On Mon, May 26, 2008 at 4:11 PM, Raymond Hettinger <python@rcn.com> wrote:
Deque's do not support count(), insert() or __iadd__(). They should not be registered.
If it doesn't implement the MutableSequence protocol it still is a Sized container. However currently it's not registered as a container.
Seems useless to me. I don't think the intent of the ABC pep was to mandate that every class that defines __len__ must be registered as Sized.
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.
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. -- --Guido van Rossum (home page: http://www.python.org/~guido/)