>Assuming that A is a new-style class then if they have to be >exactly the same type compare the types
Ah-ha! I didn't know that. >if the 'other' value can be a subclass of self: > > def join(self, other): > if not isinstance(other, type(self)): > raise whatever Simple and neat! >If A is an old-style class then you would have to compare >the __class__ attribute: self.__class__ != other.__class__ That answered my question perfectly. I'll read up on the new style classes and pick whichever of your solutions fits best. Many thanks, Andy. -- http://mail.python.org/mailman/listinfo/python-list
