[Raymond]
> assuming basic invariants.  In 2.6, all of the following are always
> true:
>
>   assert a in [a]
>   assert a in (a,)
>   assert a in set([a])
>   assert [a].count(a) == 1

And these are all still true in 3.0 as well, aren't they?

In any case, you've convinced me.  I withdraw my comment
about the Python 3.0 behaviour being the right one.