Rebinding __setattr__

[Jan Schilleman]

Hi all,

I am trying to redefine __setattr__.

The base class is in a library (actually, it is 
win32com.client.DispatchBaseClass) and I do not want to touch it. My problem 
is exemplified below. To my surprise, __setattr__ and __str__ behave 
differently; I can redefine __str__ and the inherited __str__ is still the 
redefined one. But redefining __setattr__ on the base class does not get 
inherited. In Base.__dict__ the __setattr__ is the one I expected, but it is 
not called from B.

What is the problem? Is __setattr__ cached somewhere [and not updated?]?

class Base:

    def __setattr__(self, attr, value):
        print 'Base __setattr__'
        self.__dict__[attr] = value

    def __str__(self):
        return "Base"

class A(Base): pass
class B(Base): pass

def __setattr__(self, attr, value):
    print 'alternative __setattr__'
    self.__dict__[attr] = value

def __str__(self):
    return "Alternative"

a = A()
b = B()

for i in (1, 2):
    print
    print 'run', i
    print

    print Base.__dict__
    print A.__dict__
    print B.__dict__

    print
    print 'a:', a
    a.a1 = 1

    print 'b:', b
    b.b1 = 1

    setattr(Base, '__setattr__', __setattr__)
    setattr(A, '__setattr__', __setattr__)
    setattr(Base, '__str__', __str__)
    setattr(A, '__str__', __str__)