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  193.   <section id="module-shelve">

  194. <span id="shelve-python-object-persistence"></span><h1><a class="reference internal" href="#module-shelve" title="shelve: Python object persistence."><code class="xref py py-mod docutils literal notranslate"><span class="pre">shelve</span></code></a> — Python object persistence<a class="headerlink" href="#module-shelve" title="Link to this heading">¶</a></h1>

  195. <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.12/Lib/shelve.py">Lib/shelve.py</a></p>

  196. <hr class="docutils" id="index-0" />

  197. <p>A “shelf” is a persistent, dictionary-like object.  The difference with “dbm”

  198. databases is that the values (not the keys!) in a shelf can be essentially

  199. arbitrary Python objects — anything that the <a class="reference internal" href="pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code></a> module can handle.

  200. This includes most class instances, recursive data types, and objects containing

  201. lots of shared  sub-objects.  The keys are ordinary strings.</p>

  202. <dl class="py function">

  203. <dt class="sig sig-object py" id="shelve.open">

  204. <span class="sig-prename descclassname"><span class="pre">shelve.</span></span><span class="sig-name descname"><span class="pre">open</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">filename</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">flag</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">'c'</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">protocol</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">writeback</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#shelve.open" title="Link to this definition">¶</a></dt>

  205. <dd><p>Open a persistent dictionary.  The filename specified is the base filename for

  206. the underlying database.  As a side-effect, an extension may be added to the

  207. filename and more than one file may be created.  By default, the underlying

  208. database file is opened for reading and writing.  The optional <em>flag</em> parameter

  209. has the same interpretation as the <em>flag</em> parameter of <a class="reference internal" href="dbm.html#dbm.open" title="dbm.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">dbm.open()</span></code></a>.</p>

  210. <p>By default, pickles created with <a class="reference internal" href="pickle.html#pickle.DEFAULT_PROTOCOL" title="pickle.DEFAULT_PROTOCOL"><code class="xref py py-const docutils literal notranslate"><span class="pre">pickle.DEFAULT_PROTOCOL</span></code></a> are used

  211. to serialize values.  The version of the pickle protocol can be specified

  212. with the <em>protocol</em> parameter.</p>

  213. <p>Because of Python semantics, a shelf cannot know when a mutable

  214. persistent-dictionary entry is modified.  By default modified objects are

  215. written <em>only</em> when assigned to the shelf (see <a class="reference internal" href="#shelve-example"><span class="std std-ref">Example</span></a>).  If the

  216. optional <em>writeback</em> parameter is set to <code class="docutils literal notranslate"><span class="pre">True</span></code>, all entries accessed are also

  217. cached in memory, and written back on <a class="reference internal" href="#shelve.Shelf.sync" title="shelve.Shelf.sync"><code class="xref py py-meth docutils literal notranslate"><span class="pre">sync()</span></code></a> and

  218. <a class="reference internal" href="#shelve.Shelf.close" title="shelve.Shelf.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a>; this can make it handier to mutate mutable entries in

  219. the persistent dictionary, but, if many entries are accessed, it can consume

  220. vast amounts of memory for the cache, and it can make the close operation

  221. very slow since all accessed entries are written back (there is no way to

  222. determine which accessed entries are mutable, nor which ones were actually

  223. mutated).</p>

  224. <div class="versionchanged">

  225. <p><span class="versionmodified changed">Changed in version 3.10: </span><a class="reference internal" href="pickle.html#pickle.DEFAULT_PROTOCOL" title="pickle.DEFAULT_PROTOCOL"><code class="xref py py-const docutils literal notranslate"><span class="pre">pickle.DEFAULT_PROTOCOL</span></code></a> is now used as the default pickle

  226. protocol.</p>

  227. </div>

  228. <div class="versionchanged">

  229. <p><span class="versionmodified changed">Changed in version 3.11: </span>Accepts <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">path-like object</span></a> for filename.</p>

  230. </div>

  231. <div class="admonition note">

  232. <p class="admonition-title">Note</p>

  233. <p>Do not rely on the shelf being closed automatically; always call

  234. <a class="reference internal" href="#shelve.Shelf.close" title="shelve.Shelf.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a> explicitly when you don’t need it any more, or

  235. use <a class="reference internal" href="#shelve.open" title="shelve.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">shelve.open()</span></code></a> as a context manager:</p>

  236. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">with</span> <span class="n">shelve</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="s1">&#39;spam&#39;</span><span class="p">)</span> <span class="k">as</span> <span class="n">db</span><span class="p">:</span>

  237.     <span class="n">db</span><span class="p">[</span><span class="s1">&#39;eggs&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s1">&#39;eggs&#39;</span>

  238. </pre></div>

  239. </div>

  240. </div>

  241. </dd></dl>

  242. 

  243. <div class="admonition warning" id="shelve-security">

  244. <p class="admonition-title">Warning</p>

  245. <p>Because the <a class="reference internal" href="#module-shelve" title="shelve: Python object persistence."><code class="xref py py-mod docutils literal notranslate"><span class="pre">shelve</span></code></a> module is backed by <a class="reference internal" href="pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code></a>, it is insecure

  246. to load a shelf from an untrusted source.  Like with pickle, loading a shelf

  247. can execute arbitrary code.</p>

  248. </div>

  249. <p>Shelf objects support most of methods and operations supported by dictionaries

  250. (except copying, constructors and operators <code class="docutils literal notranslate"><span class="pre">|</span></code> and <code class="docutils literal notranslate"><span class="pre">|=</span></code>).  This eases the

  251. transition from dictionary based scripts to those requiring persistent storage.</p>

  252. <p>Two additional methods are supported:</p>

  253. <dl class="py method">

  254. <dt class="sig sig-object py" id="shelve.Shelf.sync">

  255. <span class="sig-prename descclassname"><span class="pre">Shelf.</span></span><span class="sig-name descname"><span class="pre">sync</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#shelve.Shelf.sync" title="Link to this definition">¶</a></dt>

  256. <dd><p>Write back all entries in the cache if the shelf was opened with <em>writeback</em>

  257. set to <a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal notranslate"><span class="pre">True</span></code></a>.  Also empty the cache and synchronize the persistent

  258. dictionary on disk, if feasible.  This is called automatically when the shelf

  259. is closed with <a class="reference internal" href="#shelve.Shelf.close" title="shelve.Shelf.close"><code class="xref py py-meth docutils literal notranslate"><span class="pre">close()</span></code></a>.</p>

  260. </dd></dl>

  261. 

  262. <dl class="py method">

  263. <dt class="sig sig-object py" id="shelve.Shelf.close">

  264. <span class="sig-prename descclassname"><span class="pre">Shelf.</span></span><span class="sig-name descname"><span class="pre">close</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#shelve.Shelf.close" title="Link to this definition">¶</a></dt>

  265. <dd><p>Synchronize and close the persistent <em>dict</em> object.  Operations on a closed

  266. shelf will fail with a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a>.</p>

  267. </dd></dl>

  268. 

  269. <div class="admonition seealso">

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

  271. <p><a class="reference external" href="https://code.activestate.com/recipes/576642/">Persistent dictionary recipe</a>

  272. with widely supported storage formats and having the speed of native

  273. dictionaries.</p>

  274. </div>

  275. <section id="restrictions">

  276. <h2>Restrictions<a class="headerlink" href="#restrictions" title="Link to this heading">¶</a></h2>

  277. <ul class="simple" id="index-1">

  278. <li><p>The choice of which database package will be used (such as <a class="reference internal" href="dbm.html#module-dbm.ndbm" title="dbm.ndbm: The New Database Manager (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm.ndbm</span></code></a> or

  279. <a class="reference internal" href="dbm.html#module-dbm.gnu" title="dbm.gnu: GNU database manager (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm.gnu</span></code></a>) depends on which interface is available.  Therefore it is not

  280. safe to open the database directly using <a class="reference internal" href="dbm.html#module-dbm" title="dbm: Interfaces to various Unix &quot;database&quot; formats."><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm</span></code></a>.  The database is also

  281. (unfortunately) subject to the limitations of <a class="reference internal" href="dbm.html#module-dbm" title="dbm: Interfaces to various Unix &quot;database&quot; formats."><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm</span></code></a>, if it is used —

  282. this means that (the pickled representation of) the objects stored in the

  283. database should be fairly small, and in rare cases key collisions may cause

  284. the database to refuse updates.</p></li>

  285. <li><p>The <a class="reference internal" href="#module-shelve" title="shelve: Python object persistence."><code class="xref py py-mod docutils literal notranslate"><span class="pre">shelve</span></code></a> module does not support <em>concurrent</em> read/write access to

  286. shelved objects.  (Multiple simultaneous read accesses are safe.)  When a

  287. program has a shelf open for writing, no other program should have it open for

  288. reading or writing.  Unix file locking can be used to solve this, but this

  289. differs across Unix versions and requires knowledge about the database

  290. implementation used.</p></li>

  291. <li><p>On macOS <a class="reference internal" href="dbm.html#module-dbm.ndbm" title="dbm.ndbm: The New Database Manager (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm.ndbm</span></code></a> can silently corrupt the database file on updates,

  292. which can cause hard crashes when trying to read from the database.</p></li>

  293. </ul>

  294. <dl class="py class">

  295. <dt class="sig sig-object py" id="shelve.Shelf">

  296. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">shelve.</span></span><span class="sig-name descname"><span class="pre">Shelf</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">dict</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">protocol</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">writeback</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">keyencoding</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">'utf-8'</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#shelve.Shelf" title="Link to this definition">¶</a></dt>

  297. <dd><p>A subclass of <a class="reference internal" href="collections.abc.html#collections.abc.MutableMapping" title="collections.abc.MutableMapping"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.abc.MutableMapping</span></code></a> which stores pickled

  298. values in the <em>dict</em> object.</p>

  299. <p>By default, pickles created with <a class="reference internal" href="pickle.html#pickle.DEFAULT_PROTOCOL" title="pickle.DEFAULT_PROTOCOL"><code class="xref py py-const docutils literal notranslate"><span class="pre">pickle.DEFAULT_PROTOCOL</span></code></a> are used

  300. to serialize values.  The version of the pickle protocol can be specified

  301. with the <em>protocol</em> parameter.  See the <a class="reference internal" href="pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code></a> documentation for a

  302. discussion of the pickle protocols.</p>

  303. <p>If the <em>writeback</em> parameter is <code class="docutils literal notranslate"><span class="pre">True</span></code>, the object will hold a cache of all

  304. entries accessed and write them back to the <em>dict</em> at sync and close times.

  305. This allows natural operations on mutable entries, but can consume much more

  306. memory and make sync and close take a long time.</p>

  307. <p>The <em>keyencoding</em> parameter is the encoding used to encode keys before they

  308. are used with the underlying dict.</p>

  309. <p>A <a class="reference internal" href="#shelve.Shelf" title="shelve.Shelf"><code class="xref py py-class docutils literal notranslate"><span class="pre">Shelf</span></code></a> object can also be used as a context manager, in which

  310. case it will be automatically closed when the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> block ends.</p>

  311. <div class="versionchanged">

  312. <p><span class="versionmodified changed">Changed in version 3.2: </span>Added the <em>keyencoding</em> parameter; previously, keys were always encoded in

  313. UTF-8.</p>

  314. </div>

  315. <div class="versionchanged">

  316. <p><span class="versionmodified changed">Changed in version 3.4: </span>Added context manager support.</p>

  317. </div>

  318. <div class="versionchanged">

  319. <p><span class="versionmodified changed">Changed in version 3.10: </span><a class="reference internal" href="pickle.html#pickle.DEFAULT_PROTOCOL" title="pickle.DEFAULT_PROTOCOL"><code class="xref py py-const docutils literal notranslate"><span class="pre">pickle.DEFAULT_PROTOCOL</span></code></a> is now used as the default pickle

  320. protocol.</p>

  321. </div>

  322. </dd></dl>

  323. 

  324. <dl class="py class">

  325. <dt class="sig sig-object py" id="shelve.BsdDbShelf">

  326. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">shelve.</span></span><span class="sig-name descname"><span class="pre">BsdDbShelf</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">dict</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">protocol</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">writeback</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">keyencoding</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">'utf-8'</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#shelve.BsdDbShelf" title="Link to this definition">¶</a></dt>

  327. <dd><p>A subclass of <a class="reference internal" href="#shelve.Shelf" title="shelve.Shelf"><code class="xref py py-class docutils literal notranslate"><span class="pre">Shelf</span></code></a> which exposes <code class="xref py py-meth docutils literal notranslate"><span class="pre">first()</span></code>, <code class="xref py py-meth docutils literal notranslate"><span class="pre">next()</span></code>,

  328. <code class="xref py py-meth docutils literal notranslate"><span class="pre">previous()</span></code>, <code class="xref py py-meth docutils literal notranslate"><span class="pre">last()</span></code> and <code class="xref py py-meth docutils literal notranslate"><span class="pre">set_location()</span></code> methods.

  329. These are available

  330. in the third-party <code class="xref py py-mod docutils literal notranslate"><span class="pre">bsddb</span></code> module from <a class="reference external" href="https://www.jcea.es/programacion/pybsddb.htm">pybsddb</a> but not in other database

  331. modules.  The <em>dict</em> object passed to the constructor must support those

  332. methods.  This is generally accomplished by calling one of

  333. <code class="xref py py-func docutils literal notranslate"><span class="pre">bsddb.hashopen()</span></code>, <code class="xref py py-func docutils literal notranslate"><span class="pre">bsddb.btopen()</span></code> or <code class="xref py py-func docutils literal notranslate"><span class="pre">bsddb.rnopen()</span></code>.  The

  334. optional <em>protocol</em>, <em>writeback</em>, and <em>keyencoding</em> parameters have the same

  335. interpretation as for the <a class="reference internal" href="#shelve.Shelf" title="shelve.Shelf"><code class="xref py py-class docutils literal notranslate"><span class="pre">Shelf</span></code></a> class.</p>

  336. </dd></dl>

  337. 

  338. <dl class="py class">

  339. <dt class="sig sig-object py" id="shelve.DbfilenameShelf">

  340. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">shelve.</span></span><span class="sig-name descname"><span class="pre">DbfilenameShelf</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">filename</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">flag</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">'c'</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">protocol</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">writeback</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#shelve.DbfilenameShelf" title="Link to this definition">¶</a></dt>

  341. <dd><p>A subclass of <a class="reference internal" href="#shelve.Shelf" title="shelve.Shelf"><code class="xref py py-class docutils literal notranslate"><span class="pre">Shelf</span></code></a> which accepts a <em>filename</em> instead of a dict-like

  342. object.  The underlying file will be opened using <a class="reference internal" href="dbm.html#dbm.open" title="dbm.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">dbm.open()</span></code></a>.  By

  343. default, the file will be created and opened for both read and write.  The

  344. optional <em>flag</em> parameter has the same interpretation as for the <a class="reference internal" href="#shelve.open" title="shelve.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">open()</span></code></a>

  345. function.  The optional <em>protocol</em> and <em>writeback</em> parameters have the same

  346. interpretation as for the <a class="reference internal" href="#shelve.Shelf" title="shelve.Shelf"><code class="xref py py-class docutils literal notranslate"><span class="pre">Shelf</span></code></a> class.</p>

  347. </dd></dl>

  348. 

  349. </section>

  350. <section id="example">

  351. <span id="shelve-example"></span><h2>Example<a class="headerlink" href="#example" title="Link to this heading">¶</a></h2>

  352. <p>To summarize the interface (<code class="docutils literal notranslate"><span class="pre">key</span></code> is a string, <code class="docutils literal notranslate"><span class="pre">data</span></code> is an arbitrary

  353. object):</p>

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

  355. 

  356. <span class="n">d</span> <span class="o">=</span> <span class="n">shelve</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="n">filename</span><span class="p">)</span>  <span class="c1"># open -- file may get suffix added by low-level</span>

  357.                            <span class="c1"># library</span>

  358. 

  359. <span class="n">d</span><span class="p">[</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="n">data</span>              <span class="c1"># store data at key (overwrites old data if</span>

  360.                            <span class="c1"># using an existing key)</span>

  361. <span class="n">data</span> <span class="o">=</span> <span class="n">d</span><span class="p">[</span><span class="n">key</span><span class="p">]</span>              <span class="c1"># retrieve a COPY of data at key (raise KeyError</span>

  362.                            <span class="c1"># if no such key)</span>

  363. <span class="k">del</span> <span class="n">d</span><span class="p">[</span><span class="n">key</span><span class="p">]</span>                 <span class="c1"># delete data stored at key (raises KeyError</span>

  364.                            <span class="c1"># if no such key)</span>

  365. 

  366. <span class="n">flag</span> <span class="o">=</span> <span class="n">key</span> <span class="ow">in</span> <span class="n">d</span>            <span class="c1"># true if the key exists</span>

  367. <span class="n">klist</span> <span class="o">=</span> <span class="nb">list</span><span class="p">(</span><span class="n">d</span><span class="o">.</span><span class="n">keys</span><span class="p">())</span>     <span class="c1"># a list of all existing keys (slow!)</span>

  368. 

  369. <span class="c1"># as d was opened WITHOUT writeback=True, beware:</span>

  370. <span class="n">d</span><span class="p">[</span><span class="s1">&#39;xx&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="p">[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">]</span>        <span class="c1"># this works as expected, but...</span>

  371. <span class="n">d</span><span class="p">[</span><span class="s1">&#39;xx&#39;</span><span class="p">]</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>          <span class="c1"># *this doesn&#39;t!* -- d[&#39;xx&#39;] is STILL [0, 1, 2]!</span>

  372. 

  373. <span class="c1"># having opened d without writeback=True, you need to code carefully:</span>

  374. <span class="n">temp</span> <span class="o">=</span> <span class="n">d</span><span class="p">[</span><span class="s1">&#39;xx&#39;</span><span class="p">]</span>             <span class="c1"># extracts the copy</span>

  375. <span class="n">temp</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span>             <span class="c1"># mutates the copy</span>

  376. <span class="n">d</span><span class="p">[</span><span class="s1">&#39;xx&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="n">temp</span>             <span class="c1"># stores the copy right back, to persist it</span>

  377. 

  378. <span class="c1"># or, d=shelve.open(filename,writeback=True) would let you just code</span>

  379. <span class="c1"># d[&#39;xx&#39;].append(5) and have it work as expected, BUT it would also</span>

  380. <span class="c1"># consume more memory and make the d.close() operation slower.</span>

  381. 

  382. <span class="n">d</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>                  <span class="c1"># close it</span>

  383. </pre></div>

  384. </div>

  385. <div class="admonition seealso">

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

  387. <dl class="simple">

  388. <dt>Module <a class="reference internal" href="dbm.html#module-dbm" title="dbm: Interfaces to various Unix &quot;database&quot; formats."><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm</span></code></a></dt><dd><p>Generic interface to <code class="docutils literal notranslate"><span class="pre">dbm</span></code>-style databases.</p>

  389. </dd>

  390. <dt>Module <a class="reference internal" href="pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code></a></dt><dd><p>Object serialization used by <a class="reference internal" href="#module-shelve" title="shelve: Python object persistence."><code class="xref py py-mod docutils literal notranslate"><span class="pre">shelve</span></code></a>.</p>

  391. </dd>

  392. </dl>

  393. </div>

  394. </section>

  395. </section>

  396. 

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  406.     <ul>

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