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v3.10.20
Doc/c-api/weakref.rst
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Hugo van Kemenade
[3.10] gh-101100: Document PyObject_ClearWeakRefs and gzip's name (#103002)
25 мар 2023, 10:44
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25 мар 2023, 10:44
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.. highlight:: c .. _weakrefobjects: Weak Reference Objects ---------------------- Python supports *weak references* as first-class objects. There are two specific object types which directly implement weak references. The first is a simple reference object, and the second acts as a proxy for the original object as much as it can. .. c:function:: int PyWeakref_Check(ob) Return true if *ob* is either a reference or proxy object. This function always succeeds. .. c:function:: int PyWeakref_CheckRef(ob) Return true if *ob* is a reference object. This function always succeeds. .. c:function:: int PyWeakref_CheckProxy(ob) Return true if *ob* is a proxy object. This function always succeeds. .. c:function:: PyObject* PyWeakref_NewRef(PyObject *ob, PyObject *callback) Return a weak reference object for the object *ob*. This will always return a new reference, but is not guaranteed to create a new object; an existing reference object may be returned. The second parameter, *callback*, can be a callable object that receives notification when *ob* is garbage collected; it should accept a single parameter, which will be the weak reference object itself. *callback* may also be ``None`` or ``NULL``. If *ob* is not a weakly referencable object, or if *callback* is not callable, ``None``, or ``NULL``, this will return ``NULL`` and raise :exc:`TypeError`. .. c:function:: PyObject* PyWeakref_NewProxy(PyObject *ob, PyObject *callback) Return a weak reference proxy object for the object *ob*. This will always return a new reference, but is not guaranteed to create a new object; an existing proxy object may be returned. The second parameter, *callback*, can be a callable object that receives notification when *ob* is garbage collected; it should accept a single parameter, which will be the weak reference object itself. *callback* may also be ``None`` or ``NULL``. If *ob* is not a weakly referencable object, or if *callback* is not callable, ``None``, or ``NULL``, this will return ``NULL`` and raise :exc:`TypeError`. .. c:function:: PyObject* PyWeakref_GetObject(PyObject *ref) Return the referenced object from a weak reference, *ref*. If the referent is no longer live, returns :const:`Py_None`. .. note:: This function returns a :term:`borrowed reference` to the referenced object. This means that you should always call :c:func:`Py_INCREF` on the object except when it cannot be destroyed before the last usage of the borrowed reference. .. c:function:: PyObject* PyWeakref_GET_OBJECT(PyObject *ref) Similar to :c:func:`PyWeakref_GetObject`, but implemented as a macro that does no error checking. .. c:function:: void PyObject_ClearWeakRefs(PyObject *object) This function is called by the :c:member:`~PyTypeObject.tp_dealloc` handler to clear weak references. This iterates through the weak references for *object* and calls callbacks for those references which have one. It returns when all callbacks have been attempted.