good answer.... 2011/10/14 Matthew Brett

Hi,

On Fri, Oct 14, 2011 at 4:33 AM, Chao YUE 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 _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion

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On Fri, Oct 14, 2011 at 11:53 AM, Olivier Delalleau wrote:

2011/10/14 Matthew Brett

...

Hi,

On Fri, Oct 14, 2011 at 4:33 AM, Chao YUE 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).

They are the same, just not equal to each other (or even to themselves). As for the different NaN names in numpy namespace, I think this is for historical reason (maybe because python itself used to print nan differently on different platforms, although this should not be the case anymore since python 2.6). David