<!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8" /> <title>Data Persistence — Python 3.7.10 documentation</title> <link rel="stylesheet" href="../_static/pydoctheme.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript" id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/language_data.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 3.7.10 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="index" title="Index" href="../genindex.html" /> <link rel="search" title="Search" href="../search.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="next" title="pickle — Python object serialization" href="pickle.html" /> <link rel="prev" title="macpath — Mac OS 9 path manipulation functions" href="macpath.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="https://docs.python.org/3/library/persistence.html" /> <script type="text/javascript" src="../_static/copybutton.js"></script> <style> @media only screen { table.full-width-table { width: 100%; } } </style> </head><body> <div class="related" role="navigation" aria-label="related navigation"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="pickle.html" title="pickle — Python object serialization" accesskey="N">next</a> |</li> <li class="right" > <a href="macpath.html" title="macpath — Mac OS 9 path manipulation functions" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">3.7.10 Documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" accesskey="U">The Python Standard Library</a> »</li> <li class="right"> <div class="inline-search" style="display: none" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> <script type="text/javascript">$('.inline-search').show(0);</script> | </li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <div class="section" id="data-persistence"> <span id="persistence"></span><h1>Data Persistence<a class="headerlink" href="#data-persistence" title="Permalink to this headline">¶</a></h1> <p>The modules described in this chapter support storing Python data in a persistent form on disk. 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> and <a class="reference internal" href="marshal.html#module-marshal" title="marshal: Convert Python objects to streams of bytes and back (with different constraints)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">marshal</span></code></a> modules can turn many Python data types into a stream of bytes and then recreate the objects from the bytes. The various DBM-related modules support a family of hash-based file formats that store a mapping of strings to other strings.</p> <p>The list of modules described in this chapter is:</p> <div class="toctree-wrapper compound"> <ul> <li class="toctree-l1"><a class="reference internal" href="pickle.html"><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code> — Python object serialization</a><ul> <li class="toctree-l2"><a class="reference internal" href="pickle.html#relationship-to-other-python-modules">Relationship to other Python modules</a><ul> <li class="toctree-l3"><a class="reference internal" href="pickle.html#comparison-with-marshal">Comparison with <code class="docutils literal notranslate"><span class="pre">marshal</span></code></a></li> <li class="toctree-l3"><a class="reference internal" href="pickle.html#comparison-with-json">Comparison with <code class="docutils literal notranslate"><span class="pre">json</span></code></a></li> </ul> </li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#data-stream-format">Data stream format</a></li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#module-interface">Module Interface</a></li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#what-can-be-pickled-and-unpickled">What can be pickled and unpickled?</a></li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#pickling-class-instances">Pickling Class Instances</a><ul> <li class="toctree-l3"><a class="reference internal" href="pickle.html#persistence-of-external-objects">Persistence of External Objects</a></li> <li class="toctree-l3"><a class="reference internal" href="pickle.html#dispatch-tables">Dispatch Tables</a></li> <li class="toctree-l3"><a class="reference internal" href="pickle.html#handling-stateful-objects">Handling Stateful Objects</a></li> </ul> </li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#restricting-globals">Restricting Globals</a></li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#performance">Performance</a></li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#examples">Examples</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="copyreg.html"><code class="xref py py-mod docutils literal notranslate"><span class="pre">copyreg</span></code> — Register <code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code> support functions</a><ul> <li class="toctree-l2"><a class="reference internal" href="copyreg.html#example">Example</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="shelve.html"><code class="xref py py-mod docutils literal notranslate"><span class="pre">shelve</span></code> — Python object persistence</a><ul> <li class="toctree-l2"><a class="reference internal" href="shelve.html#restrictions">Restrictions</a></li> <li class="toctree-l2"><a class="reference internal" href="shelve.html#example">Example</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="marshal.html"><code class="xref py py-mod docutils literal notranslate"><span class="pre">marshal</span></code> — Internal Python object serialization</a></li> <li class="toctree-l1"><a class="reference internal" href="dbm.html"><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm</span></code> — Interfaces to Unix “databases”</a><ul> <li class="toctree-l2"><a class="reference internal" href="dbm.html#module-dbm.gnu"><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm.gnu</span></code> — GNU’s reinterpretation of dbm</a></li> <li class="toctree-l2"><a class="reference internal" href="dbm.html#module-dbm.ndbm"><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm.ndbm</span></code> — Interface based on ndbm</a></li> <li class="toctree-l2"><a class="reference internal" href="dbm.html#module-dbm.dumb"><code class="xref py py-mod docutils literal notranslate"><span class="pre">dbm.dumb</span></code> — Portable DBM implementation</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="sqlite3.html"><code class="xref py py-mod docutils literal notranslate"><span class="pre">sqlite3</span></code> — DB-API 2.0 interface for SQLite databases</a><ul> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#module-functions-and-constants">Module functions and constants</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#connection-objects">Connection Objects</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#cursor-objects">Cursor Objects</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#row-objects">Row Objects</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#exceptions">Exceptions</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#sqlite-and-python-types">SQLite and Python types</a><ul> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#introduction">Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#using-adapters-to-store-additional-python-types-in-sqlite-databases">Using adapters to store additional Python types in SQLite databases</a><ul> <li class="toctree-l4"><a class="reference internal" href="sqlite3.html#letting-your-object-adapt-itself">Letting your object adapt itself</a></li> <li class="toctree-l4"><a class="reference internal" href="sqlite3.html#registering-an-adapter-callable">Registering an adapter callable</a></li> </ul> </li> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#converting-sqlite-values-to-custom-python-types">Converting SQLite values to custom Python types</a></li> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#default-adapters-and-converters">Default adapters and converters</a></li> </ul> </li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#controlling-transactions">Controlling Transactions</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#using-sqlite3-efficiently">Using <code class="xref py py-mod docutils literal notranslate"><span class="pre">sqlite3</span></code> efficiently</a><ul> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#using-shortcut-methods">Using shortcut methods</a></li> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#accessing-columns-by-name-instead-of-by-index">Accessing columns by name instead of by index</a></li> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#using-the-connection-as-a-context-manager">Using the connection as a context manager</a></li> </ul> </li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#common-issues">Common issues</a><ul> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#multithreading">Multithreading</a></li> </ul> </li> </ul> </li> </ul> </div> </div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="macpath.html" title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">macpath</span></code> — Mac OS 9 path manipulation functions</a></p> <h4>Next topic</h4> <p class="topless"><a href="pickle.html" title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code> — Python object serialization</a></p> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> 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