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<section id="cell-objects">
<span id="id1"></span><h1>Cell Objects<a class="headerlink" href="#cell-objects" title="Link to this heading">¶</a></h1>
<p>“Cell” objects are used to implement variables referenced by multiple scopes.
For each such variable, a cell object is created to store the value; the local
variables of each stack frame that references the value contains a reference to
the cells from outer scopes which also use that variable. When the value is
accessed, the value contained in the cell is used instead of the cell object
itself. This de-referencing of the cell object requires support from the
generated byte-code; these are not automatically de-referenced when accessed.
Cell objects are not likely to be useful elsewhere.</p>
<dl class="c type">
<dt class="sig sig-object c" id="c.PyCellObject">
<span class="k"><span class="pre">type</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyCellObject</span></span></span><a class="headerlink" href="#c.PyCellObject" title="Link to this definition">¶</a><br /></dt>
<dd><p>The C structure used for cell objects.</p>
</dd></dl>
<dl class="c var">
<dt class="sig sig-object c" id="c.PyCell_Type">
<a class="reference internal" href="type.html#c.PyTypeObject" title="PyTypeObject"><span class="n"><span class="pre">PyTypeObject</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyCell_Type</span></span></span><a class="headerlink" href="#c.PyCell_Type" title="Link to this definition">¶</a><br /></dt>
<dd><p>The type object corresponding to cell objects.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyCell_Check">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyCell_Check</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">ob</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyCell_Check" title="Link to this definition">¶</a><br /></dt>
<dd><p>Return true if <em>ob</em> is a cell object; <em>ob</em> must not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>. This
function always succeeds.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyCell_New">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyCell_New</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">ob</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyCell_New" title="Link to this definition">¶</a><br /></dt>
<dd><em class="refcount return_new_ref">Return value: New reference.</em><p>Create and return a new cell object containing the value <em>ob</em>. The parameter may
be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyCell_Get">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyCell_Get</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">cell</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyCell_Get" title="Link to this definition">¶</a><br /></dt>
<dd><em class="refcount return_new_ref">Return value: New reference.</em><p>Return the contents of the cell <em>cell</em>.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyCell_GET">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyCell_GET</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">cell</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyCell_GET" title="Link to this definition">¶</a><br /></dt>
<dd><em class="refcount return_borrowed_ref">Return value: Borrowed reference.</em><p>Return the contents of the cell <em>cell</em>, but without checking that <em>cell</em> is
non-<code class="docutils literal notranslate"><span class="pre">NULL</span></code> and a cell object.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyCell_Set">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyCell_Set</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">cell</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">value</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyCell_Set" title="Link to this definition">¶</a><br /></dt>
<dd><p>Set the contents of the cell object <em>cell</em> to <em>value</em>. This releases the
reference to any current content of the cell. <em>value</em> may be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>. <em>cell</em>
must be non-<code class="docutils literal notranslate"><span class="pre">NULL</span></code>; if it is not a cell object, <code class="docutils literal notranslate"><span class="pre">-1</span></code> will be returned. On
success, <code class="docutils literal notranslate"><span class="pre">0</span></code> will be returned.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyCell_SET">
<span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyCell_SET</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">cell</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">value</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyCell_SET" title="Link to this definition">¶</a><br /></dt>
<dd><p>Sets the value of the cell object <em>cell</em> to <em>value</em>. No reference counts are
adjusted, and no checks are made for safety; <em>cell</em> must be non-<code class="docutils literal notranslate"><span class="pre">NULL</span></code> and must
be a cell object.</p>
</dd></dl>
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