1.. highlight:: c 2 3.. _cell-objects: 4 5Cell Objects 6------------ 7 8"Cell" objects are used to implement variables referenced by multiple scopes. 9For each such variable, a cell object is created to store the value; the local 10variables of each stack frame that references the value contains a reference to 11the cells from outer scopes which also use that variable. When the value is 12accessed, the value contained in the cell is used instead of the cell object 13itself. This de-referencing of the cell object requires support from the 14generated byte-code; these are not automatically de-referenced when accessed. 15Cell objects are not likely to be useful elsewhere. 16 17 18.. c:type:: PyCellObject 19 20 The C structure used for cell objects. 21 22 23.. c:var:: PyTypeObject PyCell_Type 24 25 The type object corresponding to cell objects. 26 27 28.. c:function:: int PyCell_Check(ob) 29 30 Return true if *ob* is a cell object; *ob* must not be ``NULL``. 31 32 33.. c:function:: PyObject* PyCell_New(PyObject *ob) 34 35 Create and return a new cell object containing the value *ob*. The parameter may 36 be ``NULL``. 37 38 39.. c:function:: PyObject* PyCell_Get(PyObject *cell) 40 41 Return the contents of the cell *cell*. 42 43 44.. c:function:: PyObject* PyCell_GET(PyObject *cell) 45 46 Return the contents of the cell *cell*, but without checking that *cell* is 47 non-``NULL`` and a cell object. 48 49 50.. c:function:: int PyCell_Set(PyObject *cell, PyObject *value) 51 52 Set the contents of the cell object *cell* to *value*. This releases the 53 reference to any current content of the cell. *value* may be ``NULL``. *cell* 54 must be non-``NULL``; if it is not a cell object, ``-1`` will be returned. On 55 success, ``0`` will be returned. 56 57 58.. c:function:: void PyCell_SET(PyObject *cell, PyObject *value) 59 60 Sets the value of the cell object *cell* to *value*. No reference counts are 61 adjusted, and no checks are made for safety; *cell* must be non-``NULL`` and must 62 be a cell object. 63