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.
-
int
PyWeakref_Check
(ob)¶ Return true if ob is either a reference or proxy object.
New in version 2.2.
-
int
PyWeakref_CheckRef
(ob)¶ Return true if ob is a reference object.
New in version 2.2.
-
int
PyWeakref_CheckProxy
(ob)¶ Return true if ob is a proxy object.
New in version 2.2.
-
PyObject*
PyWeakref_NewRef
(PyObject *ob, PyObject *callback)¶ - Return value: New reference.
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 raiseTypeError
.New in version 2.2.
-
PyObject*
PyWeakref_NewProxy
(PyObject *ob, PyObject *callback)¶ - Return value: New reference.
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 raiseTypeError
.New in version 2.2.
-
PyObject*
PyWeakref_GetObject
(PyObject *ref)¶ - Return value: Borrowed reference.
Return the referenced object from a weak reference, ref. If the referent is no longer live, returns
Py_None
.New in version 2.2.
Warning
This function returns a borrowed reference to the referenced object. This means that you should always call
Py_INCREF()
on the object except if you know that it cannot be destroyed while you are still using it.
-
PyObject*
PyWeakref_GET_OBJECT
(PyObject *ref)¶ - Return value: Borrowed reference.
Similar to
PyWeakref_GetObject()
, but implemented as a macro that does no error checking.New in version 2.2.