It turns out that if you define __slots__, and make assignments to attributes in the class definition, they're read-only as far as instances of that class are concerned.
Which I would think means one can't do as follows, but it seems to work:
>>> class Foo:
... a = "quux"
... __slots__ = ("a")
... def setA(self, newa):
... Foo.a = newa
...
>>> f = Foo()
>>> f.a
'quux'
>>> f.setA("blah")
>>> f.a
'blah'
>>> Foo.a
'blah'
>>> f.a = "quuuux"
>>> f.a
'quuuux'
>>> Foo.a
'blah'
Maybe that's new in the newest bleeding edge version? I only have 2.2c1 still.
