<!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8" /> <title>copyreg — Register pickle support functions — Python 3.7.4 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 3.7.4 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="shelve — Python object persistence" href="shelve.html" /> <link rel="prev" title="pickle — Python object serialization" href="pickle.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="https://docs.python.org/3/library/copyreg.html" /> <script type="text/javascript" src="../_static/copybutton.js"></script> <script type="text/javascript" src="../_static/switchers.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="shelve.html" title="shelve — Python object persistence" accesskey="N">next</a> |</li> <li class="right" > <a href="pickle.html" title="pickle — Python object serialization" 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> <span class="language_switcher_placeholder">en</span> <span class="version_switcher_placeholder">3.7.4</span> <a href="../index.html">Documentation </a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="persistence.html" accesskey="U">Data Persistence</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="module-copyreg"> <span id="copyreg-register-pickle-support-functions"></span><h1><a class="reference internal" href="#module-copyreg" title="copyreg: Register pickle support functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">copyreg</span></code></a> — Register <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> support functions<a class="headerlink" href="#module-copyreg" title="Permalink to this headline">¶</a></h1> <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.7/Lib/copyreg.py">Lib/copyreg.py</a></p> <hr class="docutils" id="index-0" /> <p>The <a class="reference internal" href="#module-copyreg" title="copyreg: Register pickle support functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">copyreg</span></code></a> module offers a way to define functions used while pickling specific objects. 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="copy.html#module-copy" title="copy: Shallow and deep copy operations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">copy</span></code></a> modules use those functions when pickling/copying those objects. The module provides configuration information about object constructors which are not classes. Such constructors may be factory functions or class instances.</p> <dl class="function"> <dt id="copyreg.constructor"> <code class="descclassname">copyreg.</code><code class="descname">constructor</code><span class="sig-paren">(</span><em>object</em><span class="sig-paren">)</span><a class="headerlink" href="#copyreg.constructor" title="Permalink to this definition">¶</a></dt> <dd><p>Declares <em>object</em> to be a valid constructor. If <em>object</em> is not callable (and hence not valid as a constructor), raises <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>.</p> </dd></dl> <dl class="function"> <dt id="copyreg.pickle"> <code class="descclassname">copyreg.</code><code class="descname">pickle</code><span class="sig-paren">(</span><em>type</em>, <em>function</em>, <em>constructor=None</em><span class="sig-paren">)</span><a class="headerlink" href="#copyreg.pickle" title="Permalink to this definition">¶</a></dt> <dd><p>Declares that <em>function</em> should be used as a “reduction” function for objects of type <em>type</em>. <em>function</em> should return either a string or a tuple containing two or three elements.</p> <p>The optional <em>constructor</em> parameter, if provided, is a callable object which can be used to reconstruct the object when called with the tuple of arguments returned by <em>function</em> at pickling time. <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> will be raised if <em>object</em> is a class or <em>constructor</em> is not callable.</p> <p>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> module for more details on the interface expected of <em>function</em> and <em>constructor</em>. Note that the <a class="reference internal" href="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 of a pickler object or subclass of <a class="reference internal" href="pickle.html#pickle.Pickler" title="pickle.Pickler"><code class="xref py py-class docutils literal notranslate"><span class="pre">pickle.Pickler</span></code></a> can also be used for declaring reduction functions.</p> </dd></dl> <div class="section" id="example"> <h2>Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h2> <p>The example below would like to show how to register a pickle function and how it will be used:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">copyreg</span><span class="o">,</span> <span class="nn">copy</span><span class="o">,</span> <span class="nn">pickle</span> <span class="gp">>>> </span><span class="k">class</span> <span class="nc">C</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span> <span class="gp">... </span> <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">a</span><span class="p">):</span> <span class="gp">... </span> <span class="bp">self</span><span class="o">.</span><span class="n">a</span> <span class="o">=</span> <span class="n">a</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="k">def</span> <span class="nf">pickle_c</span><span class="p">(</span><span class="n">c</span><span class="p">):</span> <span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="s2">"pickling a C instance..."</span><span class="p">)</span> <span class="gp">... </span> <span class="k">return</span> <span class="n">C</span><span class="p">,</span> <span class="p">(</span><span class="n">c</span><span class="o">.</span><span class="n">a</span><span class="p">,)</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="n">copyreg</span><span class="o">.</span><span class="n">pickle</span><span class="p">(</span><span class="n">C</span><span class="p">,</span> <span class="n">pickle_c</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="n">C</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">d</span> <span class="o">=</span> <span class="n">copy</span><span class="o">.</span><span class="n">copy</span><span class="p">(</span><span class="n">c</span><span class="p">)</span> <span class="c1"># doctest: +SKIP</span> <span class="go">pickling a C instance...</span> <span class="gp">>>> </span><span class="n">p</span> <span class="o">=</span> <span class="n">pickle</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="n">c</span><span class="p">)</span> <span class="c1"># doctest: +SKIP</span> <span class="go">pickling a C instance...</span> </pre></div> </div> </div> </div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <div class="sphinxsidebarwrapper"> <h3><a href="../contents.html">Table of Contents</a></h3> <ul> <li><a class="reference internal" href="#"><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><a class="reference internal" href="#example">Example</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="pickle.html" title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code> — Python object serialization</a></p> <h4>Next topic</h4> <p class="topless"><a href="shelve.html" title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">shelve</span></code> — Python object persistence</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> <li> <a href="https://github.com/python/cpython/blob/3.7/Doc/library/copyreg.rst" rel="nofollow">Show Source </a> </li> </ul> </div> </div> </div> <div class="clearer"></div> </div> <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" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="shelve.html" title="shelve — Python object persistence" >next</a> |</li> <li class="right" > <a href="pickle.html" title="pickle — Python object serialization" >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> <span class="language_switcher_placeholder">en</span> <span class="version_switcher_placeholder">3.7.4</span> <a href="../index.html">Documentation </a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="persistence.html" >Data Persistence</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="footer"> © <a href="../copyright.html">Copyright</a> 2001-2019, Python Software Foundation. <br /> The Python Software Foundation is a non-profit corporation. <a href="https://www.python.org/psf/donations/">Please donate.</a> <br /> Last updated on Jul 13, 2019. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 2.0.1. </div> </body> </html>