On Tue, May 27, 2008 at 12:16 PM, Armin Ronacher <[EMAIL PROTECTED]> wrote: > Hi, > > Guido van Rossum <guido <at> python.org> writes: > >> There's no need to register as Sized -- the Sized ABC recognizes >> classes that define __len__ automatically. The Container class does >> the same looking for __contains__. Since the deque class doesn't >> implement __contains__, it is not considered a Container -- correctly >> IMO. > True. deque doesn't implement __contains__. However "in" still works > because of the __iter__ fallback.
Sure, but that fallback is slow, and intentionally does not trigger the 'Container' ABC. > So from the API's perspective it's > still compatible, even though it doesn't implement it. The same probably > affects old style iterators (__getitem__ with index). One could argue that > they are still iterable or containers, but that's harder to check so > probably not worth the effort. The ABCs do not intend to capture partial behavioral compatibility that way -- the intent is to capture interface (in the duck typing sense). Whether __iter__ is a good enough substitute for __contains__ depends on a lot of things -- surely for a huge list it isn't, and for an iterator it isn't either (since it modifies the iterator's state). >> >> Another issue is that builtin types don't accept ABCs currently. For >> >> example >> >> set() | SomeSet() gives a TypeError, SomeSet() | set() however works. >> > >> > Pandora's Box -- sure you want to open it? >> >> In 3.0 I'd like to; this was my original intent. In 2.6 I think it's >> not worth the complexity, though I won't complain. > I would love to help on that as I'm very interested in that feature. Please do submit patches! -- --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
