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

Victor Stinner victor.stinner at gmail.com
Tue Dec 5 12:59:49 EST 2017

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.

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.

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()").

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 ;-)

Victor

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