[Python-Dev] PyObject_RichCompareBool identity shortcut (original) (raw)

Glenn Linderman v+python at g.nevcal.com
Thu Apr 28 06:52:55 CEST 2011

On 4/27/2011 7:31 PM, Stephen J. Turnbull wrote:

Glenn Linderman writes:

> I would not, however expect the original case that was described: > >>> nan = float('nan') > >>> nan == nan > False > >>> [nan] == [nan] > True # also True in tuples, dicts, etc. Are you saying you would expect that

nan = float('nan') a = [1, ..., 499, nan, 501, ..., 999] # meta-ellipsis, not Ellipsis a == a False ??

Yes, absolutely. Once you understand the definition of NaN, it certainly cannot be True. a is a, but a is not equal to a.

I wouldn't even expect

a = [1, ..., 499, float('nan'), 501, ..., 999] b = [1, ..., 499, float('nan'), 501, ..., 999] a == b False but I guess I have to live with that. While I wouldn't apply it to other people, I have to admit Raymond's aphorism applies to me (the surprising thing is not the behavior of NaNs, but that I'm surprised by anything that happens in the presence of NaNs!)

The only thing that should happen in the presence of NaNs is more NaNs :)

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