[Python-Dev] type categories

[Andrew Koenig]

>>>>>> "Oren" == Oren Tirosh <oren-py-d@hishome.net> writes:
Oren> I would like to be able to declare that I need an object
Oren> with a specific interface even if the object was written
Oren> long before and I don't want to modify an existing library
Oren> just to make it conform to my interface names.

Nathan> class InterfaceWrapper(ExistingClass, AbstractInterfaceClass):
Nathan>       pass

Nathan> I'm not saying this is a good idea :), but I believe this problem is
Nathan> already solvable in the current language.

Not quite.  You are creating a new class with the desired property,
but it can sometimes be desirable to assert properties about
types that already exist.

For example, suppose I invent a GroupUnderPlus property for
types for which the + operator has group properties.  I would
like to be able to say that int has that property, and not
have to derive a new class from int in order to do so.


-- 
Andrew Koenig, ark@research.att.com, http://www.research.att.com/info/ark