[Python-3000] Revised PEP 3119 (Abstract Base Classes)

[Phillip J. Eby]

At 06:34 PM 5/15/2007 -0700, Guido van Rossum wrote:
> > Have I missed something? It would seem that when dealing with ABCs
> > that provide concrete methods, "isinstance(x, SomeABC) == True" is
> > useless.
>
>The intention is that you shouldn't register such cases. This falls
>under the consenting-adults rule.

Not only that, but the presence of the isinstance()/issubclass() 
hooks actually means that if you want to create your own "Role" or 
"Interface" types that actually *verify* your requirements, you can do so!