[Numpy-discussion] Silent DeprecationWarnings under Python 2.7 onwards

Ralf Gommers ralf.gommers@googlemail....
Thu Sep 16 08:21:05 CDT 2010

On Wed, Sep 15, 2010 at 10:34 PM, Benjamin Root <ben.root@ou.edu> wrote:

> On Wed, Sep 15, 2010 at 8:28 AM, Ralf Gommers <ralf.gommers@googlemail.com
> > wrote:
>> 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 class to alert users when some feature is going to be withdrawn.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.

Sure, documenting this well and recommending to turn on the warnings for
example once after installation and once before upgrading makes a lot of

Places to document it:
Any others?


> 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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