Weak Reference Objects¶

Python supportsweak references as first-class objects. There are twospecific object types which directly implement weak references. The first is asimple reference object, and the second acts as a proxy for the original objectas much as it can.

intPyWeakref_Check(ob)¶

Return true ifob is either a reference or proxy object. This functionalways succeeds.

intPyWeakref_CheckRef(ob)¶

Return true ifob is a reference object. This function always succeeds.

intPyWeakref_CheckProxy(ob)¶

Return true ifob is a proxy object. This function always succeeds.

PyObject*PyWeakref_NewRef(PyObject *ob,PyObject *callback)¶

Return value: New reference.

Return a weak reference object for the objectob. This will always returna new reference, but is not guaranteed to create a new object; an existingreference object may be returned. The second parameter,callback, can be acallable object that receives notification whenob is garbage collected; itshould accept a single parameter, which will be the weak reference objectitself.callback may also beNone orNULL. Ifob is not aweakly-referencable object, or ifcallback 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 objectob. This will alwaysreturn a new reference, but is not guaranteed to create a new object; anexisting proxy object may be returned. The second parameter,callback, canbe a callable object that receives notification whenob is garbagecollected; it should accept a single parameter, which will be the weakreference object itself.callback may also beNone orNULL. Ifobis not a weakly-referencable object, or ifcallback 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 isno longer live, returnsPy_None.

Note

This function returns aborrowed reference to the referenced object.This means that you should always callPy_INCREF() on the objectexcept if you know that it cannot be destroyed while you are stillusing it.

PyObject*PyWeakref_GET_OBJECT(PyObject *ref)¶

Return value: Borrowed reference.

Similar toPyWeakref_GetObject(), but implemented as a macro that does noerror checking.