How to get rid of specific warning messages in python while keeping all other warnings as normal?

Question

I am doing some simple math recessively in a python script and am getting the follow warning:

“Warning: divide by zero encountered in divide”.

To provide some context, I am taking two values and trying to find the percent difference in value (a - b) / a and if its above a certain range then process it, but sometimes the value of a or b is zero.

I want to get rid of this specific warning (at a specific line) but all the information I have found so far seems to show me how to stop all warnings (which I do not want).

When I used to write shell scripts, I could do something like this

code...
more code 2 > error.txt
even more code

In that example, I would get the warnings for the ‘code’ and ‘even more code’ command but not for the second line.

Is this possible?

Asked By: Lostsoul

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Source

Answer 1

I’d avoid the division-by-zero in the first place:

if a == 0:
    # Break out early

# Otherwise the ratio makes sense

If you do want to squash that particular numpy warning on a single line, numpy provides a way:

with numpy.errstate(divide='ignore'):
    # The problematic line

Answered By: Blender

Answer 2

If Scipy is using the warnings module, then you can suppress specific warnings. Try this at the beginning of your program:

import warnings
warnings.filterwarnings("ignore", message="divide by zero encountered in divide")

If you want this to apply to only one section of code, then use the warnings context manager:

import warnings
with warnings.catch_warnings():
    warnings.filterwarnings("ignore", message="divide by zero encountered in divide")
    # .. your divide-by-zero code ..

Answered By: Ned Batchelder

Answer 3

Blenders answer is perfectly fitting the problem. Maybe someone is interested in another general approach to catch specific warnings with either regex or the line number:

surpress a warning caused by a specific line, here line 113:

import warnings
warnings.simplefilter('ignore',lineno=113)

This approach has the disadvantage, that each time you change something in the code you need to readjust the lineno. The other option is to catch a warning using regex. The following code will return

import warnings
warnings.filterwarnings('ignore', message='.*show', )
warnings.warn('Do not do this!')
warnings.warn('Do not show this message')
>>> UserWarning: Do not do this!
        warnings.warn('Do not do this!')

The dot before the *-symbol is neccessary as otherwise an error is returned

error: nothing to repeat

which is discussed in this thread

Answered By: Jakob

How to get rid of specific warning messages in python while keeping all other warnings as normal?

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