Another alternative (if we don't want to use __dict__) is to make the descriptor object keep track of the values for each instance itself, in an internal mapping, and return values from this mapping as well.
There is a caveat, though. This mapping cannot just be any dictionary. Since the client class has a reference to the descriptor, and now the descriptor will keep references to the objects that use it, this will create circular dependencies, and, as a result, these objects will never be garbage-collected because they are pointing at each other.
In order to address this, the dictionary has to be a weak key one, as defined in the weakref (WEAKREF 01) module.
In this case, the code for the descriptor might look like ...
