[Python-Dev] PEP 565: Show DeprecationWarning in main (original) (raw)

Guido van Rossum guido at python.org
Tue Dec 5 13:24:43 EST 2017

On Tue, Dec 5, 2017 at 9:59 AM, Victor Stinner <victor.stinner at gmail.com> wrote:

2017-12-05 16:50 GMT+01:00 Guido van Rossum <guido at python.org>: > Honestly, I didn't completely follow what Victor thinks of the PEP -- his > post seemed mostly about promoting his own -X dev flag.

-X dev is similar (but different) than -W default: show warnings which are hidden by default otherwise. -W default works on Python 2.7 and 3.6. > I have nothing > against that flag but I don't see how its existence is relevant to the PEP, > which is about giving users who don't even know they are Python developers a > hint when they are using deprecated features (for which there always must be > a shiny new replacement!). I disagree that users of an application is supposed to "handle" deprecation warnings: report them to the developer, or even try to fix them. IHMO these warnings (hidden by default) were introduced for developers of the application.

But the whole point of the PEP is that it only warns about deprecations in code over which the user has control -- likely main is their own code, and they can handle it.

My point is that I prefer to keep the status quo: continue to hide deprecation warnings, but promote existing solutions like -W default to display these warnings, teach to developers how to see and fix these warnings.

If they import a 3rd party module which does something deprecated, the user won't see any deprecation warnings.

Even for developers, I'm not sure that only showing warnings in main_ is useful, since more and more application use a _main module which is a thin entry point : import + function call (ex: "from app import main; main()").

And that's intentional -- such developers are supposed to actively test their code, and deprecations will be shown to them by the unittest framework. Having a minimal main implies that their users won't see any deprecation warnings.

> Therefore I am planning to accept it by the end of this week unless more objections are voiced.

It's ok if we disagree. I just wanted to share my opinion on this issue ;-)

I just worry that your opinion might be based on a misunderstanding of the proposal. If we agree on what the PEP actually proposed to change, and how that will affect different categories of users and developers, I am okay with disagreement.

-- --Guido van Rossum (python.org/~guido) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20171205/9b8e6a68/attachment.html>

More information about the Python-Dev mailing list