Currently python evaluates infinity as equal to itself in my tests (2.6.2 and 3.0.1+
from ubuntu). I'm not entirely sure whether the behaviour of 'inf == inf' is specified
by IEEE 754, but it leads to results like:

>>> 1e400
inf
>>> 1e400 == 1e500
True

And hence unittests which use tests like

if not (math.fabs(value1 - value2) <= 0.00000001 *
max(math.fabs(value1),math.fabs(value2))):
    fail

don't always fail when they should (when a value is inf).

This is a specific example (and probably not the recommended way of testing
values in any case), but I think "inf != inf" is generally considered the correct
behaviour. (Although maybe this is left over from the PEP 42 / PEP 754 mess; I
wasn't able to find the current status of implementing IEEE 754 behaviour in
python.)