confused about __new__

[K. Richard Pixley]

I'm confused about the following.  The idea here is that the set of 
instances of some class are small and finite, so I'd like to create them 
at class creation time, then hijack __new__ to simply return one of the 
preexisting classes instead of creating a new one each call.

This seems to work in python3, but fails in python2 with:

     Foo(23)
TypeError: unbound method __Foo__new__() must be called with Foo 
instance as first argument (got type instance instead)

I don't understand.  Can anyone explain?

--rich
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