Edit File: persistence.html
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>11. Data Persistence — Python 2.7.5 documentation</title> <link rel="stylesheet" href="../_static/default.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../', VERSION: '2.7.5', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </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/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.5 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="top" title="Python 2.7.5 documentation" href="../index.html" /> <link rel="up" title="The Python Standard Library" href="index.html" /> <link rel="next" title="11.1. pickle — Python object serialization" href="pickle.html" /> <link rel="prev" title="10.12. macpath — Mac OS 9 path manipulation functions" href="macpath.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head> <body> <div class="related"> <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="11.1. pickle — Python object serialization" accesskey="N">next</a> |</li> <li class="right" > <a href="macpath.html" title="10.12. 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="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" accesskey="U">The Python Standard Library</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="data-persistence"> <span id="persistence"></span><h1>11. 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."><tt class="xref py py-mod docutils literal"><span class="pre">pickle</span></tt></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)."><tt class="xref py py-mod docutils literal"><span class="pre">marshal</span></tt></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. The <a class="reference internal" href="bsddb.html#module-bsddb" title="bsddb: Interface to Berkeley DB database library"><tt class="xref py py-mod docutils literal"><span class="pre">bsddb</span></tt></a> module also provides such disk-based string-to-string mappings based on hashing, and also supports B-Tree and record-based formats.</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">11.1. <tt class="docutils literal"><span class="pre">pickle</span></tt> — Python object serialization</a><ul> <li class="toctree-l2"><a class="reference internal" href="pickle.html#relationship-to-other-python-modules">11.1.1. Relationship to other Python modules</a></li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#data-stream-format">11.1.2. Data stream format</a></li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#usage">11.1.3. Usage</a></li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#what-can-be-pickled-and-unpickled">11.1.4. What can be pickled and unpickled?</a></li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#the-pickle-protocol">11.1.5. The pickle protocol</a><ul> <li class="toctree-l3"><a class="reference internal" href="pickle.html#pickling-and-unpickling-normal-class-instances">11.1.5.1. Pickling and unpickling normal class instances</a></li> <li class="toctree-l3"><a class="reference internal" href="pickle.html#pickling-and-unpickling-extension-types">11.1.5.2. Pickling and unpickling extension types</a></li> <li class="toctree-l3"><a class="reference internal" href="pickle.html#pickling-and-unpickling-external-objects">11.1.5.3. Pickling and unpickling external objects</a></li> </ul> </li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#subclassing-unpicklers">11.1.6. Subclassing Unpicklers</a></li> <li class="toctree-l2"><a class="reference internal" href="pickle.html#example">11.1.7. Example</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="pickle.html#module-cPickle">11.2. <tt class="docutils literal"><span class="pre">cPickle</span></tt> — A faster <tt class="docutils literal"><span class="pre">pickle</span></tt></a></li> <li class="toctree-l1"><a class="reference internal" href="copy_reg.html">11.3. <tt class="docutils literal"><span class="pre">copy_reg</span></tt> — Register <tt class="docutils literal"><span class="pre">pickle</span></tt> support functions</a><ul> <li class="toctree-l2"><a class="reference internal" href="copy_reg.html#example">11.3.1. Example</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="shelve.html">11.4. <tt class="docutils literal"><span class="pre">shelve</span></tt> — Python object persistence</a><ul> <li class="toctree-l2"><a class="reference internal" href="shelve.html#restrictions">11.4.1. Restrictions</a></li> <li class="toctree-l2"><a class="reference internal" href="shelve.html#example">11.4.2. Example</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="marshal.html">11.5. <tt class="docutils literal"><span class="pre">marshal</span></tt> — Internal Python object serialization</a></li> <li class="toctree-l1"><a class="reference internal" href="anydbm.html">11.6. <tt class="docutils literal"><span class="pre">anydbm</span></tt> — Generic access to DBM-style databases</a></li> <li class="toctree-l1"><a class="reference internal" href="whichdb.html">11.7. <tt class="docutils literal"><span class="pre">whichdb</span></tt> — Guess which DBM module created a database</a></li> <li class="toctree-l1"><a class="reference internal" href="dbm.html">11.8. <tt class="docutils literal"><span class="pre">dbm</span></tt> — Simple “database” interface</a></li> <li class="toctree-l1"><a class="reference internal" href="gdbm.html">11.9. <tt class="docutils literal"><span class="pre">gdbm</span></tt> — GNU’s reinterpretation of dbm</a></li> <li class="toctree-l1"><a class="reference internal" href="dbhash.html">11.10. <tt class="docutils literal"><span class="pre">dbhash</span></tt> — DBM-style interface to the BSD database library</a><ul> <li class="toctree-l2"><a class="reference internal" href="dbhash.html#database-objects">11.10.1. Database Objects</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="bsddb.html">11.11. <tt class="docutils literal"><span class="pre">bsddb</span></tt> — Interface to Berkeley DB library</a><ul> <li class="toctree-l2"><a class="reference internal" href="bsddb.html#hash-btree-and-record-objects">11.11.1. Hash, BTree and Record Objects</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="dumbdbm.html">11.12. <tt class="docutils literal"><span class="pre">dumbdbm</span></tt> — Portable DBM implementation</a><ul> <li class="toctree-l2"><a class="reference internal" href="dumbdbm.html#dumbdbm-objects">11.12.1. Dumbdbm Objects</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="sqlite3.html">11.13. <tt class="docutils literal"><span class="pre">sqlite3</span></tt> — 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">11.13.1. Module functions and constants</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#connection-objects">11.13.2. Connection Objects</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#cursor-objects">11.13.3. Cursor Objects</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#row-objects">11.13.4. Row Objects</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#sqlite-and-python-types">11.13.5. SQLite and Python types</a><ul> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#introduction">11.13.5.1. Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#using-adapters-to-store-additional-python-types-in-sqlite-databases">11.13.5.2. 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">11.13.5.2.1. Letting your object adapt itself</a></li> <li class="toctree-l4"><a class="reference internal" href="sqlite3.html#registering-an-adapter-callable">11.13.5.2.2. 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">11.13.5.3. Converting SQLite values to custom Python types</a></li> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#default-adapters-and-converters">11.13.5.4. Default adapters and converters</a></li> </ul> </li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#controlling-transactions">11.13.6. Controlling Transactions</a></li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#using-sqlite3-efficiently">11.13.7. Using <tt class="docutils literal"><span class="pre">sqlite3</span></tt> efficiently</a><ul> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#using-shortcut-methods">11.13.7.1. Using shortcut methods</a></li> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#accessing-columns-by-name-instead-of-by-index">11.13.7.2. 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">11.13.7.3. Using the connection as a context manager</a></li> </ul> </li> <li class="toctree-l2"><a class="reference internal" href="sqlite3.html#common-issues">11.13.8. Common issues</a><ul> <li class="toctree-l3"><a class="reference internal" href="sqlite3.html#multithreading">11.13.8.1. Multithreading</a></li> </ul> </li> </ul> </li> </ul> </div> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="macpath.html" title="previous chapter">10.12. <tt class="docutils literal"><span class="pre">macpath</span></tt> — Mac OS 9 path manipulation functions</a></p> <h4>Next topic</h4> <p class="topless"><a href="pickle.html" title="next chapter">11.1. <tt class="docutils literal"><span class="pre">pickle</span></tt> — Python object serialization</a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li><a href="../_sources/library/persistence.txt" rel="nofollow">Show Source</a></li> </ul> <div id="searchbox" style="display: none"> <h3>Quick search</h3> <form class="search" action="../search.html" method="get"> <input 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> <p class="searchtip" style="font-size: 90%"> Enter search terms or a module, class or function name. </p> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >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="11.1. pickle — Python object serialization" >next</a> |</li> <li class="right" > <a href="macpath.html" title="10.12. macpath — Mac OS 9 path manipulation functions" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >The Python Standard Library</a> »</li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 1990-2020, Python Software Foundation. <br /> The Python Software Foundation is a non-profit corporation. <a href="http://www.python.org/psf/donations/">Please donate.</a> <br /> Last updated on Oct 13, 2020. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3. </div> </body> </html>