evil-patch.py

GLOBAL = 'main'


import foo
import types


def p(self, x):
    return 'p: fixed ' + GLOBAL
foo.Parent.p = types.FunctionType(p.__code__, foo.Parent.p.im_func.__globals__, argdefs=foo.Parent.p.im_func.__defaults__)
def c(self, x):
    return 'child.c: fixed ' + GLOBAL
foo.Parent.c = types.FunctionType(p.__code__, foo.Child.__dict__['c'].__globals__, argdefs=foo.Child.__dict__['c'].__defaults__)
def qux(x):
    return 'qux: fixed ' + GLOBAL
foo.qux = types.FunctionType(qux.__code__, foo.qux.__globals__, argdefs=foo.qux.__defaults__)


if __name__ == '__main__':
    foo.main()

foo.py

GLOBAL = 'library'


class Parent(object):
    def p(self, x=1):
        return 'p: buggy ' + GLOBAL
    def c(self, x=1):
        return 'c: buggy ' + GLOBAL


class Child(Parent):
    def p(self, x=1):
        return 'child.' + Parent.p(self)
    def c(self, x=1):
        return 'child.' + Parent.c(self)


def qux(x=1):
    return 'qux: buggy ' + GLOBAL


def main():
    print(Child().p())
    print(Child().c())
    print(qux())


if __name__ == '__main__':
    main()