spell method chaining?

[Robin Becker]

I wish to create wrapped classes dynamically and have the wrapper class
refer to the base wrapee class methods.

def gen(B):
    class W(B):
        def __init__(self):
            B.__init__(self)
    return W

this works if nested scopes is on so that the reference to B in the
__init__ refers to the argument of gen, but it fails without it unless B
happens to be a global. I thought of using self.__class__.__bases__[0]
to refer to the dynamic base B, but then that fails if I use the
resultant class as a base class.

ie if I try

def gen(B):
    class W(B):
        def __init__(self):
            self.__class__bases__.__init__(self)
    return W

I get trouble (infinite looping) with gen(gen(B))()

What is the correct way for dynamic classes to refer to their immediate
base class methods to allow method chaining etc.
-- 
Robin Becker