On Mar 8, 5:32 am, Lie Ryan <lie.1...@gmail.com> wrote: > Mel wrote: > > wrote: > > >> Steven D'Aprano <st...@pearwood.info> writes: > >>> It is never > >>> correct to avoid using "is" when you need to compare for identity. > >> When is it ever necessary to compare for identity? > > > Ho-hum. MUDD game. > > > def broadcast (sender, message): > > for p in all_players: > > if p is not sender: > > p.tell (message) # don't send a message to oneself > > Since in a MUD game, a player would always have a unique username, I'd > rather compare with that. It doesn't rely on some internals. There is > very, very rare case where 'is' is really, really needed.
Well, by that criterion you can dismiss almost anything. Of course you can assign unique ids to most objects and perform your identity tests that way. The point is that sometimes you do need to test for the identity of the object, not merely the equivalent semantic value. If, faced with this problem (and I'm guessing you haven't faced it much) your approach is always to define a unique id, so that you can avoid ever having to use the "is" operator, be my guest. As for me, I do program in the sort of areas where identity testing is common, and I don't care to define ids just to test for identity alone, so for me "is" is useful. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
