[Python-Dev] Proposal: go back to enabling DeprecationWarning by default

[Nathaniel Smith]

On Sun, Nov 5, 2017 at 9:38 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> We've been running the current experiment for 7 years, and the main
> observable outcome has been folks getting surprised by breaking
> changes in CPython releases, especially folks that primarily use
> Python interactively (e.g. for data analysis), or as a scripting
> engine (e.g. for systems administration).

It's also caused lots of projects to switch to using their own ad hoc
warning types for deprecations, e.g. off the top of my head:

https://github.com/matplotlib/matplotlib/blob/6c51037864f9a4ca816b68ede78207f7ecec656c/lib/matplotlib/cbook/deprecation.py#L5
https://github.com/numpy/numpy/blob/d75b86c0c49f7eb3ec60564c2e23b3ff237082a2/numpy/_globals.py#L45
https://github.com/python-trio/trio/blob/f50aa8e00c29c7f2953b7bad38afc620772dca74/trio/_deprecate.py#L16

So in some ways the change has actually made it *harder* for end-user
applications/scripts to hide all deprecation warnings, because for
each package you use you have to somehow figure out which
idiosyncratic type it uses, and filter them each separately.

(In any changes though please do keep in mind that Python itself is
not the only one issuing deprecation warnings. I'm thinking in
particular of the filter-based-on-Python-version idea. Maybe you could
have subclasses like Py35DeprecationWarning and filter on those?)

-n

-- 
Nathaniel J. Smith -- https://vorpus.org