[Python-Dev] Why is nan != nan?

Greg Ewing greg.ewing at canterbury.ac.nz
Mon Mar 29 01:55:55 CEST 2010

Steven D'Aprano wrote:

> I disagree -- if I ask:
> 3.0 in [1.0, 2.0, float('nan'), 3.0]
> I should get True, not an exception.

Yes, I don't think anyone would disagree that NaN should compare
unequal to anything that isn't a NaN. Problems only arise when
comparing two NaNs.


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