On Fri, Feb 15, 2008 at 10:26 AM, Phillip J. Eby <[EMAIL PROTECTED]> wrote: > At 09:35 AM 2/15/2008 -0800, Guido van Rossum wrote: > >On Fri, Feb 15, 2008 at 2:12 AM, Nick Craig-Wood <[EMAIL PROTECTED]> wrote: > > > I've just been bitten yet again by the fact you can't have a weakref > > > to a bound method! I find myself wanting to do this whenever I have a > > > registry of callback functions. > > > > > > Could we in py3k either > > > > > > 1) make weakrefs to bound methods work? A weakref to a bound method > > > should mean hold the weakref on the instance and bind the method at > > > the last moment. > > > >I think you're somehow confused about how weakrefs are supposed to > >work. They work fine! > > The use case here is actually to keep the callback around only so > long as the object exists.
Ah, I see. Nick actually wrote this but because I'm so familiar with the concept of a bound method object I didn't see what his actual issue was. Sorry Nick! > There are various ways to do this, of course, that don't require > changing the language or stdlib. One of the simplest (for 2.4 and > up) is to create a callable weakref subclass that emulates a bound > method. Another is to create a bound method whose im_self is a weakref > proxy. > > I've never actually encountered a usecase for keeping a standard > weakref to a standard bound method, though. It's pretty useless, > because bound methods are nearly always immediately disposed of, and > there's no logical place (or reason) to store them. So, Nick's query > is (in effect), can we either: > > 1. make ref(method) create a "weak method" instead, or > > 2. make ref(method) an error instead of useless behavior that gives > you the illusion of working code #2 is easily implemented (just remove the machinery to support weak refs from the bound method object) but the question is, will it break anybody's code -- and if so, do we care enough to break it? (In Py3k, that is.) #1 isn't so easy in terms of how you'd implement it -- I don't think the weakref.ref() call currently has a way to customize what kind of thing you get back. I'd be open for a patch containing working code that can be generalized to other cases. -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
