arsatiki

# class Foo(object): 
#    ... 
# is syntactic sugar for
# Foo = type('Foo', (object,), {...})
# And with a metaclass Meta:
# Bar = Meta('Bar', (object,), {...})

def metafunc(name, bases, dict):
    print "I created a new class %s%s from %s" % (name, bases, dict)
    return type(name, bases, dict)

arsatiki

class Additive(type):
    def __add__(self, x):
        return type("Additive", (self, x), {})

class A(object):
    __metaclass__ = Additive
    def foo(self):
        print "foo"

class B(object):