[Python-Dev] type categories

[Andrew Koenig]

>> Not really.  I can see how an interface can claim that a particular
>> method exists, but not how it can claim that the method implements a
>> function that is antisymmetric and transitive.

Guido> That's done in the docs, usually.  Zope even has the notion of a
Guido> "marker" interface -- an interface that says "this object has property
Guido> such-and-such" but which does not assert any methods or attributes.

So perhaps what I mean by a category is the set of all types that
implement a particular marker interface.