Re: Observer implementations
Tobias Weber wrote: In article mailman.1631.1245160392.8015.python-l...@python.org, Mike C. Fletcher mcfle...@vrplumber.com wrote: See PyDispatcher for code to do this. That was the original problem. Got it now: if used inside the class definition dispatcher.connect will raise cannot create weak reference to 'classmethod' object. Outside (using Class.method) it works fine. Ah, I think you've got a logic problem there. The classmethod during class creation has no reference to the class being created, so if you were to call *that* thing it would blow up: class x( object ): @classmethod def y( cls, text ): print text y( 'No you do not!' ) if you were to create a reference to *that* thing (the decorated un-bound class method) it would never have the binding for cls, so it wouldn't do anything. The correct way IMO to bind after-class-creation (e.g. by a class decorator or metaclass) where you reference a bound class method. If you *really* want to do it this way, you can do something like this: class x( object ): @classmethod def y( cls, value ): pass dispatcher.connect( lambda *args: x.y( *args ), signal='hello' ) but ick. HTH, Mike -- Mike C. Fletcher Designer, VR Plumber, Coder http://www.vrplumber.com http://blog.vrplumber.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Observer implementations
Tobias Weber wrote: ... No time to reinvent the wheel I'd still need to know how to weakref a classmethod See PyDispatcher for code to do this. PyDispatcher, at least, is not abandoned, it would be more accurate to say finished. I use it in OpenGLContext (extensively), but I haven't had to change anything in a rather long time. It pretty much just works. Enjoy, Mike -- Mike C. Fletcher Designer, VR Plumber, Coder http://www.vrplumber.com http://blog.vrplumber.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Observer implementations
Tobias Weber wrote: Hi, how to use the Observer pattern in Python? Implement it in your classes? I found PubSub and PyDispatcher, both of which are abandoned. [...] I haven't searched for these, but googling for python observer pattern yields http://code.activestate.com/recipes/131499/ and this seems like a good inspiritation for owns own implementation. -- Gerhard -- http://mail.python.org/mailman/listinfo/python-list
Re: Observer implementations
On Jun 15, 5:22 pm, Tobias Weber t...@gmx.net wrote: In article mailman.1584.1245073461.8015.python-l...@python.org, Gerhard Häring g...@ghaering.de wrote: Implement it in your classes? No time to reinvent the wheel Hmm, observer pattern seems to be one of those things simple enough that reimplementing the wheel might actually be less work than adapting a third-party implementation. But I'll leave that decision to you. I'd still need to know how to weakref a classmethod I can't imagine why you would need to weak reference a class method, since they usually live forever along with the class. But again, you are doing it so you would know. I can't think of an easy way to do it without metaclass programming. Unless you are trying to create a weakref to a bound classmethod. I'd say that's still pretty useless: bound classmethods only keep alive classes and classmethods, which both live forever, and bound classmethods are lightweight and hardly worth the effort. Maybe show us what you need to weak reference classmethods for and we can help you better. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Re: Observer implementations
On Mon, 15 Jun 2009 15:29:34 +0200, Tobias Weber wrote: Despite the confusion all those are useable, but I ran into the problem that I can't register a @classmethod because weakref doesn't like them. What do you mean by weakref not liking class methods? This seems to work OK on python 2.6 class C(object): @classmethod def cm(cls): return Class method of + str(cls) cm = C.cm print cm() # Outputs: # Class method of class '__main__.C' w = weakref.ref(cm) print w # Outputs: # weakref at 0x1a362b8; to 'instancemethod' at 0x7ff1cc9ebb40 (cm) print w() # Outputs: # bound method type.cm of class '__main__.C' print w()() # Outputs: # Class method of class '__main__.C' del cm print w # Outputs: # weakref at 0x1a362b8; dead -- http://mail.python.org/mailman/listinfo/python-list
