> > Gustavo J. A. M. Carneiro wrote: > > > I have come across a situation where I find the current weak > > > references interface for extension types insufficient. > > > > > > Currently you only have a tp_weaklistoffset slot, pointing to a > > > PyObject with weak references. However, in my case[1] I _really_ need > > > to be notified when a weak reference is dereferenced.
I find reading through the bug discussion a bit difficult to understand your use case. Could you explain it here? If you can't explain it you certainly won't get your problem solved! :-) > > > What happens now > > > is that, when you call a weakref object, a simple Py_INCREF is done on > > > the referenced object. It would be easy to implement a new slot to > > > contain a function that should be called when a weak reference is > > > dereferenced. Or, alternatively, a slot or class attribute that > > > indicates an alternative type that should be used to create weak > > > references: instead of the builtin weakref object, a subtype of it, so > > > you can override tp_call. > > > > > > Does this sounds acceptable? [Jim Fulton] > > Since you can now (as of 2.4) subclass the weakref.ref class, you should be > > able to > > do this yourself in Python. See for example, weakref.KeyedRef. > > I know I can subclass it, but it doesn't change anything. If people > keep writing code like weakref.ref(myobj) instead of myweakref(myobj), > it still won't work. > > I wouldn't want to have to teach users of the library that they need > to use an alternative type; that seldom doesn't work. > > Now, if there was a place in the type that contained information like > > "for creating weak references of instances of this type, use this > weakref class" > > and weakref.ref was smart enough to lookup this type and use it, only > _then_ it could work. Looks what you're looking for is a customizable factory fuction. -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
