[Python-3000] ABC PEP isinstance issue Was: PEP 31XX: A Type Hierarchy for Numbers (and other algebraic entities)

[Phillip J. Eby]

At 04:43 PM 4/25/2007 -0700, Guido van Rossum wrote:
>This is a very good point. Perhaps we can come up with a way to make
>isinstance and issubclass into something like GFs (without requiring
>the whole GF machinery).
>
>I'll think about it some more.

__special__ methods are how Python currently defines built-in GFs, so 
perhaps __isinstance__ and __issubclass__ slots (and their __r*__ 
counterparts) should suffice.

OTOH, the old PEP 246 (implemented by both PyProtocols and zope.interface) 
just uses __conform__ and __adapt__ and basically works the same way as an 
__isinstance__/__risinstance__ pair...