[Numpy-discussion] the difference of np.nan, np.NaN, np.NAN?
Olivier Delalleau
shish@keba...
Fri Oct 14 05:53:35 CDT 2011
2011/10/14 Matthew Brett <matthew.brett@gmail.com>
> Hi,
>
> On Fri, Oct 14, 2011 at 4:33 AM, Chao YUE <chaoyuejoy@gmail.com> wrote:
> > Dear all,
> >
> > is there any difference between np.nan, np.NaN and np.NAN? they really
> > confuse me....
> > they are all Not a Number?
> >
> > In [75]: np.nan==np.NaN
> > Out[75]: False
> >
> > In [77]: np.NaN==np.NAN
> > Out[77]: False
>
> The nan value is not equal to itself:
>
> In [70]: np.nan == np.nan
> Out[70]: False
>
> See:
>
> http://en.wikipedia.org/wiki/NaN
>
> But:
>
> In [71]: np.isnan(np.nan)
> Out[71]: True
>
> In [72]: np.isnan(np.NAN)
> Out[72]: True
>
> In [73]: np.isnan(np.NaN)
> Out[73]: True
>
> Best,
>
> Matthew
>
Also on my computer:
>>> numpy.nan is numpy.NAN
True
>>> numpy.nan is numpy.NaN
True
So they really are the same. But you shouldn't rely on this (always use
numpy.isnan to test for nan-ness).
-=- Olivier
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