runtimewarning: invalid value encountered in true_divide

I'd also consider looking at catch_warnings which is a context manager which automatically resets the original filterwarnings function: > import warnings Read carefully the documentation for filterwarnings since it allows you to filter only the warning you want and has other options. print 'Warning was raised as an exception!'

Once you actually have a warning, you can use the warnings module to control how the warnings should be treated: > import warnings

Use terr(all='warn'), which will transform the printed warning in a real warning and you'll be able to use the above solution to localize this change in behaviour.

This however changes the behaviour of all the operations, so it's a pretty big change in behaviour.

Use terr(all='raise') which will directly raise the exception.

This means that the warning you see is not a real warning, but it's just some characters printed to stdout(see the documentation for seterr).

Warning: divide by zero encountered in divide _main_:1: RuntimeWarning: divide by zero encountered in divide

It seems that your configuration is using the print option for terr: > import numpy as np

Runtimewarning: invalid value encountered in true_divide