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| 55 | <H2><A NAME="SECTION0095100000000000000000"></A><A NAME="cell-objects"></A> |
| 56 | <BR> |
| 57 | 7.5.10 Cell Objects |
| 58 | </H2> |
| 59 | |
| 60 | <P> |
| 61 | ``Cell'' objects are used to implement variables referenced by |
| 62 | multiple scopes. For each such variable, a cell object is created to |
| 63 | store the value; the local variables of each stack frame that |
| 64 | references the value contains a reference to the cells from outer |
| 65 | scopes which also use that variable. When the value is accessed, the |
| 66 | value contained in the cell is used instead of the cell object |
| 67 | itself. This de-referencing of the cell object requires support from |
| 68 | the generated byte-code; these are not automatically de-referenced |
| 69 | when accessed. Cell objects are not likely to be useful elsewhere. |
| 70 | |
| 71 | <P> |
| 72 | <dl><dt><b><tt class="ctype"><a id='l2h-733' xml:id='l2h-733'>PyCellObject</a></tt></b></dt> |
| 73 | <dd> |
| 74 | The C structure used for cell objects. |
| 75 | </dl> |
| 76 | |
| 77 | <P> |
| 78 | <dl><dt>PyTypeObject <b><tt id='l2h-734' xml:id='l2h-734' class="cdata">PyCell_Type</tt></b></dt> |
| 79 | <dd> |
| 80 | The type object corresponding to cell objects |
| 81 | </dd></dl> |
| 82 | |
| 83 | <P> |
| 84 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-735' xml:id='l2h-735' class="cfunction">PyCell_Check</tt></b>(</nobr></td><td>ob)</td></tr></table></dt> |
| 85 | <dd> |
| 86 | Return true if <var>ob</var> is a cell object; <var>ob</var> must not be |
| 87 | <tt class="constant">NULL</tt>. |
| 88 | </dd></dl> |
| 89 | |
| 90 | <P> |
| 91 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject* <b><tt id='l2h-736' xml:id='l2h-736' class="cfunction">PyCell_New</tt></b>(</nobr></td><td>PyObject *<var>ob</var>)</td></tr></table></dt> |
| 92 | <dd> |
| 93 | <div class="refcount-info"> |
| 94 | <span class="label">Return value:</span> |
| 95 | <span class="value">New reference.</span> |
| 96 | </div> |
| 97 | Create and return a new cell object containing the value <var>ob</var>. |
| 98 | The parameter may be <tt class="constant">NULL</tt>. |
| 99 | </dd></dl> |
| 100 | |
| 101 | <P> |
| 102 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject* <b><tt id='l2h-737' xml:id='l2h-737' class="cfunction">PyCell_Get</tt></b>(</nobr></td><td>PyObject *<var>cell</var>)</td></tr></table></dt> |
| 103 | <dd> |
| 104 | <div class="refcount-info"> |
| 105 | <span class="label">Return value:</span> |
| 106 | <span class="value">New reference.</span> |
| 107 | </div> |
| 108 | Return the contents of the cell <var>cell</var>. |
| 109 | </dd></dl> |
| 110 | |
| 111 | <P> |
| 112 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject* <b><tt id='l2h-738' xml:id='l2h-738' class="cfunction">PyCell_GET</tt></b>(</nobr></td><td>PyObject *<var>cell</var>)</td></tr></table></dt> |
| 113 | <dd> |
| 114 | <div class="refcount-info"> |
| 115 | <span class="label">Return value:</span> |
| 116 | <span class="value">Borrowed reference.</span> |
| 117 | </div> |
| 118 | Return the contents of the cell <var>cell</var>, but without checking |
| 119 | that <var>cell</var> is non-<tt class="constant">NULL</tt> and a cell object. |
| 120 | </dd></dl> |
| 121 | |
| 122 | <P> |
| 123 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-739' xml:id='l2h-739' class="cfunction">PyCell_Set</tt></b>(</nobr></td><td>PyObject *<var>cell</var>, PyObject *<var>value</var>)</td></tr></table></dt> |
| 124 | <dd> |
| 125 | Set the contents of the cell object <var>cell</var> to <var>value</var>. This |
| 126 | releases the reference to any current content of the cell. |
| 127 | <var>value</var> may be <tt class="constant">NULL</tt>. <var>cell</var> must be non-<tt class="constant">NULL</tt>; if it is |
| 128 | not a cell object, <code>-1</code> will be returned. On success, <code>0</code> |
| 129 | will be returned. |
| 130 | </dd></dl> |
| 131 | |
| 132 | <P> |
| 133 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>void <b><tt id='l2h-740' xml:id='l2h-740' class="cfunction">PyCell_SET</tt></b>(</nobr></td><td>PyObject *<var>cell</var>, PyObject *<var>value</var>)</td></tr></table></dt> |
| 134 | <dd> |
| 135 | Sets the value of the cell object <var>cell</var> to <var>value</var>. No |
| 136 | reference counts are adjusted, and no checks are made for safety; |
| 137 | <var>cell</var> must be non-<tt class="constant">NULL</tt> and must be a cell object. |
| 138 | </dd></dl> |
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