partial.py

import functools
class Foo(object):
    def __init__(self):
        self.__dict__["overridden_methods"] = {}

    def __setattr__(self, key, value):
        """Blindly assume that if we're setting attrs it's with new methods"""
        self.overridden_methods[key] = value

    def __getattr__(self, key):
        if key in self.overridden_methods:
            def _(*args, **kwargs):
                return self.overridden_methods[key](self, *args, **kwargs)
            return _
        else:
            return super(Foo,self).__getattr__(key)

foo = Foo()
def func(self, value):
    print repr(self)
    print value

foo.foo = func
foo.foo("bar")