class MyDesc(object):
 
    def __init__(self):
        self.val = None
 
    def __get__(self, instance, owner):
        print "MyDesc.__get__"
        return self.val
 
    def __set__(self, instance, value):
        print "MyDesc.__set__"
        self.val = value
 
class A(object):
    foo1 = MyDesc()
 
class MyObj(A):
 
    foo = MyDesc()
 
    def __init__(self, bar):
        object.__setattr__(self, 'names', dict(
            bar=bar,
        ))
        object.__setattr__(self, 'new_names', dict())
 
#    def __setattr__(self, name, value):
#        print "MyObj.__setattr__ for %s" % name
#        for cls in self.__class__.__mro__ + (self, ):
#            if name in cls.__dict__:
#                return object.__setattr__(self, name, value)
#        print 'New name', name, value
#        self.new_names[name] = value
 
    def __setattr__(self, name, value):
        print "MyObj.__setattr__ for %s" % name
        try:
            object.__getattribute__(self, name)
        except AttributeError:
            print 'New name', name, value
            self.new_names[name] = value
        else:
            object.__setattr__(self, name, value)
 
    def __getattr__(self, name):
        print "MyObj.__getattr__ for %s" % name
 
        if name in self.new_names:
            return self.new_names[name]
 
        if name in self.names:
            return self.names[name]
 
        raise AttributeError(name)
 
if __name__ == "__main__":
    o = MyObj('bar-init')
 
    print o.bar
    o.bar = 'baz'
    print o.bar
    o.bar = 'baz2'
    print o.bar
 
    o.bazbar = 'barbaz'
    print o.bazbar
 
    o.foo = 'quux'
    print o.foo
 
    o.foo1 = 'quux1'
    print o.foo1
 
    o.bar = 'baz'
    print o.bar

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