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authorGeorg Brandl <georg@python.org>2008-01-20 09:30:57 (GMT)
committerGeorg Brandl <georg@python.org>2008-01-20 09:30:57 (GMT)
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Split C API docs in Py3k branch.
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+.. highlightlang:: 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.
+
+
+.. cfunction:: int PyWeakref_Check(ob)
+
+ Return true if *ob* is either a reference or proxy object.
+
+
+.. cfunction:: int PyWeakref_CheckRef(ob)
+
+ Return true if *ob* is a reference object.
+
+
+.. cfunction:: int PyWeakref_CheckProxy(ob)
+
+ Return true if *ob* is a proxy object.
+
+
+.. cfunction:: 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`.
+
+
+.. cfunction:: 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`.
+
+
+.. cfunction:: PyObject* PyWeakref_GetObject(PyObject *ref)
+
+ Return the referenced object from a weak reference, *ref*. If the referent is
+ no longer live, returns ``None``.
+
+
+.. cfunction:: PyObject* PyWeakref_GET_OBJECT(PyObject *ref)
+
+ Similar to :cfunc:`PyWeakref_GetObject`, but implemented as a macro that does no
+ error checking.