stuff.py

class A(object):
    @property
    def x(self):
        return self._x
    @x.setter
    def x(self, value):
        self._x = value

class B(A):
    @A.x.getter
    def x(self):
        return self._x * 2

hi = A()
bar = B()
hi.x = 'hello'
print hi.x # prints hello
bar.x = 'world'
print bar.x # prints worldworld