1 .. highlightlang:: c

     2 

     3 .. _allocating-objects:

     4 

     5 Allocating Objects on the Heap

     6 ==============================

     7 

     8 

     9 .. cfunction:: PyObject* _PyObject_New(PyTypeObject *type)

    10 

    11 

    12 .. cfunction:: PyVarObject* _PyObject_NewVar(PyTypeObject *type, Py_ssize_t size)

    13 

    14 

    15 .. cfunction:: void _PyObject_Del(PyObject *op)

    16 

    17 

    18 .. cfunction:: PyObject* PyObject_Init(PyObject *op, PyTypeObject *type)

    19 

    20    Initialize a newly-allocated object *op* with its type and initial reference.

    21    Returns the initialized object.  If *type* indicates that the object

    22    participates in the cyclic garbage detector, it is added to the detector's set

    23    of observed objects. Other fields of the object are not affected.

    24 

    25 

    26 .. cfunction:: PyVarObject* PyObject_InitVar(PyVarObject *op, PyTypeObject *type, Py_ssize_t size)

    27 

    28    This does everything :cfunc:`PyObject_Init` does, and also initializes the

    29    length information for a variable-size object.

    30 

    31 

    32 .. cfunction:: TYPE* PyObject_New(TYPE, PyTypeObject *type)

    33 

    34    Allocate a new Python object using the C structure type *TYPE* and the Python

    35    type object *type*.  Fields not defined by the Python object header are not

    36    initialized; the object's reference count will be one.  The size of the memory

    37    allocation is determined from the :attr:`tp_basicsize` field of the type object.

    38 

    39 

    40 .. cfunction:: TYPE* PyObject_NewVar(TYPE, PyTypeObject *type, Py_ssize_t size)

    41 

    42    Allocate a new Python object using the C structure type *TYPE* and the Python

    43    type object *type*.  Fields not defined by the Python object header are not

    44    initialized.  The allocated memory allows for the *TYPE* structure plus *size*

    45    fields of the size given by the :attr:`tp_itemsize` field of *type*.  This is

    46    useful for implementing objects like tuples, which are able to determine their

    47    size at construction time.  Embedding the array of fields into the same

    48    allocation decreases the number of allocations, improving the memory management

    49    efficiency.

    50 

    51 

    52 .. cfunction:: void PyObject_Del(PyObject *op)

    53 

    54    Releases memory allocated to an object using :cfunc:`PyObject_New` or

    55    :cfunc:`PyObject_NewVar`.  This is normally called from the :attr:`tp_dealloc`

    56    handler specified in the object's type.  The fields of the object should not be

    57    accessed after this call as the memory is no longer a valid Python object.

    58 

    59 

    60 .. cfunction:: PyObject* Py_InitModule(char *name, PyMethodDef *methods)

    61 

    62    Create a new module object based on a name and table of functions, returning the

    63    new module object.

    64 

    65    .. versionchanged:: 2.3

    66       Older versions of Python did not support *NULL* as the value for the *methods*

    67       argument.

    68 

    69 

    70 .. cfunction:: PyObject* Py_InitModule3(char *name, PyMethodDef *methods, char *doc)

    71 

    72    Create a new module object based on a name and table of functions, returning the

    73    new module object.  If *doc* is non-*NULL*, it will be used to define the

    74    docstring for the module.

    75 

    76    .. versionchanged:: 2.3

    77       Older versions of Python did not support *NULL* as the value for the *methods*

    78       argument.

    79 

    80 

    81 .. cfunction:: PyObject* Py_InitModule4(char *name, PyMethodDef *methods, char *doc, PyObject *self, int apiver)

    82 

    83    Create a new module object based on a name and table of functions, returning the

    84    new module object.  If *doc* is non-*NULL*, it will be used to define the

    85    docstring for the module.  If *self* is non-*NULL*, it will passed to the

    86    functions of the module as their (otherwise *NULL*) first parameter.  (This was

    87    added as an experimental feature, and there are no known uses in the current

    88    version of Python.)  For *apiver*, the only value which should be passed is

    89    defined by the constant :const:`PYTHON_API_VERSION`.

    90 

    91    .. note::

    92 

    93       Most uses of this function should probably be using the :cfunc:`Py_InitModule3`

    94       instead; only use this if you are sure you need it.

    95 

    96    .. versionchanged:: 2.3

    97       Older versions of Python did not support *NULL* as the value for the *methods*

    98       argument.

    99 

   100 

   101 .. cvar:: PyObject _Py_NoneStruct

   102 

   103    Object which is visible in Python as ``None``.  This should only be accessed

   104    using the ``Py_None`` macro, which evaluates to a pointer to this object.