On 2016-01-27 21:01, Ralf Gommers wrote:
On Wed, Jan 27, 2016 at 7:26 PM, Sebastian Berg
<sebast...@sipsolutions.net> wrote:
Hi all,
in my PR about warnings suppression, I currently also have a commit
which bumps the warning stacklevel to two (or three), i.e. use:
warnings.warn(..., stacklevel=2)
(almost) everywhere. This means that for example (take only the
empty
warning):
np.mean([])
would not print:
/usr/lib/python2.7/dist-packages/numpy/core/_methods.py:55:
RuntimeWarning: Mean of empty slice.
warnings.warn("Mean of empty slice.", RuntimeWarning)
but instead print the actual `np.mean([])` code line (the repetition
of
the warning command is always a bit funny).
The advantage is nicer printing for the user.
The disadvantage would probably mostly be that existing warning
filters
that use the `module` keyword argument, will fail.
Any objections/thoughts about doing this change to try to better
report
the offending code line?
This has annoyed me for a long time, it's hard now to figure out where
warnings really come from. Especially when running something large
like scipy.test(). So +1.
Frankly, I am not sure whether there might be
a python standard about this, but I would expect that for a library
such as numpy, it makes sense to change. But, if downstream uses
warning filters with modules, we might want to reconsider for
example.
There probably are usages of `module`, but I'd expect that it's used a
lot less than `category` or `message`. A quick search through the
scipy repo gave me only a single case where `module` was used, and
that's in deprecated weave code so soon the count is zero. Also, even
for relevant usage, nothing will break in a bad way - some more noise
or a spurious test failure in numpy-using code isn't the end of the
world I'd say.
One issue will be how to keep this consistent. `stacklevel` is used so
rarely that new PRs will always omit it for new warnings. Will we just
rely on code review, or would a private wrapper around `warn` to use
inside numpy plus a test that checks that the wrapper is used
everywhere be helpful here?
Yeah, I mean you could add tests for the individual functions in
principle.
I am not sure if adding an alias helps much, how are we going to test
that
warnings.warn is not being used? Seems like quite a bit of voodoo
necessary
for that.
- Sebastian
Ralf
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