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<div class="section" id="module-copyreg">
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<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>
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<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>
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<hr class="docutils" id="index-0" />
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<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
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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
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when pickling/copying those objects. The module provides configuration
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information about object constructors which are not classes.
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Such constructors may be factory functions or class instances.</p>
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<dl class="function">
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<dt id="copyreg.constructor">
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<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>
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<dd><p>Declares <em>object</em> to be a valid constructor. If <em>object</em> is not callable (and
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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>
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</dd></dl>
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<dl class="function">
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<dt id="copyreg.pickle">
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<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>
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<dd><p>Declares that <em>function</em> should be used as a “reduction” function for objects
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of type <em>type</em>. <em>function</em> should return either a string or a tuple
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containing two or three elements.</p>
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<p>The optional <em>constructor</em> parameter, if provided, is a callable object which
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can be used to reconstruct the object when called with the tuple of arguments
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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
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<em>object</em> is a class or <em>constructor</em> is not callable.</p>
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<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
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expected of <em>function</em> and <em>constructor</em>. Note that the
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<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
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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
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declaring reduction functions.</p>
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</dd></dl>
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<div class="section" id="example">
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<h2>Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h2>
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<p>The example below would like to show how to register a pickle function and how
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it will be used:</p>
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<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>
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<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>
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<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>
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<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>
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<span class="gp">...</span>
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<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>
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<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>
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<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>
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<span class="gp">...</span>
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<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>
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<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>
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<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>
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<span class="go">pickling a C instance...</span>
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<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>
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<span class="go">pickling a C instance...</span>
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</pre></div>
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<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>
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<li><a class="reference internal" href="#example">Example</a></li>
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title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code> — Python object serialization</a></p>
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title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">shelve</span></code> — Python object persistence</a></p>
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