code></a>: provides total, used and free disk space

  1868. statistics.  (Contributed by Giampaolo Rodolà in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12442">bpo-12442</a>.)</p></li>

  1869. <li><p><a class="reference internal" href="../library/shutil.html#shutil.chown" title="shutil.chown"><code class="xref py py-func docutils literal notranslate"><span class="pre">chown()</span></code></a>: allows one to change user and/or group of the given

  1870. path also specifying the user/group names and not only their numeric

  1871. ids.  (Contributed by Sandro Tosi in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12191">bpo-12191</a>.)</p></li>

  1872. <li><p><a class="reference internal" href="../library/shutil.html#shutil.get_terminal_size" title="shutil.get_terminal_size"><code class="xref py py-func docutils literal notranslate"><span class="pre">shutil.get_terminal_size()</span></code></a>: returns the size of the terminal window

  1873. to which the interpreter is attached.  (Contributed by Zbigniew

  1874. Jędrzejewski-Szmek in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13609">bpo-13609</a>.)</p></li>

  1875. </ul>

  1876. </li>

  1877. <li><p><a class="reference internal" href="../library/shutil.html#shutil.copy2" title="shutil.copy2"><code class="xref py py-func docutils literal notranslate"><span class="pre">copy2()</span></code></a> and <a class="reference internal" href="../library/shutil.html#shutil.copystat" title="shutil.copystat"><code class="xref py py-func docutils literal notranslate"><span class="pre">copystat()</span></code></a> now preserve file

  1878. timestamps with nanosecond precision on platforms that support it.

  1879. They also preserve file “extended attributes” on Linux.  (Contributed

  1880. by Larry Hastings in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14127">bpo-14127</a> and  <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=15238">bpo-15238</a>.)</p></li>

  1881. <li><p>Several functions now take an optional <code class="docutils literal notranslate"><span class="pre">symlinks</span></code> argument: when that

  1882. parameter is true, symlinks aren’t dereferenced and the operation instead

  1883. acts on the symlink itself (or creates one, if relevant).

  1884. (Contributed by Hynek Schlawack in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12715">bpo-12715</a>.)</p></li>

  1885. <li><p>When copying files to a different file system, <a class="reference internal" href="../library/shutil.html#shutil.move" title="shutil.move"><code class="xref py py-func docutils literal notranslate"><span class="pre">move()</span></code></a> now

  1886. handles symlinks the way the posix <code class="docutils literal notranslate"><span class="pre">mv</span></code> command does, recreating the

  1887. symlink rather than copying the target file contents.  (Contributed by

  1888. Jonathan Niehof in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=9993">bpo-9993</a>.)  <a class="reference internal" href="../library/shutil.html#shutil.move" title="shutil.move"><code class="xref py py-func docutils literal notranslate"><span class="pre">move()</span></code></a> now also returns

  1889. the <code class="docutils literal notranslate"><span class="pre">dst</span></code> argument as its result.</p></li>

  1890. <li><p><a class="reference internal" href="../library/shutil.html#shutil.rmtree" title="shutil.rmtree"><code class="xref py py-func docutils literal notranslate"><span class="pre">rmtree()</span></code></a> is now resistant to symlink attacks on platforms

  1891. which support the new <code class="docutils literal notranslate"><span class="pre">dir_fd</span></code> parameter in <a class="reference internal" href="../library/os.html#os.open" title="os.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.open()</span></code></a> and

  1892. <a class="reference internal" href="../library/os.html#os.unlink" title="os.unlink"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.unlink()</span></code></a>.  (Contributed by Martin von Löwis and Hynek Schlawack

  1893. in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=4489">bpo-4489</a>.)</p></li>

  1894. </ul>

  1895. </section>

  1896. <section id="signal">

  1897. <h3>signal<a class="headerlink" href="#signal" title="Link to this heading">¶</a></h3>

  1898. <ul class="simple">

  1899. <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 has new functions:</p>

  1900. <ul>

  1901. <li><p><a class="reference internal" href="../library/signal.html#signal.pthread_sigmask" title="signal.pthread_sigmask"><code class="xref py py-func docutils literal notranslate"><span class="pre">pthread_sigmask()</span></code></a>: fetch and/or change the signal mask of the

  1902. calling thread (Contributed by Jean-Paul Calderone in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8407">bpo-8407</a>);</p></li>

  1903. <li><p><a class="reference internal" href="../library/signal.html#signal.pthread_kill" title="signal.pthread_kill"><code class="xref py py-func docutils literal notranslate"><span class="pre">pthread_kill()</span></code></a>: send a signal to a thread;</p></li>

  1904. <li><p><a class="reference internal" href="../library/signal.html#signal.sigpending" title="signal.sigpending"><code class="xref py py-func docutils literal notranslate"><span class="pre">sigpending()</span></code></a>: examine pending functions;</p></li>

  1905. <li><p><a class="reference internal" href="../library/signal.html#signal.sigwait" title="signal.sigwait"><code class="xref py py-func docutils literal notranslate"><span class="pre">sigwait()</span></code></a>: wait a signal;</p></li>

  1906. <li><p><a class="reference internal" href="../library/signal.html#signal.sigwaitinfo" title="signal.sigwaitinfo"><code class="xref py py-func docutils literal notranslate"><span class="pre">sigwaitinfo()</span></code></a>: wait for a signal, returning detailed

  1907. information about it;</p></li>

  1908. <li><p><a class="reference internal" href="../library/signal.html#signal.sigtimedwait" title="signal.sigtimedwait"><code class="xref py py-func docutils literal notranslate"><span class="pre">sigtimedwait()</span></code></a>: like <a class="reference internal" href="../library/signal.html#signal.sigwaitinfo" title="signal.sigwaitinfo"><code class="xref py py-func docutils literal notranslate"><span class="pre">sigwaitinfo()</span></code></a> but with a

  1909. timeout.</p></li>

  1910. </ul>

  1911. </li>

  1912. <li><p>The signal handler writes the signal number as a single byte instead of

  1913. a nul byte into the wakeup file descriptor. So it is possible to wait more

  1914. than one signal and know which signals were raised.</p></li>

  1915. <li><p><a class="reference internal" href="../library/signal.html#signal.signal" title="signal.signal"><code class="xref py py-func docutils literal notranslate"><span class="pre">signal.signal()</span></code></a> and <a class="reference internal" href="../library/signal.html#signal.siginterrupt" title="signal.siginterrupt"><code class="xref py py-func docutils literal notranslate"><span class="pre">signal.siginterrupt()</span></code></a> raise an OSError,

  1916. instead of a RuntimeError: OSError has an errno attribute.</p></li>

  1917. </ul>

  1918. </section>

  1919. <section id="smtpd">

  1920. <h3>smtpd<a class="headerlink" href="#smtpd" title="Link to this heading">¶</a></h3>

  1921. <p>The <code class="xref py py-mod docutils literal notranslate"><span class="pre">smtpd</span></code> module now supports <span class="target" id="index-26"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc5321.html"><strong>RFC 5321</strong></a> (extended SMTP) and <span class="target" id="index-27"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc1870.html"><strong>RFC 1870</strong></a>

  1922. (size extension).  Per the standard, these extensions are enabled if and only

  1923. if the client initiates the session with an <code class="docutils literal notranslate"><span class="pre">EHLO</span></code> command.</p>

  1924. <p>(Initial <code class="docutils literal notranslate"><span class="pre">ELHO</span></code> support by Alberto Trevino.  Size extension by Juhana

  1925. Jauhiainen.  Substantial additional work on the patch contributed by Michele

  1926. Orrù and Dan Boswell.  <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8739">bpo-8739</a>)</p>

  1927. </section>

  1928. <section id="smtplib">

  1929. <h3>smtplib<a class="headerlink" href="#smtplib" title="Link to this heading">¶</a></h3>

  1930. <p>The <a class="reference internal" href="../library/smtplib.html#smtplib.SMTP" title="smtplib.SMTP"><code class="xref py py-class docutils literal notranslate"><span class="pre">SMTP</span></code></a>, <a class="reference internal" href="../library/smtplib.html#smtplib.SMTP_SSL" title="smtplib.SMTP_SSL"><code class="xref py py-class docutils literal notranslate"><span class="pre">SMTP_SSL</span></code></a>, and

  1931. <a class="reference internal" href="../library/smtplib.html#smtplib.LMTP" title="smtplib.LMTP"><code class="xref py py-class docutils literal notranslate"><span class="pre">LMTP</span></code></a> classes now accept a <code class="docutils literal notranslate"><span class="pre">source_address</span></code> keyword argument

  1932. to specify the <code class="docutils literal notranslate"><span class="pre">(host,</span> <span class="pre">port)</span></code> to use as the source address in the bind call

  1933. when creating the outgoing socket.  (Contributed by Paulo Scardine in

  1934. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11281">bpo-11281</a>.)</p>

  1935. <p><a class="reference internal" href="../library/smtplib.html#smtplib.SMTP" title="smtplib.SMTP"><code class="xref py py-class docutils literal notranslate"><span class="pre">SMTP</span></code></a> now supports the context management protocol, allowing an

  1936. <code class="docutils literal notranslate"><span class="pre">SMTP</span></code> instance to be used in a <code class="docutils literal notranslate"><span class="pre">with</span></code> statement.  (Contributed

  1937. by Giampaolo Rodolà in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11289">bpo-11289</a>.)</p>

  1938. <p>The <a class="reference internal" href="../library/smtplib.html#smtplib.SMTP_SSL" title="smtplib.SMTP_SSL"><code class="xref py py-class docutils literal notranslate"><span class="pre">SMTP_SSL</span></code></a> constructor and the <a class="reference internal" href="../library/smtplib.html#smtplib.SMTP.starttls" title="smtplib.SMTP.starttls"><code class="xref py py-meth docutils literal notranslate"><span class="pre">starttls()</span></code></a>

  1939. method now accept an SSLContext parameter to control parameters of the secure

  1940. channel.  (Contributed by Kasun Herath in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8809">bpo-8809</a>.)</p>

  1941. </section>

  1942. <section id="socket">

  1943. <h3>socket<a class="headerlink" href="#socket" title="Link to this heading">¶</a></h3>

  1944. <ul>

  1945. <li><p>The <a class="reference internal" href="../library/socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket</span></code></a> class now exposes additional methods to process

  1946. ancillary data when supported by the underlying platform:</p>

  1947. <ul class="simple">

  1948. <li><p><a class="reference internal" href="../library/socket.html#socket.socket.sendmsg" title="socket.socket.sendmsg"><code class="xref py py-func docutils literal notranslate"><span class="pre">sendmsg()</span></code></a></p></li>

  1949. <li><p><a class="reference internal" href="../library/socket.html#socket.socket.recvmsg" title="socket.socket.recvmsg"><code class="xref py py-func docutils literal notranslate"><span class="pre">recvmsg()</span></code></a></p></li>

  1950. <li><p><a class="reference internal" href="../library/socket.html#socket.socket.recvmsg_into" title="socket.socket.recvmsg_into"><code class="xref py py-func docutils literal notranslate"><span class="pre">recvmsg_into()</span></code></a></p></li>

  1951. </ul>

  1952. <p>(Contributed by David Watson in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6560">bpo-6560</a>, based on an earlier patch by

  1953. Heiko Wundram)</p>

  1954. </li>

  1955. <li><p>The <a class="reference internal" href="../library/socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket</span></code></a> class now supports the PF_CAN protocol family

  1956. (<a class="reference external" href="https://en.wikipedia.org/wiki/Socketcan">https://en.wikipedia.org/wiki/Socketcan</a>), on Linux

  1957. (<a class="reference external" href="https://lwn.net/Articles/253425">https://lwn.net/Articles/253425</a>).</p>

  1958. <p>(Contributed by Matthias Fuchs, updated by Tiago Gonçalves in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10141">bpo-10141</a>.)</p>

  1959. </li>

  1960. <li><p>The <a class="reference internal" href="../library/socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket</span></code></a> class now supports the PF_RDS protocol family

  1961. (<a class="reference external" href="https://en.wikipedia.org/wiki/Reliable_Datagram_Sockets">https://en.wikipedia.org/wiki/Reliable_Datagram_Sockets</a> and

  1962. <a class="reference external" href="https://web.archive.org/web/20130115155505/https://oss.oracle.com/projects/rds/">https://oss.oracle.com/projects/rds</a>).</p></li>

  1963. <li><p>The <a class="reference internal" href="../library/socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket</span></code></a> class now supports the <code class="docutils literal notranslate"><span class="pre">PF_SYSTEM</span></code> protocol

  1964. family on OS X.  (Contributed by Michael Goderbauer in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13777">bpo-13777</a>.)</p></li>

  1965. <li><p>New function <a class="reference internal" href="../library/socket.html#socket.sethostname" title="socket.sethostname"><code class="xref py py-func docutils literal notranslate"><span class="pre">sethostname()</span></code></a> allows the hostname to be set

  1966. on Unix systems if the calling process has sufficient privileges.

  1967. (Contributed by Ross Lagerwall in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10866">bpo-10866</a>.)</p></li>

  1968. </ul>

  1969. </section>

  1970. <section id="socketserver">

  1971. <h3>socketserver<a class="headerlink" href="#socketserver" title="Link to this heading">¶</a></h3>

  1972. <p><a class="reference internal" href="../library/socketserver.html#socketserver.BaseServer" title="socketserver.BaseServer"><code class="xref py py-class docutils literal notranslate"><span class="pre">BaseServer</span></code></a> now has an overridable method

  1973. <a class="reference internal" href="../library/socketserver.html#socketserver.BaseServer.service_actions" title="socketserver.BaseServer.service_actions"><code class="xref py py-meth docutils literal notranslate"><span class="pre">service_actions()</span></code></a> that is called by the

  1974. <a class="reference internal" href="../library/socketserver.html#socketserver.BaseServer.serve_forever" title="socketserver.BaseServer.serve_forever"><code class="xref py py-meth docutils literal notranslate"><span class="pre">serve_forever()</span></code></a> method in the service loop.

  1975. <a class="reference internal" href="../library/socketserver.html#socketserver.ForkingMixIn" title="socketserver.ForkingMixIn"><code class="xref py py-class docutils literal notranslate"><span class="pre">ForkingMixIn</span></code></a> now uses this to clean up zombie

  1976. child processes.  (Contributed by Justin Warkentin in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11109">bpo-11109</a>.)</p>

  1977. </section>

  1978. <section id="sqlite3">

  1979. <h3>sqlite3<a class="headerlink" href="#sqlite3" title="Link to this heading">¶</a></h3>

  1980. <p>New <a class="reference internal" href="../library/sqlite3.html#sqlite3.Connection" title="sqlite3.Connection"><code class="xref py py-class docutils literal notranslate"><span class="pre">sqlite3.Connection</span></code></a> method

  1981. <a class="reference internal" href="../library/sqlite3.html#sqlite3.Connection.set_trace_callback" title="sqlite3.Connection.set_trace_callback"><code class="xref py py-meth docutils literal notranslate"><span class="pre">set_trace_callback()</span></code></a> can be used to capture a trace of

  1982. all sql commands processed by sqlite.  (Contributed by Torsten Landschoff

  1983. in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11688">bpo-11688</a>.)</p>

  1984. </section>

  1985. <section id="ssl">

  1986. <h3>ssl<a class="headerlink" href="#ssl" title="Link to this heading">¶</a></h3>

  1987. <ul>

  1988. <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 has two new random generation functions:</p>

  1989. <ul class="simple">

  1990. <li><p><a class="reference internal" href="../library/ssl.html#ssl.RAND_bytes" title="ssl.RAND_bytes"><code class="xref py py-func docutils literal notranslate"><span class="pre">RAND_bytes()</span></code></a>: generate cryptographically strong

  1991. pseudo-random bytes.</p></li>

  1992. <li><p><code class="xref py py-func docutils literal notranslate"><span class="pre">RAND_pseudo_bytes()</span></code>: generate pseudo-random bytes.</p></li>

  1993. </ul>

  1994. <p>(Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12049">bpo-12049</a>.)</p>

  1995. </li>

  1996. <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 now exposes a finer-grained exception hierarchy

  1997. in order to make it easier to inspect the various kinds of errors.

  1998. (Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11183">bpo-11183</a>.)</p></li>

  1999. <li><p><a class="reference internal" href="../library/ssl.html#ssl.SSLContext.load_cert_chain" title="ssl.SSLContext.load_cert_chain"><code class="xref py py-meth docutils literal notranslate"><span class="pre">load_cert_chain()</span></code></a> now accepts a <em>password</em> argument

  2000. to be used if the private key is encrypted.

  2001. (Contributed by Adam Simpkins in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12803">bpo-12803</a>.)</p></li>

  2002. <li><p>Diffie-Hellman key exchange, both regular and Elliptic Curve-based, is

  2003. now supported through the <a class="reference internal" href="../library/ssl.html#ssl.SSLContext.load_dh_params" title="ssl.SSLContext.load_dh_params"><code class="xref py py-meth docutils literal notranslate"><span class="pre">load_dh_params()</span></code></a> and

  2004. <a class="reference internal" href="../library/ssl.html#ssl.SSLContext.set_ecdh_curve" title="ssl.SSLContext.set_ecdh_curve"><code class="xref py py-meth docutils literal notranslate"><span class="pre">set_ecdh_curve()</span></code></a> methods.

  2005. (Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13626">bpo-13626</a> and <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13627">bpo-13627</a>.)</p></li>

  2006. <li><p>SSL sockets have a new <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket.get_channel_binding" title="ssl.SSLSocket.get_channel_binding"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_channel_binding()</span></code></a> method

  2007. allowing the implementation of certain authentication mechanisms such as

  2008. SCRAM-SHA-1-PLUS.  (Contributed by Jacek Konieczny in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12551">bpo-12551</a>.)</p></li>

  2009. <li><p>You can query the SSL compression algorithm used by an SSL socket, thanks

  2010. to its new <a class="reference internal" href="../library/ssl.html#ssl.SSLSocket.compression" title="ssl.SSLSocket.compression"><code class="xref py py-meth docutils literal notranslate"><span class="pre">compression()</span></code></a> method.  The new attribute

  2011. <a class="reference internal" href="../library/ssl.html#ssl.OP_NO_COMPRESSION" title="ssl.OP_NO_COMPRESSION"><code class="xref py py-const docutils literal notranslate"><span class="pre">OP_NO_COMPRESSION</span></code></a> can be used to disable compression.

  2012. (Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13634">bpo-13634</a>.)</p></li>

  2013. <li><p>Support has been added for the Next Protocol Negotiation extension using

  2014. the <a class="reference internal" href="../library/ssl.html#ssl.SSLContext.set_npn_protocols" title="ssl.SSLContext.set_npn_protocols"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ssl.SSLContext.set_npn_protocols()</span></code></a> method.

  2015. (Contributed by Colin Marc in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14204">bpo-14204</a>.)</p></li>

  2016. <li><p>SSL errors can now be introspected more easily thanks to

  2017. <a class="reference internal" href="../library/ssl.html#ssl.SSLError.library" title="ssl.SSLError.library"><code class="xref py py-attr docutils literal notranslate"><span class="pre">library</span></code></a> and <a class="reference internal" href="../library/ssl.html#ssl.SSLError.reason" title="ssl.SSLError.reason"><code class="xref py py-attr docutils literal notranslate"><span class="pre">reason</span></code></a> attributes.

  2018. (Contributed by Antoine Pitrou in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14837">bpo-14837</a>.)</p></li>

  2019. <li><p>The <a class="reference internal" href="../library/ssl.html#ssl.get_server_certificate" title="ssl.get_server_certificate"><code class="xref py py-func docutils literal notranslate"><span class="pre">get_server_certificate()</span></code></a> function now supports IPv6.

  2020. (Contributed by Charles-François Natali in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11811">bpo-11811</a>.)</p></li>

  2021. <li><p>New attribute <a class="reference internal" href="../library/ssl.html#ssl.OP_CIPHER_SERVER_PREFERENCE" title="ssl.OP_CIPHER_SERVER_PREFERENCE"><code class="xref py py-const docutils literal notranslate"><span class="pre">OP_CIPHER_SERVER_PREFERENCE</span></code></a> allows setting

  2022. SSLv3 server sockets to use the server’s cipher ordering preference rather

  2023. than the client’s (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13635">bpo-13635</a>).</p></li>

  2024. </ul>

  2025. </section>

  2026. <section id="stat">

  2027. <h3>stat<a class="headerlink" href="#stat" title="Link to this heading">¶</a></h3>

  2028. <p>The undocumented tarfile.filemode function has been moved to

  2029. <a class="reference internal" href="../library/stat.html#stat.filemode" title="stat.filemode"><code class="xref py py-func docutils literal notranslate"><span class="pre">stat.filemode()</span></code></a>. It can be used to convert a file’s mode to a string of

  2030. the form ‘-rwxrwxrwx’.</p>

  2031. <p>(Contributed by Giampaolo Rodolà in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14807">bpo-14807</a>.)</p>

  2032. </section>

  2033. <section id="struct">

  2034. <h3>struct<a class="headerlink" href="#struct" title="Link to this heading">¶</a></h3>

  2035. <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 now supports <code class="xref c c-type docutils literal notranslate"><span class="pre">ssize_t</span></code> and <code class="xref c c-type docutils literal notranslate"><span class="pre">size_t</span></code> via the

  2036. new codes <code class="docutils literal notranslate"><span class="pre">n</span></code> and <code class="docutils literal notranslate"><span class="pre">N</span></code>, respectively.  (Contributed by Antoine Pitrou

  2037. in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=3163">bpo-3163</a>.)</p>

  2038. </section>

  2039. <section id="subprocess">

  2040. <h3>subprocess<a class="headerlink" href="#subprocess" title="Link to this heading">¶</a></h3>

  2041. <p>Command strings can now be bytes objects on posix platforms.  (Contributed by

  2042. Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8513">bpo-8513</a>.)</p>

  2043. <p>A new constant <a class="reference internal" href="../library/subprocess.html#subprocess.DEVNULL" title="subprocess.DEVNULL"><code class="xref py py-const docutils literal notranslate"><span class="pre">DEVNULL</span></code></a> allows suppressing output in a

  2044. platform-independent fashion.  (Contributed by Ross Lagerwall in

  2045. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5870">bpo-5870</a>.)</p>

  2046. </section>

  2047. <section id="sys">

  2048. <h3>sys<a class="headerlink" href="#sys" title="Link to this heading">¶</a></h3>

  2049. <p>The <a class="reference internal" href="../library/sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a> module has a new <a class="reference internal" href="../library/sys.html#sys.thread_info" title="sys.thread_info"><code class="xref py py-data docutils literal notranslate"><span class="pre">thread_info</span></code></a> <a class="reference internal" href="../glossary.html#term-named-tuple"><span class="xref std std-term">named

  2050. tuple</span></a> holding information about the thread implementation

  2051. (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11223">bpo-11223</a>).</p>

  2052. </section>

  2053. <section id="tarfile">

  2054. <h3>tarfile<a class="headerlink" href="#tarfile" title="Link to this heading">¶</a></h3>

  2055. <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 <code class="docutils literal notranslate"><span class="pre">lzma</span></code> encoding via the <a class="reference internal" href="../library/lzma.html#module-lzma" title="lzma: A Python wrapper for the liblzma compression library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">lzma</span></code></a> module.

  2056. (Contributed by Lars Gustäbel in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=5689">bpo-5689</a>.)</p>

  2057. </section>

  2058. <section id="tempfile">

  2059. <h3>tempfile<a class="headerlink" href="#tempfile" title="Link to this heading">¶</a></h3>

  2060. <p><a class="reference internal" href="../library/tempfile.html#tempfile.SpooledTemporaryFile" title="tempfile.SpooledTemporaryFile"><code class="xref py py-class docutils literal notranslate"><span class="pre">tempfile.SpooledTemporaryFile</span></code></a>'s

  2061. <code class="xref py py-meth docutils literal notranslate"><span class="pre">truncate()</span></code> method now accepts

  2062. a <code class="docutils literal notranslate"><span class="pre">size</span></code> parameter.  (Contributed by Ryan Kelly in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=9957">bpo-9957</a>.)</p>

  2063. </section>

  2064. <section id="textwrap">

  2065. <h3>textwrap<a class="headerlink" href="#textwrap" title="Link to this heading">¶</a></h3>

  2066. <p>The <a class="reference internal" href="../library/textwrap.html#module-textwrap" title="textwrap: Text wrapping and filling"><code class="xref py py-mod docutils literal notranslate"><span class="pre">textwrap</span></code></a> module has a new <a class="reference internal" href="../library/textwrap.html#textwrap.indent" title="textwrap.indent"><code class="xref py py-func docutils literal notranslate"><span class="pre">indent()</span></code></a> that makes

  2067. it straightforward to add a common prefix to selected lines in a block

  2068. of text  (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13857">bpo-13857</a>).</p>

  2069. </section>

  2070. <section id="threading">

  2071. <h3>threading<a class="headerlink" href="#threading" title="Link to this heading">¶</a></h3>

  2072. <p><a class="reference internal" href="../library/threading.html#threading.Condition" title="threading.Condition"><code class="xref py py-class docutils literal notranslate"><span class="pre">threading.Condition</span></code></a>, <a class="reference internal" href="../library/threading.html#threading.Semaphore" title="threading.Semaphore"><code class="xref py py-class docutils literal notranslate"><span class="pre">threading.Semaphore</span></code></a>,

  2073. <a class="reference internal" href="../library/threading.html#threading.BoundedSemaphore" title="threading.BoundedSemaphore"><code class="xref py py-class docutils literal notranslate"><span class="pre">threading.BoundedSemaphore</span></code></a>, <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>, and

  2074. <a class="reference internal" href="../library/threading.html#threading.Timer" title="threading.Timer"><code class="xref py py-class docutils literal notranslate"><span class="pre">threading.Timer</span></code></a>, all of which used to be factory functions returning a

  2075. class instance, are now classes and may be subclassed.  (Contributed by Éric

  2076. Araujo in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10968">bpo-10968</a>.)</p>

  2077. <p>The <a class="reference internal" href="../library/threading.html#threading.Thread" title="threading.Thread"><code class="xref py py-class docutils literal notranslate"><span class="pre">threading.Thread</span></code></a> constructor now accepts a <code class="docutils literal notranslate"><span class="pre">daemon</span></code> keyword

  2078. argument to override the default behavior of inheriting the <code class="docutils literal notranslate"><span class="pre">daemon</span></code> flag

  2079. value from the parent thread (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=6064">bpo-6064</a>).</p>

  2080. <p>The formerly private function <code class="docutils literal notranslate"><span class="pre">_thread.get_ident</span></code> is now available as the

  2081. public function <a class="reference internal" href="../library/threading.html#threading.get_ident" title="threading.get_ident"><code class="xref py py-func docutils literal notranslate"><span class="pre">threading.get_ident()</span></code></a>.  This eliminates several cases of

  2082. direct access to the <code class="docutils literal notranslate"><span class="pre">_thread</span></code> module in the stdlib.  Third party code that

  2083. used <code class="docutils literal notranslate"><span class="pre">_thread.get_ident</span></code> should likewise be changed to use the new public

  2084. interface.</p>

  2085. </section>

  2086. <section id="time">

  2087. <h3>time<a class="headerlink" href="#time" title="Link to this heading">¶</a></h3>

  2088. <p>The <span class="target" id="index-28"></span><a class="pep reference external" href="https://peps.python.org/pep-0418/"><strong>PEP 418</strong></a> added new functions to the <a class="reference internal" href="../library/time.html#module-time" title="time: Time access and conversions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">time</span></code></a> module:</p>

  2089. <ul class="simple">

  2090. <li><p><a class="reference internal" href="../library/time.html#time.get_clock_info" title="time.get_clock_info"><code class="xref py py-func docutils literal notranslate"><span class="pre">get_clock_info()</span></code></a>: Get information on a clock.</p></li>

  2091. <li><p><a class="reference internal" href="../library/time.html#time.monotonic" title="time.monotonic"><code class="xref py py-func docutils literal notranslate"><span class="pre">monotonic()</span></code></a>: Monotonic clock (cannot go backward), not affected

  2092. by system clock updates.</p></li>

  2093. <li><p><a class="reference internal" href="../library/time.html#time.perf_counter" title="time.perf_counter"><code class="xref py py-func docutils literal notranslate"><span class="pre">perf_counter()</span></code></a>: Performance counter with the highest available

  2094. resolution to measure a short duration.</p></li>

  2095. <li><p><a class="reference internal" href="../library/time.html#time.process_time" title="time.process_time"><code class="xref py py-func docutils literal notranslate"><span class="pre">process_time()</span></code></a>: Sum of the system and user CPU time of the

  2096. current process.</p></li>

  2097. </ul>

  2098. <p>Other new functions:</p>

  2099. <ul class="simple">

  2100. <li><p><a class="reference internal" href="../library/time.html#time.clock_getres" title="time.clock_getres"><code class="xref py py-func docutils literal notranslate"><span class="pre">clock_getres()</span></code></a>, <a class="reference internal" href="../library/time.html#time.clock_gettime" title="time.clock_gettime"><code class="xref py py-func docutils literal notranslate"><span class="pre">clock_gettime()</span></code></a> and

  2101. <a class="reference internal" href="../library/time.html#time.clock_settime" title="time.clock_settime"><code class="xref py py-func docutils literal notranslate"><span class="pre">clock_settime()</span></code></a> functions with <code class="samp docutils literal notranslate"><span class="pre">CLOCK_</span><em><span class="pre">xxx</span></em></code> constants.

  2102. (Contributed by Victor Stinner in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10278">bpo-10278</a>.)</p></li>

  2103. </ul>

  2104. <p>To improve cross platform consistency, <a class="reference internal" href="../library/time.html#time.sleep" title="time.sleep"><code class="xref py py-func docutils literal notranslate"><span class="pre">sleep()</span></code></a> now raises a

  2105. <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> when passed a negative sleep value.  Previously this was an

  2106. error on posix, but produced an infinite sleep on Windows.</p>

  2107. </section>

  2108. <section id="types">

  2109. <h3>types<a class="headerlink" href="#types" title="Link to this heading">¶</a></h3>

  2110. <p>Add a new <a class="reference internal" href="../library/types.html#types.MappingProxyType" title="types.MappingProxyType"><code class="xref py py-class docutils literal notranslate"><span class="pre">types.MappingProxyType</span></code></a> class: Read-only proxy of a mapping.

  2111. (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14386">bpo-14386</a>)</p>

  2112. <p>The new functions <a class="reference internal" href="../library/types.html#types.new_class" title="types.new_class"><code class="xref py py-func docutils literal notranslate"><span class="pre">types.new_class()</span></code></a> and <a class="reference internal" href="../library/types.html#types.prepare_class" title="types.prepare_class"><code class="xref py py-func docutils literal notranslate"><span class="pre">types.prepare_class()</span></code></a> provide support

  2113. for <span class="target" id="index-29"></span><a class="pep reference external" href="https://peps.python.org/pep-3115/"><strong>PEP 3115</strong></a> compliant dynamic type creation. (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14588">bpo-14588</a>)</p>

  2114. </section>

  2115. <section id="unittest">

  2116. <h3>unittest<a class="headerlink" href="#unittest" title="Link to this heading">¶</a></h3>

  2117. <p><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>, <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">assertRaisesRegex()</span></code></a>, <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertWarns" title="unittest.TestCase.assertWarns"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertWarns()</span></code></a>, and

  2118. <a class="reference internal" href="../library/unittest.html#unittest.TestCase.assertWarnsRegex" title="unittest.TestCase.assertWarnsRegex"><code class="xref py py-meth docutils literal notranslate"><span class="pre">assertWarnsRegex()</span></code></a> now accept a keyword argument <em>msg</em> when used as

  2119. context managers.  (Contributed by Ezio Melotti and Winston Ewert in

  2120. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10775">bpo-10775</a>.)</p>

  2121. <p><a class="reference internal" href="../library/unittest.html#unittest.TestCase.run" title="unittest.TestCase.run"><code class="xref py py-meth docutils literal notranslate"><span class="pre">unittest.TestCase.run()</span></code></a> now returns the <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>

  2122. object.</p>

  2123. </section>

  2124. <section id="urllib">

  2125. <h3>urllib<a class="headerlink" href="#urllib" title="Link to this heading">¶</a></h3>

  2126. <p>The <a class="reference internal" href="../library/urllib.request.html#urllib.request.Request" title="urllib.request.Request"><code class="xref py py-class docutils literal notranslate"><span class="pre">Request</span></code></a> class, now accepts a <em>method</em> argument

  2127. used by <a class="reference internal" href="../library/urllib.request.html#urllib.request.Request.get_method" title="urllib.request.Request.get_method"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_method()</span></code></a> to determine what HTTP method

  2128. should be used.  For example, this will send a <code class="docutils literal notranslate"><span class="pre">'HEAD'</span></code> request:</p>

  2129. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">urlopen</span><span class="p">(</span><span class="n">Request</span><span class="p">(</span><span class="s1">&#39;https://www.python.org&#39;</span><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="s1">&#39;HEAD&#39;</span><span class="p">))</span>

  2130. </pre></div>

  2131. </div>

  2132. <p>(<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1673007">bpo-1673007</a>)</p>

  2133. </section>

  2134. <section id="webbrowser">

  2135. <h3>webbrowser<a class="headerlink" href="#webbrowser" title="Link to this heading">¶</a></h3>

  2136. <p>The <a class="reference internal" href="../library/webbrowser.html#module-webbrowser" title="webbrowser: Easy-to-use controller for web browsers."><code class="xref py py-mod docutils literal notranslate"><span class="pre">webbrowser</span></code></a> module supports more “browsers”: Google Chrome (named

  2137. <strong class="program">chrome</strong>, <strong class="program">chromium</strong>, <strong class="program">chrome-browser</strong> or

  2138. <strong class="program">chromium-browser</strong> depending on the version and operating system),

  2139. and the generic launchers <strong class="program">xdg-open</strong>, from the FreeDesktop.org

  2140. project, and <strong class="program">gvfs-open</strong>, which is the default URI handler for GNOME

  2141. 3.  (The former contributed by Arnaud Calmettes in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13620">bpo-13620</a>, the latter

  2142. by Matthias Klose in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14493">bpo-14493</a>.)</p>

  2143. </section>

  2144. <section id="xml-etree-elementtree">

  2145. <h3>xml.etree.ElementTree<a class="headerlink" href="#xml-etree-elementtree" title="Link to this heading">¶</a></h3>

  2146. <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> module now imports its C accelerator by

  2147. default; there is no longer a need to explicitly import

  2148. <code class="xref py py-mod docutils literal notranslate"><span class="pre">xml.etree.cElementTree</span></code> (this module stays for backwards compatibility,

  2149. but is now deprecated).  In addition,  the <code class="docutils literal notranslate"><span class="pre">iter</span></code> family of methods of

  2150. <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> has been optimized (rewritten in C).

  2151. The module’s documentation has also been greatly improved with added examples

  2152. and a more detailed reference.</p>

  2153. </section>

  2154. <section id="zlib">

  2155. <h3>zlib<a class="headerlink" href="#zlib" title="Link to this heading">¶</a></h3>

  2156. <p>New attribute <a class="reference internal" href="../library/zlib.html#zlib.Decompress.eof" title="zlib.Decompress.eof"><code class="xref py py-attr docutils literal notranslate"><span class="pre">zlib.Decompress.eof</span></code></a> makes it possible to distinguish

  2157. between a properly formed compressed stream and an incomplete or truncated one.

  2158. (Contributed by Nadeem Vawda in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12646">bpo-12646</a>.)</p>

  2159. <p>New attribute <a class="reference internal" href="../library/zlib.html#zlib.ZLIB_RUNTIME_VERSION" title="zlib.ZLIB_RUNTIME_VERSION"><code class="xref py py-const docutils literal notranslate"><span class="pre">zlib.ZLIB_RUNTIME_VERSION</span></code></a> reports the version string of

  2160. the underlying <code class="docutils literal notranslate"><span class="pre">zlib</span></code> library that is loaded at runtime.  (Contributed by

  2161. Torsten Landschoff in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12306">bpo-12306</a>.)</p>

  2162. </section>

  2163. </section>

  2164. <section id="optimizations">

  2165. <h2>Optimizations<a class="headerlink" href="#optimizations" title="Link to this heading">¶</a></h2>

  2166. <p>Major performance enhancements have been added:</p>

  2167. <ul>

  2168. <li><p>Thanks to <span class="target" id="index-30"></span><a class="pep reference external" href="https://peps.python.org/pep-0393/"><strong>PEP 393</strong></a>, some operations on Unicode strings have been optimized:</p>

  2169. <ul class="simple">

  2170. <li><p>the memory footprint is divided by 2 to 4 depending on the text</p></li>

  2171. <li><p>encode an ASCII string to UTF-8 doesn’t need to encode characters anymore,

  2172. the UTF-8 representation is shared with the ASCII representation</p></li>

  2173. <li><p>the UTF-8 encoder has been optimized</p></li>

  2174. <li><p>repeating a single ASCII letter and getting a substring of an ASCII string

  2175. is 4 times faster</p></li>

  2176. </ul>

  2177. </li>

  2178. <li><p>UTF-8 is now 2x to 4x faster.  UTF-16 encoding is now up to 10x faster.</p>

  2179. <p>(Contributed by Serhiy Storchaka, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14624">bpo-14624</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14738">bpo-14738</a> and

  2180. <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=15026">bpo-15026</a>.)</p>

  2181. </li>

  2182. </ul>

  2183. </section>

  2184. <section id="build-and-c-api-changes">

  2185. <h2>Build and C API Changes<a class="headerlink" href="#build-and-c-api-changes" title="Link to this heading">¶</a></h2>

  2186. <p>Changes to Python’s build process and to the C API include:</p>

  2187. <ul class="simple">

  2188. <li><p>New <span class="target" id="index-31"></span><a class="pep reference external" href="https://peps.python.org/pep-3118/"><strong>PEP 3118</strong></a> related function:</p>

  2189. <ul>

  2190. <li><p><a class="reference internal" href="../c-api/memoryview.html#c.PyMemoryView_FromMemory" title="PyMemoryView_FromMemory"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMemoryView_FromMemory()</span></code></a></p></li>

  2191. </ul>

  2192. </li>

  2193. <li><p><span class="target" id="index-32"></span><a class="pep reference external" href="https://peps.python.org/pep-0393/"><strong>PEP 393</strong></a> added new Unicode types, macros and functions:</p>

  2194. <ul>

  2195. <li><p>High-level API:</p>

  2196. <ul>

  2197. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_CopyCharacters" title="PyUnicode_CopyCharacters"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_CopyCharacters()</span></code></a></p></li>

  2198. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FindChar" title="PyUnicode_FindChar"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_FindChar()</span></code></a></p></li>

  2199. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_GetLength" title="PyUnicode_GetLength"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_GetLength()</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_GET_LENGTH" title="PyUnicode_GET_LENGTH"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_GET_LENGTH</span></code></a></p></li>

  2200. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_New" title="PyUnicode_New"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_New()</span></code></a></p></li>

  2201. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_Substring" title="PyUnicode_Substring"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_Substring()</span></code></a></p></li>

  2202. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_ReadChar" title="PyUnicode_ReadChar"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_ReadChar()</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_WriteChar" title="PyUnicode_WriteChar"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_WriteChar()</span></code></a></p></li>

  2203. </ul>

  2204. </li>

  2205. <li><p>Low-level API:</p>

  2206. <ul>

  2207. <li><p><a class="reference internal" href="../c-api/unicode.html#c.Py_UCS1" title="Py_UCS1"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_UCS1</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.Py_UCS2" title="Py_UCS2"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_UCS2</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.Py_UCS4" title="Py_UCS4"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_UCS4</span></code></a> types</p></li>

  2208. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyASCIIObject" title="PyASCIIObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyASCIIObject</span></code></a> and <a class="reference internal" href="../c-api/unicode.html#c.PyCompactUnicodeObject" title="PyCompactUnicodeObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyCompactUnicodeObject</span></code></a> structures</p></li>

  2209. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_READY" title="PyUnicode_READY"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_READY</span></code></a></p></li>

  2210. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FromKindAndData" title="PyUnicode_FromKindAndData"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_FromKindAndData()</span></code></a></p></li>

  2211. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsUCS4" title="PyUnicode_AsUCS4"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsUCS4()</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsUCS4Copy" title="PyUnicode_AsUCS4Copy"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsUCS4Copy()</span></code></a></p></li>

  2212. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_DATA" title="PyUnicode_DATA"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_DATA</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_1BYTE_DATA" title="PyUnicode_1BYTE_DATA"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_1BYTE_DATA</span></code></a>,

  2213. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_2BYTE_DATA" title="PyUnicode_2BYTE_DATA"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_2BYTE_DATA</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_4BYTE_DATA" title="PyUnicode_4BYTE_DATA"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_4BYTE_DATA</span></code></a></p></li>

  2214. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_KIND" title="PyUnicode_KIND"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_KIND</span></code></a> with <code class="xref c c-enum docutils literal notranslate"><span class="pre">PyUnicode_Kind</span></code> enum:

  2215. <code class="xref c c-data docutils literal notranslate"><span class="pre">PyUnicode_WCHAR_KIND</span></code>, <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_1BYTE_KIND" title="PyUnicode_1BYTE_KIND"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyUnicode_1BYTE_KIND</span></code></a>,

  2216. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_2BYTE_KIND" title="PyUnicode_2BYTE_KIND"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyUnicode_2BYTE_KIND</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_4BYTE_KIND" title="PyUnicode_4BYTE_KIND"><code class="xref c c-data docutils literal notranslate"><span class="pre">PyUnicode_4BYTE_KIND</span></code></a></p></li>

  2217. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_READ" title="PyUnicode_READ"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_READ</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_READ_CHAR" title="PyUnicode_READ_CHAR"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_READ_CHAR</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_WRITE" title="PyUnicode_WRITE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_WRITE</span></code></a></p></li>

  2218. <li><p><a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_MAX_CHAR_VALUE" title="PyUnicode_MAX_CHAR_VALUE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_MAX_CHAR_VALUE</span></code></a></p></li>

  2219. </ul>

  2220. </li>

  2221. </ul>

  2222. </li>

  2223. <li><p><a class="reference internal" href="../c-api/arg.html#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyArg_ParseTuple</span></code></a> now accepts a <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> for the <code class="docutils literal notranslate"><span class="pre">c</span></code>

  2224. format (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12380">bpo-12380</a>).</p></li>

  2225. </ul>

  2226. </section>

  2227. <section id="deprecated">

  2228. <h2>Deprecated<a class="headerlink" href="#deprecated" title="Link to this heading">¶</a></h2>

  2229. <section id="unsupported-operating-systems">

  2230. <h3>Unsupported Operating Systems<a class="headerlink" href="#unsupported-operating-systems" title="Link to this heading">¶</a></h3>

  2231. <p>OS/2 and VMS are no longer supported due to the lack of a maintainer.</p>

  2232. <p>Windows 2000 and Windows platforms which set <code class="docutils literal notranslate"><span class="pre">COMSPEC</span></code> to <code class="docutils literal notranslate"><span class="pre">command.com</span></code>

  2233. are no longer supported due to maintenance burden.</p>

  2234. <p>OSF support, which was deprecated in 3.2, has been completely removed.</p>

  2235. </section>

  2236. <section id="deprecated-python-modules-functions-and-methods">

  2237. <h3>Deprecated Python modules, functions and methods<a class="headerlink" href="#deprecated-python-modules-functions-and-methods" title="Link to this heading">¶</a></h3>

  2238. <ul class="simple">

  2239. <li><p>Passing a non-empty string to <code class="docutils literal notranslate"><span class="pre">object.__format__()</span></code> is deprecated, and

  2240. will produce 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> in Python 3.4 (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=9856">bpo-9856</a>).</p></li>

  2241. <li><p>The <code class="docutils literal notranslate"><span class="pre">unicode_internal</span></code> codec has been deprecated because of the

  2242. <span class="target" id="index-33"></span><a class="pep reference external" href="https://peps.python.org/pep-0393/"><strong>PEP 393</strong></a>, use UTF-8, UTF-16 (<code class="docutils literal notranslate"><span class="pre">utf-16-le</span></code> or <code class="docutils literal notranslate"><span class="pre">utf-16-be</span></code>), or UTF-32

  2243. (<code class="docutils literal notranslate"><span class="pre">utf-32-le</span></code> or <code class="docutils literal notranslate"><span class="pre">utf-32-be</span></code>)</p></li>

  2244. <li><p><a class="reference internal" href="../library/ftplib.html#ftplib.FTP.nlst" title="ftplib.FTP.nlst"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ftplib.FTP.nlst()</span></code></a> and <a class="reference internal" href="../library/ftplib.html#ftplib.FTP.dir" title="ftplib.FTP.dir"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ftplib.FTP.dir()</span></code></a>: use

  2245. <a class="reference internal" href="../library/ftplib.html#ftplib.FTP.mlsd" title="ftplib.FTP.mlsd"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ftplib.FTP.mlsd()</span></code></a></p></li>

  2246. <li><p><code class="xref py py-func docutils literal notranslate"><span class="pre">platform.popen()</span></code>: use 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. Check especially

  2247. the <a class="reference internal" href="../library/subprocess.html#subprocess-replacements"><span class="std std-ref">Replacing Older Functions with the subprocess Module</span></a> section (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11377">bpo-11377</a>).</p></li>

  2248. <li><p><a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13374">bpo-13374</a>: The Windows bytes API has been deprecated in 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>

  2249. module. Use Unicode filenames, instead of bytes filenames, to not depend on

  2250. the ANSI code page anymore and to support any filename.</p></li>

  2251. <li><p><a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13988">bpo-13988</a>: The <code class="xref py py-mod docutils literal notranslate"><span class="pre">xml.etree.cElementTree</span></code> module is deprecated.  The

  2252. accelerator is used automatically whenever available.</p></li>

  2253. <li><p>The behaviour of <code class="xref py py-func docutils literal notranslate"><span class="pre">time.clock()</span></code> depends on the platform: use the new

  2254. <a class="reference internal" href="../library/time.html#time.perf_counter" title="time.perf_counter"><code class="xref py py-func docutils literal notranslate"><span class="pre">time.perf_counter()</span></code></a> or <a class="reference internal" href="../library/time.html#time.process_time" title="time.process_time"><code class="xref py py-func docutils literal notranslate"><span class="pre">time.process_time()</span></code></a> function instead,

  2255. depending on your requirements, to have a well defined behaviour.</p></li>

  2256. <li><p>The <code class="xref py py-func docutils literal notranslate"><span class="pre">os.stat_float_times()</span></code> function is deprecated.</p></li>

  2257. <li><p><a class="reference internal" href="../library/abc.html#module-abc" title="abc: Abstract base classes according to :pep:`3119`."><code class="xref py py-mod docutils literal notranslate"><span class="pre">abc</span></code></a> module:</p>

  2258. <ul>

  2259. <li><p><a class="reference internal" href="../library/abc.html#abc.abstractproperty" title="abc.abstractproperty"><code class="xref py py-class docutils literal notranslate"><span class="pre">abc.abstractproperty</span></code></a> has been deprecated, use <a class="reference internal" href="../library/functions.html#property" title="property"><code class="xref py py-class docutils literal notranslate"><span class="pre">property</span></code></a>

  2260. with <a class="reference internal" href="../library/abc.html#abc.abstractmethod" title="abc.abstractmethod"><code class="xref py py-func docutils literal notranslate"><span class="pre">abc.abstractmethod()</span></code></a> instead.</p></li>

  2261. <li><p><a class="reference internal" href="../library/abc.html#abc.abstractclassmethod" title="abc.abstractclassmethod"><code class="xref py py-class docutils literal notranslate"><span class="pre">abc.abstractclassmethod</span></code></a> has been deprecated, use

  2262. <a class="reference internal" href="../library/functions.html#classmethod" title="classmethod"><code class="xref py py-class docutils literal notranslate"><span class="pre">classmethod</span></code></a> with <a class="reference internal" href="../library/abc.html#abc.abstractmethod" title="abc.abstractmethod"><code class="xref py py-func docutils literal notranslate"><span class="pre">abc.abstractmethod()</span></code></a> instead.</p></li>

  2263. <li><p><a class="reference internal" href="../library/abc.html#abc.abstractstaticmethod" title="abc.abstractstaticmethod"><code class="xref py py-class docutils literal notranslate"><span class="pre">abc.abstractstaticmethod</span></code></a> has been deprecated, use

  2264. <a class="reference internal" href="../library/functions.html#staticmethod" title="staticmethod"><code class="xref py py-class docutils literal notranslate"><span class="pre">staticmethod</span></code></a> with <a class="reference internal" href="../library/abc.html#abc.abstractmethod" title="abc.abstractmethod"><code class="xref py py-func docutils literal notranslate"><span class="pre">abc.abstractmethod()</span></code></a> instead.</p></li>

  2265. </ul>

  2266. </li>

  2267. <li><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> package:</p>

  2268. <ul>

  2269. <li><p><a class="reference internal" href="../library/importlib.html#importlib.abc.SourceLoader.path_mtime" title="importlib.abc.SourceLoader.path_mtime"><code class="xref py py-meth docutils literal notranslate"><span class="pre">importlib.abc.SourceLoader.path_mtime()</span></code></a> is now deprecated in favour of

  2270. <a class="reference internal" href="../library/importlib.html#importlib.abc.SourceLoader.path_stats" title="importlib.abc.SourceLoader.path_stats"><code class="xref py py-meth docutils literal notranslate"><span class="pre">importlib.abc.SourceLoader.path_stats()</span></code></a> as bytecode files now store

  2271. both the modification time and size of the source file the bytecode file was

  2272. compiled from.</p></li>

  2273. </ul>

  2274. </li>

  2275. </ul>

  2276. </section>

  2277. <section id="deprecated-functions-and-types-of-the-c-api">

  2278. <h3>Deprecated functions and types of the C API<a class="headerlink" href="#deprecated-functions-and-types-of-the-c-api" title="Link to this heading">¶</a></h3>

  2279. <p>The <a class="reference internal" href="../c-api/unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_UNICODE</span></code></a> has been deprecated by <span class="target" id="index-34"></span><a class="pep reference external" href="https://peps.python.org/pep-0393/"><strong>PEP 393</strong></a> and will be

  2280. removed in Python 4. All functions using this type are deprecated:</p>

  2281. <p>Unicode functions and methods using <a class="reference internal" href="../c-api/unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_UNICODE</span></code></a> and

  2282. <span class="c-expr sig sig-inline c"><a class="reference internal" href="../c-api/unicode.html#c.Py_UNICODE" title="Py_UNICODE"><span class="n">Py_UNICODE</span></a><span class="p">*</span></span> types:</p>

  2283. <ul class="simple">

  2284. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_FromUnicode</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FromWideChar" title="PyUnicode_FromWideChar"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_FromWideChar()</span></code></a> or

  2285. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FromKindAndData" title="PyUnicode_FromKindAndData"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_FromKindAndData()</span></code></a></p></li>

  2286. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_AS_UNICODE</span></code>, <code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsUnicode()</span></code>,

  2287. <code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsUnicodeAndSize()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsWideCharString" title="PyUnicode_AsWideCharString"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsWideCharString()</span></code></a></p></li>

  2288. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_AS_DATA</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_DATA" title="PyUnicode_DATA"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_DATA</span></code></a> with

  2289. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_READ" title="PyUnicode_READ"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_READ</span></code></a> and <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_WRITE" title="PyUnicode_WRITE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_WRITE</span></code></a></p></li>

  2290. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_GET_SIZE</span></code>, <code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_GetSize()</span></code>: use

  2291. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_GET_LENGTH" title="PyUnicode_GET_LENGTH"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_GET_LENGTH</span></code></a> or <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_GetLength" title="PyUnicode_GetLength"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_GetLength()</span></code></a></p></li>

  2292. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_GET_DATA_SIZE</span></code>: use

  2293. <code class="docutils literal notranslate"><span class="pre">PyUnicode_GET_LENGTH(str)</span> <span class="pre">*</span> <span class="pre">PyUnicode_KIND(str)</span></code> (only work on ready

  2294. strings)</p></li>

  2295. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsUnicodeCopy()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsUCS4Copy" title="PyUnicode_AsUCS4Copy"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsUCS4Copy()</span></code></a> or

  2296. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsWideCharString" title="PyUnicode_AsWideCharString"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsWideCharString()</span></code></a></p></li>

  2297. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_GetMax()</span></code></p></li>

  2298. </ul>

  2299. <p>Functions and macros manipulating Py_UNICODE* strings:</p>

  2300. <ul class="simple">

  2301. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_strlen()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_GetLength" title="PyUnicode_GetLength"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_GetLength()</span></code></a> or

  2302. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_GET_LENGTH" title="PyUnicode_GET_LENGTH"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyUnicode_GET_LENGTH</span></code></a></p></li>

  2303. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_strcat()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_CopyCharacters" title="PyUnicode_CopyCharacters"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_CopyCharacters()</span></code></a> or

  2304. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FromFormat" title="PyUnicode_FromFormat"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_FromFormat()</span></code></a></p></li>

  2305. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_strcpy()</span></code>, <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_strncpy()</span></code>,

  2306. <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_COPY()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_CopyCharacters" title="PyUnicode_CopyCharacters"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_CopyCharacters()</span></code></a> or

  2307. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_Substring" title="PyUnicode_Substring"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_Substring()</span></code></a></p></li>

  2308. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_strcmp()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_Compare" title="PyUnicode_Compare"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_Compare()</span></code></a></p></li>

  2309. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_strncmp()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_Tailmatch" title="PyUnicode_Tailmatch"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_Tailmatch()</span></code></a></p></li>

  2310. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_strchr()</span></code>, <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_strrchr()</span></code>: use

  2311. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FindChar" title="PyUnicode_FindChar"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_FindChar()</span></code></a></p></li>

  2312. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_FILL()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_Fill" title="PyUnicode_Fill"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_Fill()</span></code></a></p></li>

  2313. <li><p><code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_UNICODE_MATCH</span></code></p></li>

  2314. </ul>

  2315. <p>Encoders:</p>

  2316. <ul class="simple">

  2317. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_Encode()</span></code>: use <code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsEncodedObject()</span></code></p></li>

  2318. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeUTF7()</span></code></p></li>

  2319. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeUTF8()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsUTF8" title="PyUnicode_AsUTF8"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsUTF8()</span></code></a> or

  2320. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsUTF8String" title="PyUnicode_AsUTF8String"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsUTF8String()</span></code></a></p></li>

  2321. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeUTF32()</span></code></p></li>

  2322. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeUTF16()</span></code></p></li>

  2323. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeUnicodeEscape()</span></code> use

  2324. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsUnicodeEscapeString" title="PyUnicode_AsUnicodeEscapeString"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsUnicodeEscapeString()</span></code></a></p></li>

  2325. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeRawUnicodeEscape()</span></code> use

  2326. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsRawUnicodeEscapeString" title="PyUnicode_AsRawUnicodeEscapeString"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsRawUnicodeEscapeString()</span></code></a></p></li>

  2327. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeLatin1()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsLatin1String" title="PyUnicode_AsLatin1String"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsLatin1String()</span></code></a></p></li>

  2328. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeASCII()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsASCIIString" title="PyUnicode_AsASCIIString"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsASCIIString()</span></code></a></p></li>

  2329. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeCharmap()</span></code></p></li>

  2330. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_TranslateCharmap()</span></code></p></li>

  2331. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeMBCS()</span></code>: use <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_AsMBCSString" title="PyUnicode_AsMBCSString"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_AsMBCSString()</span></code></a> or

  2332. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_EncodeCodePage" title="PyUnicode_EncodeCodePage"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeCodePage()</span></code></a> (with <code class="docutils literal notranslate"><span class="pre">CP_ACP</span></code> code_page)</p></li>

  2333. <li><p><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_EncodeDecimal()</span></code>,

  2334. <code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_TransformDecimalToASCII()</span></code></p></li>

  2335. </ul>

  2336. </section>

  2337. <section id="deprecated-features">

  2338. <h3>Deprecated features<a class="headerlink" href="#deprecated-features" title="Link to this heading">¶</a></h3>

  2339. <p>The <a class="reference internal" href="../library/array.html#module-array" title="array: Space efficient arrays of uniformly typed numeric values."><code class="xref py py-mod docutils literal notranslate"><span class="pre">array</span></code></a> module’s <code class="docutils literal notranslate"><span class="pre">'u'</span></code> format code is now deprecated and will be

  2340. removed in Python 4 together with the rest of the (<a class="reference internal" href="../c-api/unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_UNICODE</span></code></a>) API.</p>

  2341. </section>

  2342. </section>

  2343. <section id="porting-to-python-3-3">

  2344. <h2>Porting to Python 3.3<a class="headerlink" href="#porting-to-python-3-3" title="Link to this heading">¶</a></h2>

  2345. <p>This section lists previously described changes and other bugfixes

  2346. that may require changes to your code.</p>

  2347. <section id="porting-python-code">

  2348. <span id="portingpythoncode"></span><h3>Porting Python code<a class="headerlink" href="#porting-python-code" title="Link to this heading">¶</a></h3>

  2349. <ul class="simple">

  2350. <li><p>Hash randomization is enabled by default. Set the <span class="target" id="index-35"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONHASHSEED"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHASHSEED</span></code></a>

  2351. environment variable to <code class="docutils literal notranslate"><span class="pre">0</span></code> to disable hash randomization. See also the

  2352. <a class="reference internal" href="../reference/datamodel.html#object.__hash__" title="object.__hash__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">object.__hash__()</span></code></a> method.</p></li>

  2353. <li><p><a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=12326">bpo-12326</a>: On Linux, sys.platform doesn’t contain the major version

  2354. anymore. It is now always ‘linux’, instead of ‘linux2’ or ‘linux3’ depending

  2355. on the Linux version used to build Python. Replace sys.platform == ‘linux2’

  2356. with sys.platform.startswith(‘linux’), or directly sys.platform == ‘linux’ if

  2357. you don’t need to support older Python versions.</p></li>

  2358. <li><p><a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13847">bpo-13847</a>, <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14180">bpo-14180</a>: <a class="reference internal" href="../library/time.html#module-time" title="time: Time access and conversions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">time</span></code></a> and <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>:

  2359. <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> is now raised instead of <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> if a

  2360. timestamp is out of range. <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> is now raised if C functions

  2361. <code class="xref c c-func docutils literal notranslate"><span class="pre">gmtime()</span></code> or <code class="xref c c-func docutils literal notranslate"><span class="pre">localtime()</span></code> failed.</p></li>

  2362. <li><p>The default finders used by import now utilize a cache of what is contained

  2363. within a specific directory. If you create a Python source file or sourceless

  2364. bytecode file, make sure to call <a class="reference internal" href="../library/importlib.html#importlib.invalidate_caches" title="importlib.invalidate_caches"><code class="xref py py-func docutils literal notranslate"><span class="pre">importlib.invalidate_caches()</span></code></a> to clear

  2365. out the cache for the finders to notice the new file.</p></li>

  2366. <li><p><a class="reference internal" href="../library/exceptions.html#ImportError" title="ImportError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ImportError</span></code></a> now uses the full name of the module that was attempted to

  2367. be imported. Doctests that check ImportErrors’ message will need to be

  2368. updated to use the full name of the module instead of just the tail of the

  2369. name.</p></li>

  2370. <li><p>The <em>index</em> argument to <a class="reference internal" href="../library/functions.html#import__" title="__import__"><code class="xref py py-func docutils literal notranslate"><span class="pre">__import__()</span></code></a> now defaults to 0 instead of -1

  2371. and no longer support negative values. It was an oversight when <span class="target" id="index-36"></span><a class="pep reference external" href="https://peps.python.org/pep-0328/"><strong>PEP 328</strong></a> was

  2372. implemented that the default value remained -1. If you need to continue to

  2373. perform a relative import followed by an absolute import, then perform the

  2374. relative import using an index of 1, followed by another import using an

  2375. index of 0. It is preferred, though, that you use

  2376. <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">importlib.import_module()</span></code></a> rather than call <a class="reference internal" href="../library/functions.html#import__" title="__import__"><code class="xref py py-func docutils literal notranslate"><span class="pre">__import__()</span></code></a> directly.</p></li>

  2377. <li><p><a class="reference internal" href="../library/functions.html#import__" title="__import__"><code class="xref py py-func docutils literal notranslate"><span class="pre">__import__()</span></code></a> no longer allows one to use an index value other than 0

  2378. for top-level modules. E.g. <code class="docutils literal notranslate"><span class="pre">__import__('sys',</span> <span class="pre">level=1)</span></code> is now an error.</p></li>

  2379. <li><p>Because <a class="reference internal" href="../library/sys.html#sys.meta_path" title="sys.meta_path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.meta_path</span></code></a> and <a class="reference internal" href="../library/sys.html#sys.path_hooks" title="sys.path_hooks"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path_hooks</span></code></a> now have finders on

  2380. them by default, you will most likely want to use <code class="xref py py-meth docutils literal notranslate"><span class="pre">list.insert()</span></code> instead

  2381. of <code class="xref py py-meth docutils literal notranslate"><span class="pre">list.append()</span></code> to add to those lists.</p></li>

  2382. <li><p>Because <code class="docutils literal notranslate"><span class="pre">None</span></code> is now inserted into <a class="reference internal" href="../library/sys.html#sys.path_importer_cache" title="sys.path_importer_cache"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path_importer_cache</span></code></a>, if you

  2383. are clearing out entries in the dictionary of paths that do not have a

  2384. finder, you will need to remove keys paired with values of <code class="docutils literal notranslate"><span class="pre">None</span></code> <strong>and</strong>

  2385. <code class="xref py py-class docutils literal notranslate"><span class="pre">imp.NullImporter</span></code> to be backwards-compatible. This will lead to extra

  2386. overhead on older versions of Python that re-insert <code class="docutils literal notranslate"><span class="pre">None</span></code> into

  2387. <a class="reference internal" href="../library/sys.html#sys.path_importer_cache" title="sys.path_importer_cache"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path_importer_cache</span></code></a> where it represents the use of implicit

  2388. finders, but semantically it should not change anything.</p></li>

  2389. <li><p><code class="xref py py-class docutils literal notranslate"><span class="pre">importlib.abc.Finder</span></code> no longer specifies a <code class="docutils literal notranslate"><span class="pre">find_module()</span></code> abstract

  2390. method that must be implemented. If you were relying on subclasses to

  2391. implement that method, make sure to check for the method’s existence first.

  2392. You will probably want to check for <code class="docutils literal notranslate"><span class="pre">find_loader()</span></code> first, though, in the

  2393. case of working with <a class="reference internal" href="../glossary.html#term-path-entry-finder"><span class="xref std std-term">path entry finders</span></a>.</p></li>

  2394. <li><p><a class="reference internal" href="../library/pkgutil.html#module-pkgutil" title="pkgutil: Utilities for the import system."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pkgutil</span></code></a> has been converted to use <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> internally. This

  2395. eliminates many edge cases where the old behaviour of the <span class="target" id="index-37"></span><a class="pep reference external" href="https://peps.python.org/pep-0302/"><strong>PEP 302</strong></a> import

  2396. emulation failed to match the behaviour of the real import system. The

  2397. import emulation itself is still present, but is now deprecated. The

  2398. <a class="reference internal" href="../library/pkgutil.html#pkgutil.iter_importers" title="pkgutil.iter_importers"><code class="xref py py-func docutils literal notranslate"><span class="pre">pkgutil.iter_importers()</span></code></a> and <a class="reference internal" href="../library/pkgutil.html#pkgutil.walk_packages" title="pkgutil.walk_packages"><code class="xref py py-func docutils literal notranslate"><span class="pre">pkgutil.walk_packages()</span></code></a> functions

  2399. special case the standard import hooks so they are still supported even

  2400. though they do not provide the non-standard <code class="docutils literal notranslate"><span class="pre">iter_modules()</span></code> method.</p></li>

  2401. <li><p>A longstanding RFC-compliance bug (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1079">bpo-1079</a>) in the parsing done by

  2402. <a class="reference internal" href="../library/email.header.html#email.header.decode_header" title="email.header.decode_header"><code class="xref py py-func docutils literal notranslate"><span class="pre">email.header.decode_header()</span></code></a> has been fixed.  Code that uses the

  2403. standard idiom to convert encoded headers into unicode

  2404. (<code class="docutils literal notranslate"><span class="pre">str(make_header(decode_header(h))</span></code>) will see no change, but code that

  2405. looks at the individual tuples returned by decode_header will see that

  2406. whitespace that precedes or follows <code class="docutils literal notranslate"><span class="pre">ASCII</span></code> sections is now included in the

  2407. <code class="docutils literal notranslate"><span class="pre">ASCII</span></code> section.  Code that builds headers using <code class="docutils literal notranslate"><span class="pre">make_header</span></code> should

  2408. also continue to work without change, since <code class="docutils literal notranslate"><span class="pre">make_header</span></code> continues to add

  2409. whitespace between <code class="docutils literal notranslate"><span class="pre">ASCII</span></code> and non-<code class="docutils literal notranslate"><span class="pre">ASCII</span></code> sections if it is not already

  2410. present in the input strings.</p></li>

  2411. <li><p><a class="reference internal" href="../library/email.utils.html#email.utils.formataddr" title="email.utils.formataddr"><code class="xref py py-func docutils literal notranslate"><span class="pre">email.utils.formataddr()</span></code></a> now does the correct content transfer

  2412. encoding when passed non-<code class="docutils literal notranslate"><span class="pre">ASCII</span></code> display names.  Any code that depended on

  2413. the previous buggy behavior that preserved the non-<code class="docutils literal notranslate"><span class="pre">ASCII</span></code> unicode in the

  2414. formatted output string will need to be changed (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=1690608">bpo-1690608</a>).</p></li>

  2415. <li><p><a class="reference internal" href="../library/poplib.html#poplib.POP3.quit" title="poplib.POP3.quit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">poplib.POP3.quit()</span></code></a> may now raise protocol errors like all other

  2416. <code class="docutils literal notranslate"><span class="pre">poplib</span></code> methods.  Code that assumes <code class="docutils literal notranslate"><span class="pre">quit</span></code> does not raise

  2417. <a class="reference internal" href="../library/poplib.html#poplib.error_proto" title="poplib.error_proto"><code class="xref py py-exc docutils literal notranslate"><span class="pre">poplib.error_proto</span></code></a> errors may need to be changed if errors on <code class="docutils literal notranslate"><span class="pre">quit</span></code>

  2418. are encountered by a particular application (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11291">bpo-11291</a>).</p></li>

  2419. <li><p>The <code class="docutils literal notranslate"><span class="pre">strict</span></code> argument to <a class="reference internal" href="../library/email.parser.html#email.parser.Parser" title="email.parser.Parser"><code class="xref py py-class docutils literal notranslate"><span class="pre">email.parser.Parser</span></code></a>, deprecated since

  2420. Python 2.4, has finally been removed.</p></li>

  2421. <li><p>The deprecated method <code class="docutils literal notranslate"><span class="pre">unittest.TestCase.assertSameElements</span></code> has been

  2422. removed.</p></li>

  2423. <li><p>The deprecated variable <code class="docutils literal notranslate"><span class="pre">time.accept2dyear</span></code> has been removed.</p></li>

  2424. <li><p>The deprecated <code class="docutils literal notranslate"><span class="pre">Context._clamp</span></code> attribute has been removed from the

  2425. <a class="reference internal" href="../library/decimal.html#module-decimal" title="decimal: Implementation of the General Decimal Arithmetic  Specification."><code class="xref py py-mod docutils literal notranslate"><span class="pre">decimal</span></code></a> module.  It was previously replaced by the public attribute

  2426. <code class="xref py py-attr docutils literal notranslate"><span class="pre">clamp</span></code>.  (See <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=8540">bpo-8540</a>.)</p></li>

  2427. <li><p>The undocumented internal helper class <code class="docutils literal notranslate"><span class="pre">SSLFakeFile</span></code> has been removed

  2428. from <a class="reference internal" href="../library/smtplib.html#module-smtplib" title="smtplib: SMTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">smtplib</span></code></a>, since its functionality has long been provided directly

  2429. by <a class="reference internal" href="../library/socket.html#socket.socket.makefile" title="socket.socket.makefile"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.socket.makefile()</span></code></a>.</p></li>

  2430. <li><p>Passing a negative value to <a class="reference internal" href="../library/time.html#time.sleep" title="time.sleep"><code class="xref py py-func docutils literal notranslate"><span class="pre">time.sleep()</span></code></a> on Windows now raises an

  2431. error instead of sleeping forever.  It has always raised an error on posix.</p></li>

  2432. <li><p>The <code class="docutils literal notranslate"><span class="pre">ast.__version__</span></code> constant has been removed.  If you need to

  2433. make decisions affected by the AST version, use <a class="reference internal" href="../library/sys.html#sys.version_info" title="sys.version_info"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.version_info</span></code></a>

  2434. to make the decision.</p></li>

  2435. <li><p>Code that used to work around the fact that the <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 used

  2436. factory functions by subclassing the private classes will need to change to

  2437. subclass the now-public classes.</p></li>

  2438. <li><p>The undocumented debugging machinery in the threading module has been

  2439. removed, simplifying the code.  This should have no effect on production

  2440. code, but is mentioned here in case any application debug frameworks were

  2441. interacting with it (<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=13550">bpo-13550</a>).</p></li>

  2442. </ul>

  2443. </section>

  2444. <section id="porting-c-code">

  2445. <h3>Porting C code<a class="headerlink" href="#porting-c-code" title="Link to this heading">¶</a></h3>

  2446. <ul>

  2447. <li><p>In the course of changes to the buffer API the undocumented

  2448. <code class="xref c c-member docutils literal notranslate"><span class="pre">smalltable</span></code> member of the

  2449. <a class="reference internal" href="../c-api/buffer.html#c.Py_buffer" title="Py_buffer"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_buffer</span></code></a> structure has been removed and the

  2450. layout of the <code class="xref c c-type docutils literal notranslate"><span class="pre">PyMemoryViewObject</span></code> has changed.</p>

  2451. <p>All extensions relying on the relevant parts in <code class="docutils literal notranslate"><span class="pre">memoryobject.h</span></code>

  2452. or <code class="docutils literal notranslate"><span class="pre">object.h</span></code> must be rebuilt.</p>

  2453. </li>

  2454. <li><p>Due to <a class="reference internal" href="#pep-393"><span class="std std-ref">PEP 393</span></a>, the <a class="reference internal" href="../c-api/unicode.html#c.Py_UNICODE" title="Py_UNICODE"><code class="xref c c-type docutils literal notranslate"><span class="pre">Py_UNICODE</span></code></a> type and all

  2455. functions using this type are deprecated (but will stay available for

  2456. at least five years).  If you were using low-level Unicode APIs to

  2457. construct and access unicode objects and you want to benefit of the

  2458. memory footprint reduction provided by <span class="target" id="index-38"></span><a class="pep reference external" href="https://peps.python.org/pep-0393/"><strong>PEP 393</strong></a>, you have to convert

  2459. your code to the new <a class="reference internal" href="../c-api/unicode.html"><span class="doc">Unicode API</span></a>.</p>

  2460. <p>However, if you only have been using high-level functions such as

  2461. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_Concat" title="PyUnicode_Concat"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_Concat()</span></code></a>, <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_Join" title="PyUnicode_Join"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_Join()</span></code></a> or

  2462. <a class="reference internal" href="../c-api/unicode.html#c.PyUnicode_FromFormat" title="PyUnicode_FromFormat"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyUnicode_FromFormat()</span></code></a>, your code will automatically take

  2463. advantage of the new unicode representations.</p>

  2464. </li>

  2465. <li><p><a class="reference internal" href="../c-api/import.html#c.PyImport_GetMagicNumber" title="PyImport_GetMagicNumber"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyImport_GetMagicNumber()</span></code></a> now returns <code class="docutils literal notranslate"><span class="pre">-1</span></code> upon failure.</p></li>

  2466. <li><p>As a negative value for the <em>level</em> argument to <a class="reference internal" href="../library/functions.html#import__" title="__import__"><code class="xref py py-func docutils literal notranslate"><span class="pre">__import__()</span></code></a> is no

  2467. longer valid, the same now holds for <a class="reference internal" href="../c-api/import.html#c.PyImport_ImportModuleLevel" title="PyImport_ImportModuleLevel"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyImport_ImportModuleLevel()</span></code></a>.

  2468. This also means that the value of <em>level</em> used by

  2469. <a class="reference internal" href="../c-api/import.html#c.PyImport_ImportModuleEx" title="PyImport_ImportModuleEx"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyImport_ImportModuleEx()</span></code></a> is now <code class="docutils literal notranslate"><span class="pre">0</span></code> instead of <code class="docutils literal notranslate"><span class="pre">-1</span></code>.</p></li>

  2470. </ul>

  2471. </section>

  2472. <section id="building-c-extensions">

  2473. <h3>Building C extensions<a class="headerlink" href="#building-c-extensions" title="Link to this heading">¶</a></h3>

  2474. <ul>

  2475. <li><p>The range of possible file names for C extensions has been narrowed.

  2476. Very rarely used spellings have been suppressed: under POSIX, files

  2477. named <code class="docutils literal notranslate"><span class="pre">xxxmodule.so</span></code>, <code class="docutils literal notranslate"><span class="pre">xxxmodule.abi3.so</span></code> and

  2478. <code class="docutils literal notranslate"><span class="pre">xxxmodule.cpython-*.so</span></code> are no longer recognized as implementing

  2479. the <code class="docutils literal notranslate"><span class="pre">xxx</span></code> module.  If you had been generating such files, you have

  2480. to switch to the other spellings (i.e., remove the <code class="docutils literal notranslate"><span class="pre">module</span></code> string

  2481. from the file names).</p>

  2482. <p>(implemented in <a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=14040">bpo-14040</a>.)</p>

  2483. </li>

  2484. </ul>

  2485. </section>

  2486. <section id="command-line-switch-changes">

  2487. <h3>Command Line Switch Changes<a class="headerlink" href="#command-line-switch-changes" title="Link to this heading">¶</a></h3>

  2488. <ul>

  2489. <li><p>The -Q command-line flag and related artifacts have been removed.  Code

  2490. checking sys.flags.division_warning will need updating.</p>

  2491. <p>(<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=10998">bpo-10998</a>, contributed by Éric Araujo.)</p>

  2492. </li>

  2493. <li><p>When <strong class="program">python</strong> is started with <a class="reference internal" href="../using/cmdline.html#cmdoption-S"><code class="xref std std-option docutils literal notranslate"><span class="pre">-S</span></code></a>, <code class="docutils literal notranslate"><span class="pre">import</span> <span class="pre">site</span></code>

  2494. will no longer add site-specific paths to the module search paths.  In

  2495. previous versions, it did.</p>

  2496. <p>(<a class="reference external" href="https://bugs.python.org/issue?&#64;action=redirect&amp;bpo=11591">bpo-11591</a>, contributed by Carl Meyer with editions by Éric Araujo.)</p>

  2497. </li>

  2498. </ul>

  2499. </section>

  2500. </section>

  2501. </section>

  2502. 

  2503. 

  2504.             <div class="clearer"></div>

  2505.           </div>

  2506.         </div>

  2507.       </div>

  2508.       <div class="sphinxsidebar" role="navigation" aria-label="main navigation">

  2509.         <div class="sphinxsidebarwrapper">

  2510.   <div>

  2511.     <h3><a href="../contents.html">Table of Contents</a></h3>

  2512.     <ul>

  2513. <li><a class="reference internal" href="#">What’s New In Python 3.3</a><ul>

  2514. <li><a class="reference internal" href="#summary-release-highlights">Summary – Release highlights</a></li>

  2515. <li><a class="reference internal" href="#pep-405-virtual-environments">PEP 405: Virtual Environments</a></li>

  2516. <li><a class="reference internal" href="#pep-420-implicit-namespace-packages">PEP 420: Implicit Namespace Packages</a></li>

  2517. <li><a class="reference internal" href="#pep-3118-new-memoryview-implementation-and-buffer-protocol-documentation">PEP 3118: New memoryview implementation and buffer protocol documentation</a><ul>

  2518. <li><a class="reference internal" href="#features">Features</a></li>

  2519. <li><a class="reference internal" href="#api-changes">API changes</a></li>

  2520. </ul>

  2521. </li>

  2522. <li><a class="reference internal" href="#pep-393-flexible-string-representation">PEP 393: Flexible String Representation</a><ul>

  2523. <li><a class="reference internal" href="#functionality">Functionality</a></li>

  2524. <li><a class="reference internal" href="#performance-and-resource-usage">Performance and resource usage</a></li>

  2525. </ul>

  2526. </li>

  2527. <li><a class="reference internal" href="#pep-397-python-launcher-for-windows">PEP 397: Python Launcher for Windows</a></li>

  2528. <li><a class="reference internal" href="#pep-3151-reworking-the-os-and-io-exception-hierarchy">PEP 3151: Reworking the OS and IO exception hierarchy</a></li>

  2529. <li><a class="reference internal" href="#pep-380-syntax-for-delegating-to-a-subgenerator">PEP 380: Syntax for Delegating to a Subgenerator</a></li>

  2530. <li><a class="reference internal" href="#pep-409-suppressing-exception-context">PEP 409: Suppressing exception context</a></li>

  2531. <li><a class="reference internal" href="#pep-414-explicit-unicode-literals">PEP 414: Explicit Unicode literals</a></li>

  2532. <li><a class="reference internal" href="#pep-3155-qualified-name-for-classes-and-functions">PEP 3155: Qualified name for classes and functions</a></li>

  2533. <li><a class="reference internal" href="#pep-412-key-sharing-dictionary">PEP 412: Key-Sharing Dictionary</a></li>

  2534. <li><a class="reference internal" href="#pep-362-function-signature-object">PEP 362: Function Signature Object</a></li>

  2535. <li><a class="reference internal" href="#pep-421-adding-sys-implementation">PEP 421: Adding sys.implementation</a><ul>

  2536. <li><a class="reference internal" href="#simplenamespace">SimpleNamespace</a></li>

  2537. </ul>

  2538. </li>

  2539. <li><a class="reference internal" href="#using-importlib-as-the-implementation-of-import">Using importlib as the Implementation of Import</a><ul>

  2540. <li><a class="reference internal" href="#new-apis">New APIs</a></li>

  2541. <li><a class="reference internal" href="#visible-changes">Visible Changes</a></li>

  2542. </ul>

  2543. </li>

  2544. <li><a class="reference internal" href="#other-language-changes">Other Language Changes</a></li>

  2545. <li><a class="reference internal" href="#a-finer-grained-import-lock">A Finer-Grained Import Lock</a></li>

  2546. <li><a class="reference internal" href="#builtin-functions-and-types">Builtin functions and types</a></li>

  2547. <li><a class="reference internal" href="#new-modules">New Modules</a><ul>

  2548. <li><a class="reference internal" href="#faulthandler">faulthandler</a></li>

  2549. <li><a class="reference internal" href="#ipaddress">ipaddress</a></li>

  2550. <li><a class="reference internal" href="#lzma">lzma</a></li>

  2551. </ul>

  2552. </li>

  2553. <li><a class="reference internal" href="#improved-modules">Improved Modules</a><ul>

  2554. <li><a class="reference internal" href="#abc">abc</a></li>

  2555. <li><a class="reference internal" href="#array">array</a></li>

  2556. <li><a class="reference internal" href="#base64">base64</a></li>

  2557. <li><a class="reference internal" href="#binascii">binascii</a></li>

  2558. <li><a class="reference internal" href="#bz2">bz2</a></li>

  2559. <li><a class="reference internal" href="#codecs">codecs</a></li>

  2560. <li><a class="reference internal" href="#collections">collections</a></li>

  2561. <li><a class="reference internal" href="#contextlib">contextlib</a></li>

  2562. <li><a class="reference internal" href="#crypt">crypt</a></li>

  2563. <li><a class="reference internal" href="#curses">curses</a></li>

  2564. <li><a class="reference internal" href="#datetime">datetime</a></li>

  2565. <li><a class="reference internal" href="#decimal">decimal</a><ul>

  2566. <li><a class="reference internal" href="#id1">Features</a></li>

  2567. <li><a class="reference internal" href="#id2">API changes</a></li>

  2568. </ul>

  2569. </li>

  2570. <li><a class="reference internal" href="#email">email</a><ul>

  2571. <li><a class="reference internal" href="#policy-framework">Policy Framework</a></li>

  2572. <li><a class="reference internal" href="#provisional-policy-with-new-header-api">Provisional Policy with New Header API</a></li>

  2573. <li><a class="reference internal" href="#other-api-changes">Other API Changes</a></li>

  2574. </ul>

  2575. </li>

  2576. <li><a class="reference internal" href="#ftplib">ftplib</a></li>

  2577. <li><a class="reference internal" href="#functools">functools</a></li>

  2578. <li><a class="reference internal" href="#gc">gc</a></li>

  2579. <li><a class="reference internal" href="#hmac">hmac</a></li>

  2580. <li><a class="reference internal" href="#http">http</a></li>

  2581. <li><a class="reference internal" href="#html">html</a></li>

  2582. <li><a class="reference internal" href="#imaplib">imaplib</a></li>

  2583. <li><a class="reference internal" href="#inspect">inspect</a></li>

  2584. <li><a class="reference internal" href="#io">io</a></li>

  2585. <li><a class="reference internal" href="#itertools">itertools</a></li>

  2586. <li><a class="reference internal" href="#logging">logging</a></li>

  2587. <li><a class="reference internal" href="#math">math</a></li>

  2588. <li><a class="reference internal" href="#mmap">mmap</a></li>

  2589. <li><a class="reference internal" href="#multiprocessing">multiprocessing</a></li>

  2590. <li><a class="reference internal" href="#nntplib">nntplib</a></li>

  2591. <li><a class="reference internal" href="#os">os</a></li>

  2592. <li><a class="reference internal" href="#pdb">pdb</a></li>

  2593. <li><a class="reference internal" href="#pickle">pickle</a></li>

  2594. <li><a class="reference internal" href="#pydoc">pydoc</a></li>

  2595. <li><a class="reference internal" href="#re">re</a></li>

  2596. <li><a class="reference internal" href="#sched">sched</a></li>

  2597. <li><a class="reference internal" href="#select">select</a></li>

  2598. <li><a class="reference internal" href="#shlex">shlex</a></li>

  2599. <li><a class="reference internal" href="#shutil">shutil</a></li>

  2600. <li><a class="reference internal" href="#signal">signal</a></li>

  2601. <li><a class="reference internal" href="#smtpd">smtpd</a></li>

  2602. <li><a class="reference internal" href="#smtplib">smtplib</a></li>

  2603. <li><a class="reference internal" href="#socket">socket</a></li>

  2604. <li><a class="reference internal" href="#socketserver">socketserver</a></li>

  2605. <li><a class="reference internal" href="#sqlite3">sqlite3</a></li>

  2606. <li><a class="reference internal" href="#ssl">ssl</a></li>

  2607. <li><a class="reference internal" href="#stat">stat</a></li>

  2608. <li><a class="reference internal" href="#struct">struct</a></li>

  2609. <li><a class="reference internal" href="#subprocess">subprocess</a></li>

  2610. <li><a class="reference internal" href="#sys">sys</a></li>

  2611. <li><a class="reference internal" href="#tarfile">tarfile</a></li>

  2612. <li><a class="reference internal" href="#tempfile">tempfile</a></li>

  2613. <li><a class="reference internal" href="#textwrap">textwrap</a></li>

  2614. <li><a class="reference internal" href="#threading">threading</a></li>

  2615. <li><a class="reference internal" href="#time">time</a></li>

  2616. <li><a class="reference internal" href="#types">types</a></li>

  2617. <li><a class="reference internal" href="#unittest">unittest</a></li>

  2618. <li><a class="reference internal" href="#urllib">urllib</a></li>

  2619. <li><a class="reference internal" href="#webbrowser">webbrowser</a></li>

  2620. <li><a class="reference internal" href="#xml-etree-elementtree">xml.etree.ElementTree</a></li>

  2621. <li><a class="reference internal" href="#zlib">zlib</a></li>

  2622. </ul>

  2623. </li>

  2624. <li><a class="reference internal" href="#optimizations">Optimizations</a></li>

  2625. <li><a class="reference internal" href="#build-and-c-api-changes">Build and C API Changes</a></li>

  2626. <li><a class="reference internal" href="#deprecated">Deprecated</a><ul>

  2627. <li><a class="reference internal" href="#unsupported-operating-systems">Unsupported Operating Systems</a></li>

  2628. <li><a class="reference internal" href="#deprecated-python-modules-functions-and-methods">Deprecated Python modules, functions and methods</a></li>

  2629. <li><a class="reference internal" href="#deprecated-functions-and-types-of-the-c-api">Deprecated functions and types of the C API</a></li>

  2630. <li><a class="reference internal" href="#deprecated-features">Deprecated features</a></li>

  2631. </ul>

  2632. </li>

  2633. <li><a class="reference internal" href="#porting-to-python-3-3">Porting to Python 3.3</a><ul>

  2634. <li><a class="reference internal" href="#porting-python-code">Porting Python code</a></li>

  2635. <li><a class="reference internal" href="#porting-c-code">Porting C code</a></li>

  2636. <li><a class="reference internal" href="#building-c-extensions">Building C extensions</a></li>

  2637. <li><a class="reference internal" href="#command-line-switch-changes">Command Line Switch Changes</a></li>

  2638. </ul>

  2639. </li>

  2640. </ul>

  2641. </li>

  2642. </ul>

  2643. 

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  2647.     <p class="topless"><a href="3.4.html"

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