Python wierdness

[Michael Hudson]

"Roger H" <rhyde99 at email.msn.com> writes:
[snip]
>     >>> x = 0.3
>     >>>
>     >>> # Let's check whether x modulo 0.1 is equal to 0.1:
>     ...
>     >>> x % 0.1
>     0.1
>     >>>
>     >>> # Obviously, x modulo 0.1 is indeed equal to 0.1.
>     ... # If we pass it to foo(), we should see "bar", right?
[snip]
> What's going on here, and how could one get around it?

Floating point is going on here.  Python 2.0 is more helpful in this
regard:

>>> 0.3 % 0.1
0.099999999999999978
>>> 0.1
0.10000000000000001
>>> 0.3 % 0.1 - 0.1
-2.7755575615628914e-17

Comparing floats for equality is always fraught.  Enjoy :-) (I may be
a mathematician, but you aren't going to catch me doing numerical
analysis...)

Cheers,
M.

-- 
  I'd certainly be shocked to discover a consensus.  ;-)
                                      -- Aahz Maruch, comp.lang.python