Metaclass madness.

metamadness.py

import functools as ft

class IAmAPig(type):
    @classmethod
    def _make_aux(cls, base, k, attribute):
        super_meth = getattr(base, k, None)
        if super_meth is not None:
            @ft.wraps(attribute)
            def aux(self, *args, **kwargs):
                super_meth(self, *args, **kwargs)
                return attribute(self, *args, **kwargs)
            return aux
        else:
            return None

    @classmethod
    def _customize(cls, base, dct):
        updated = {}
        for k, attribute in dct.iteritems():
            if callable(attribute):
                updated_attribute = cls._make_aux(base, k, attribute)
                if updated_attribute is not None:
                    updated[k] = updated_attribute
        dct.update(updated)

    @classmethod
    def _find_base(cls, name, bases, dct):
        for base in bases:
            if isinstance(base, IAmAPig):
                return base
        else:
            return None

    def __new__(cls, name, bases, dct):
        base = cls._find_base(name, bases, dct)
        if base is not None:
            cls._customize(base, dct)
        return super(IAmAPig, cls).__new__(cls, name, bases, dct)

class Base(object):
    __metaclass__ = IAmAPig
    def foo(self):
        print 'Base'


class Child(Base):
    def foo(self):
        print 'Child'

    def bar(self):
        print 'Bar'


c = Child()
c.foo()
c.bar()