Implementing interfaces with inheritance, good or bad?

[Tripp Scott]

I just saw:

  http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/68445

in which interfaces are implemented using class, and a class 
implementing one or more interfaces subclasses the interfaces 
class(es). Now suppose class C implements two Interfaces, I1 and 
I2. Both interfaces define an operation foo(). In one case, I 
want to instantiate C because of I1, and in other case, because 
I need a class that implements I2. How does C implement both 
foo() operations (since foo() will be implemented as a method)? 
And how do I tell C that I want I1, or I2? With an argument to 
__init__? Any other way?

I prefer providing Interface lookup via other mechanism, like 
with the __implements__ class attribute as done in Zope's 
Interface module. But are there any advantages of interfaces 
being done with inheritance?

t