test for nan

[Peter Maas]

John Hunter wrote:
> I have a C extension module that is returning some doubles.  When the
> doubles get out of range, the numbers print as 'nan'.
> 
> Is there a better way to test for NaN than
> 
>    str(p1)=='nan'
> 
> where p1 is a float?
> 
> python2.3
> 
> Thanks,
> John Hunter
> 

As far as I know NaN is th only value that yields false when compared
to itself. This leads to

def isNaN(x):
     return (x == x) == False

Mit freundlichen Gruessen,

Peter Maas

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