class A:
    def foo(self):
        return 1
    def __call__(self):
        return 10
    def cow(self):
        return -1
    def moo(self):
        return -10
    def switch(self):
        self.foo = self.cow
        self.__call__ = self.moo

class B(object):
    def foo(self):
        return 2
    def __call__(self):
        return 20
    def cow(self):
        return -2
    def moo(self):
        return -20
    def switch(self):
        self.foo = self.cow
        self.__call__ = self.moo
        self._B__call__ = self.moo
        setattr(self, '__call__', self.moo)
        setattr(self, '_B__call__', self.moo)
    
class MyMeta(type):
    pass

class C:
    __metaclass__ = MyMeta
    def foo(self):
        return 3
    def __call__(self):
        return 30
    def cow(self):
        return -3
    def moo(self):
        return -30
    def switch(self):
        self.foo = self.cow
        self.__call__ = self.moo

a = A()
b = B()
c = C()

assert a.foo() == 1, a.foo()
assert b.foo() == 2, b.foo()
assert c.foo() == 3, c.foo()
assert a() == 10, a()
assert b() == 20, b()
assert c() == 30, c()

a.switch()
b.switch()
c.switch()

assert a.foo() == -1, a()
assert b.foo() == -2, b()
assert c.foo() == -3, c()
assert a() == -10, a()
assert b() == -20, b()
assert c() == -30, c()

print 'A-OK!'