gistfile1.py

class TestDescriptor(object):
    def __init__(self, initval, name):
        self.val = initval
        self.name = name

    def __get__(self, obj, objtype):
        print "retrieving", self.name
        return self.val

    def __set__(self, obj, val):
        print "updating", self.name
        self.val = val

class MyClass(object):
    x = TestDescriptor(10, "x")

class MySubclass(MyClass):
    def __init__(self):
        print super(MyClass, self).x

x = MySubclass()