[Numpy-discussion] Warning: invalid value encountered in subtract

[Keith Goodman]

On Tue, Nov 30, 2010 at 1:41 PM, Skipper Seabold <jsseabold at gmail.com> wrote:
> On Tue, Nov 30, 2010 at 1:34 PM, Keith Goodman <kwgoodman at gmail.com> wrote:
>> After upgrading from numpy 1.4.1 to 1.5.1 I get warnings like
>> "Warning: invalid value encountered in subtract" when I run unit tests
>> (or timeit) using "python -c 'blah'" but not from an interactive
>> session. How can I tell the warnings to go away?
>
> If it's this type of floating point related stuff, you can use np.seterr
>
> In [1]: import numpy as np
>
> In [2]: np.log(1./np.array(0))
> Warning: divide by zero encountered in divide
> Out[2]: inf
>
> In [3]: orig_settings = np.seterr()
>
> In [4]: np.seterr(all="ignore")
> Out[4]: {'divide': 'print', 'invalid': 'print', 'over': 'print', 'under': 'ignor
> e'}
>
> In [5]: np.log(1./np.array(0))
> Out[5]: inf
>
> In [6]: np.seterr(**orig_settings)
> Out[6]: {'divide': 'ignore', 'invalid': 'ignore', 'over': 'ignore', 'under': 'ig
> nore'}
>
> In [7]: np.log(1./np.array(0))
> Warning: divide by zero encountered in divide
> Out[7]: inf
>
> I have been using the orig_settings so that I can take over the
> control of this from the user and then set it back to how it was.

Thank, Skipper. That works. Do you wrap it in a try...except? And then
raise whatever brought you to the exception? Sounds like a pain.

Is it considered OK for a package to change the state of np.seterr if
there is an error? Silly question. I'm just looking for an easy fix.