cpython/Doc/c-api/allocation.rst

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.. highlightlang:: c
.. _allocating-objects:
Allocating Objects on the Heap
==============================
.. cfunction:: PyObject* _PyObject_New(PyTypeObject *type)
.. cfunction:: PyVarObject* _PyObject_NewVar(PyTypeObject *type, Py_ssize_t size)
.. cfunction:: PyObject* PyObject_Init(PyObject *op, PyTypeObject *type)
Merged revisions 71898-71900,71910,71914-71919 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r71898 | jeroen.ruigrok | 2009-04-25 16:24:30 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71899 | jeroen.ruigrok | 2009-04-25 16:27:00 +0200 (za, 25 apr 2009) | 3 lines The type for ppos has been Py_ssize_t since 2.5, reflect this in the documentation. ........ r71900 | jeroen.ruigrok | 2009-04-25 16:28:02 +0200 (za, 25 apr 2009) | 2 lines Reformat paragraph. ........ r71910 | jeroen.ruigrok | 2009-04-25 19:59:03 +0200 (za, 25 apr 2009) | 4 lines Issue #4129: Belatedly document which C API functions had their argument(s) or return type changed from int or int * to Py_ssize_t or Py_ssize_t * as this might cause problems on 64-bit platforms. ........ r71914 | jeroen.ruigrok | 2009-04-25 20:31:20 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71915 | jeroen.ruigrok | 2009-04-25 20:46:03 +0200 (za, 25 apr 2009) | 2 lines Issue #4129: Document more int -> Py_ssize_t changes. ........ r71916 | jeroen.ruigrok | 2009-04-25 20:53:48 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71917 | jeroen.ruigrok | 2009-04-25 20:57:32 +0200 (za, 25 apr 2009) | 2 lines Reference to an int type, whereas it's a Py_ssize_t as the synopsis states. ........ r71918 | jeroen.ruigrok | 2009-04-25 21:04:15 +0200 (za, 25 apr 2009) | 2 lines Since I edited this file, reformat for future edits. ........ r71919 | jeroen.ruigrok | 2009-04-25 21:10:52 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........
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Initialize a newly-allocated object *op* with its type and initial
reference. Returns the initialized object. If *type* indicates that the
object participates in the cyclic garbage detector, it is added to the
detector's set of observed objects. Other fields of the object are not
affected.
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.. cfunction:: PyVarObject* PyObject_InitVar(PyVarObject *op, PyTypeObject *type, Py_ssize_t size)
This does everything :cfunc:`PyObject_Init` does, and also initializes the
length information for a variable-size object.
.. cfunction:: TYPE* PyObject_New(TYPE, PyTypeObject *type)
Merged revisions 71898-71900,71910,71914-71919 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r71898 | jeroen.ruigrok | 2009-04-25 16:24:30 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71899 | jeroen.ruigrok | 2009-04-25 16:27:00 +0200 (za, 25 apr 2009) | 3 lines The type for ppos has been Py_ssize_t since 2.5, reflect this in the documentation. ........ r71900 | jeroen.ruigrok | 2009-04-25 16:28:02 +0200 (za, 25 apr 2009) | 2 lines Reformat paragraph. ........ r71910 | jeroen.ruigrok | 2009-04-25 19:59:03 +0200 (za, 25 apr 2009) | 4 lines Issue #4129: Belatedly document which C API functions had their argument(s) or return type changed from int or int * to Py_ssize_t or Py_ssize_t * as this might cause problems on 64-bit platforms. ........ r71914 | jeroen.ruigrok | 2009-04-25 20:31:20 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71915 | jeroen.ruigrok | 2009-04-25 20:46:03 +0200 (za, 25 apr 2009) | 2 lines Issue #4129: Document more int -> Py_ssize_t changes. ........ r71916 | jeroen.ruigrok | 2009-04-25 20:53:48 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71917 | jeroen.ruigrok | 2009-04-25 20:57:32 +0200 (za, 25 apr 2009) | 2 lines Reference to an int type, whereas it's a Py_ssize_t as the synopsis states. ........ r71918 | jeroen.ruigrok | 2009-04-25 21:04:15 +0200 (za, 25 apr 2009) | 2 lines Since I edited this file, reformat for future edits. ........ r71919 | jeroen.ruigrok | 2009-04-25 21:10:52 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........
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Allocate a new Python object using the C structure type *TYPE* and the
Python type object *type*. Fields not defined by the Python object header
are not initialized; the object's reference count will be one. The size of
the memory allocation is determined from the :attr:`tp_basicsize` field of
the type object.
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.. cfunction:: TYPE* PyObject_NewVar(TYPE, PyTypeObject *type, Py_ssize_t size)
Merged revisions 71898-71900,71910,71914-71919 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r71898 | jeroen.ruigrok | 2009-04-25 16:24:30 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71899 | jeroen.ruigrok | 2009-04-25 16:27:00 +0200 (za, 25 apr 2009) | 3 lines The type for ppos has been Py_ssize_t since 2.5, reflect this in the documentation. ........ r71900 | jeroen.ruigrok | 2009-04-25 16:28:02 +0200 (za, 25 apr 2009) | 2 lines Reformat paragraph. ........ r71910 | jeroen.ruigrok | 2009-04-25 19:59:03 +0200 (za, 25 apr 2009) | 4 lines Issue #4129: Belatedly document which C API functions had their argument(s) or return type changed from int or int * to Py_ssize_t or Py_ssize_t * as this might cause problems on 64-bit platforms. ........ r71914 | jeroen.ruigrok | 2009-04-25 20:31:20 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71915 | jeroen.ruigrok | 2009-04-25 20:46:03 +0200 (za, 25 apr 2009) | 2 lines Issue #4129: Document more int -> Py_ssize_t changes. ........ r71916 | jeroen.ruigrok | 2009-04-25 20:53:48 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71917 | jeroen.ruigrok | 2009-04-25 20:57:32 +0200 (za, 25 apr 2009) | 2 lines Reference to an int type, whereas it's a Py_ssize_t as the synopsis states. ........ r71918 | jeroen.ruigrok | 2009-04-25 21:04:15 +0200 (za, 25 apr 2009) | 2 lines Since I edited this file, reformat for future edits. ........ r71919 | jeroen.ruigrok | 2009-04-25 21:10:52 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........
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Allocate a new Python object using the C structure type *TYPE* and the
Python type object *type*. Fields not defined by the Python object header
are not initialized. The allocated memory allows for the *TYPE* structure
plus *size* fields of the size given by the :attr:`tp_itemsize` field of
*type*. This is useful for implementing objects like tuples, which are
able to determine their size at construction time. Embedding the array of
fields into the same allocation decreases the number of allocations,
improving the memory management efficiency.
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.. cfunction:: void PyObject_Del(PyObject *op)
Releases memory allocated to an object using :cfunc:`PyObject_New` or
Merged revisions 71898-71900,71910,71914-71919 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r71898 | jeroen.ruigrok | 2009-04-25 16:24:30 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71899 | jeroen.ruigrok | 2009-04-25 16:27:00 +0200 (za, 25 apr 2009) | 3 lines The type for ppos has been Py_ssize_t since 2.5, reflect this in the documentation. ........ r71900 | jeroen.ruigrok | 2009-04-25 16:28:02 +0200 (za, 25 apr 2009) | 2 lines Reformat paragraph. ........ r71910 | jeroen.ruigrok | 2009-04-25 19:59:03 +0200 (za, 25 apr 2009) | 4 lines Issue #4129: Belatedly document which C API functions had their argument(s) or return type changed from int or int * to Py_ssize_t or Py_ssize_t * as this might cause problems on 64-bit platforms. ........ r71914 | jeroen.ruigrok | 2009-04-25 20:31:20 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71915 | jeroen.ruigrok | 2009-04-25 20:46:03 +0200 (za, 25 apr 2009) | 2 lines Issue #4129: Document more int -> Py_ssize_t changes. ........ r71916 | jeroen.ruigrok | 2009-04-25 20:53:48 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........ r71917 | jeroen.ruigrok | 2009-04-25 20:57:32 +0200 (za, 25 apr 2009) | 2 lines Reference to an int type, whereas it's a Py_ssize_t as the synopsis states. ........ r71918 | jeroen.ruigrok | 2009-04-25 21:04:15 +0200 (za, 25 apr 2009) | 2 lines Since I edited this file, reformat for future edits. ........ r71919 | jeroen.ruigrok | 2009-04-25 21:10:52 +0200 (za, 25 apr 2009) | 2 lines Reformat prior to editing. ........
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:cfunc:`PyObject_NewVar`. This is normally called from the
:attr:`tp_dealloc` handler specified in the object's type. The fields of
the object should not be accessed after this call as the memory is no
longer a valid Python object.
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.. cvar:: PyObject _Py_NoneStruct
Object which is visible in Python as ``None``. This should only be accessed
using the :cmacro:`Py_None` macro, which evaluates to a pointer to this
object.
.. seealso::
:cfunc:`PyModule_Create`
To allocate and create extension modules.