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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.
- 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
orNULL
. If ob is not a weakly-referencable object, or if callback is not callable,None
, orNULL
, this will returnNULL
and raiseTypeError
.
- 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
orNULL
. If ob is not a weakly-referencable object, or if callback is not callable,None
, orNULL
, this will returnNULL
and raiseTypeError
.
- 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
.Note
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.