[SciPy-user] Re: nan puzzle
Robert Kern
rkern at ucsd.edu
Wed Jul 13 22:53:34 EDT 2005
Grant Edwards wrote:
> On 2005-07-13, Alan G Isaac <aisaac at american.edu> wrote:
>>Anyway, now I cannot replicate the problem.
>
> I still don't understand what the problem is (or was).
His original code had
>>> z = [0, 1, nan]
>>> x = z[2]
>>> x is nan
False
Since "is" evaluates based on pointer comparisons and putting something
in a list or extracting it again by indexing ought to preserve those
pointers, that result shouldn't happen for any object, nan or otherwise.
Of course, "x is nan" is a pretty useless operation as you point out,
and one really should be using some kind of isnan() function. Preferably
implemented by someone other than one's self. :-)
--
Robert Kern
rkern at ucsd.edu
"In the fields of hell where the grass grows high
Are the graves of dreams allowed to die."
-- Richard Harter
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