Weak Reference Objects — Python documentation
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Python/docs/3.8/c-api/weakref
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.
- int PyWeakref_CheckRef(ob)
- Return true if ob is a reference object.
- int PyWeakref_CheckProxy(ob)
- Return true if ob is a proxy object.
- 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 raise TypeError.
- 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 raise TypeError.
- PyObject *PyWeakref_GetObject(PyObject *ref)
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.
- Similar to PyWeakref_GetObject(), but implemented as a macro that does no error checking.