python nan != nan

Question

Python 2.7.3 (default, Aug  1 2012, 05:14:39) 
[GCC 4.6.3] on linux2
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>>> x =          


        

Answer 1

For the "where" part of your questions, look starting at line 391 in Objects/floatobject.c in the Python 2.7.3 source tree. A brief discussion is given about the behavior of NaN == NaN with the implementation following.

With respect to other cases that exhibit similar behavior, it is certainly possible. I have not done an exhaustive search of the libraries however, so I can't give a definitive answer.