I _was_ using xrange as sets representing (potentially large) ranges of ints. Example:
positive = xrange(1, sys.maxint)
if num in positive: ...
I didt follow the iterators discussion: would this continue to work?
No, it would break.
Since there was a off-by-one bug for 'if num in xrange()' in Pyhon2.0 my code already has been rewritten.