test for nan

[David M. Cooke]

At some point, Skip Montanaro <skip at pobox.com> wrote:

>     John> Is there a better way to test for NaN than
>
>     John>    str(p1)=='nan'
>
>     John> where p1 is a float?
>
> Saw this in the list archives earlier today:
>
>     >>> inf = float("1e9999")
>     >>> inf
>     Inf
>     >>> nan = inf-inf
>     >>> nan
>     NaN
>     >>> p1 = 5.0
>     >>> p1 == nan
>     False

The last line doesn't work for me:

Python 2.3.3 (#2, Feb 24 2004, 09:29:20) 
[GCC 3.3.3 (Debian)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> inf = float('1e9999')
>>> inf
inf
>>> nan = inf - inf
>>> nan
nan
>>> p1 = 5.0
>>> p1 == nan
True

hmmm... Have to admit that looks funny.

-- 
|>|\/|<
/--------------------------------------------------------------------------\
|David M. Cooke
|cookedm(at)physics(dot)mcmaster(dot)ca