[Numpy-discussion] Silent DeprecationWarnings under Python 2.7 onwards

Benjamin Root ben.root@ou....
Wed Sep 15 09:34:24 CDT 2010

On Wed, Sep 15, 2010 at 8:28 AM, Ralf Gommers

> On Fri, Sep 10, 2010 at 12:05 AM, Peter <
> numpy-discussion@maubp.freeserve.co.uk> wrote:
>> Hi all,
>> NumPy currently makes extensive use of the DeprecationWarning
>> class to alert users when some feature is going to be withdrawn.
>> However, as of Python 2.7, the DeprecationWarning is silent by
>> default, see:
>> http://docs.python.org/library/warnings.html#updating-code-for-new-versions-of-python
>> This makes sense to me for deprecation warnings from Python
>> itself or the standard library - after all, Python 2.7 is the last of the
>> Python 2.x series.
> The reason for the change is explained in the paragraph you link to, 2.7
> being the final minor release in the 2.x series isn't it.
> There are many other packages/programs built on numpy, the user/developer
> distinction can be made in the same way as for Python itself. I fail to see
> a reason not to follow the lead of the Python core developers here.
> Cheers,
> Ralf
I have to agree a bit with Peter.  I do understand the rationale of Python's
position, however, I have to wonder what is the point of DeprecationWarning
if it doesn't get displayed?  The warning is supposed to give a heads-up to
the developer to modify their code.

Now, the argument can be made that a python developer should know to run
python with those warnings unmuted.  And I would agree for "true", career
programmers.  However, numpy/scipy/matplotlib have become environments unto
themselves, catered to converts from Matlab, R, S+ and other such
languages.  I would argue that many of the "developers" are not typical
programmers with proper development habits/skills.  Many (myself included)
are graduate students in scientific fields unrelated to computer science.  I
have to wonder how many of them would even be aware of the differences
between python versions  (or even which version they are using!).

Anyway, my point is that the deprecation warnings are very valuable to
display and that we need to keep in mind the audience that SciPy has.  Maybe
we don't necessarily turn them on by default (somehow), but maybe the
documentation should highly recommend that they get turned on, thereby
raising awareness on the part of the user.

There is a side-benefit to mentioning the muted warnings issue in the
documentation.  If a developer later complains that a feature was removed
without any deprecation notices, we could simply point to the documentation
and say that we recommended turning the warnings on.

My 2 cents,
Ben Root
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