[Python-Dev] Proposal: go back to enabling DeprecationWarning by default (original) (raw)

Yury Selivanov yselivanov.ml at gmail.com
Sun Nov 5 21:20:12 EST 2017

Big +1 from me. The whole point of DeprecationWarnings is to be visible so that they are resolved faster. The current behaviour allows them to go unnoticed for the majority of Python users.

Yury

On Sun, Nov 5, 2017 at 9:05 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:

On the 12-weeks-to-3.7-feature-freeze thread, Jose Bueno & I both mistakenly though the async/await deprecation warnings were missing from 3.6.

They weren't missing, we'd just both forgotten those warnings were off by default (7 years after the change to the default settings in 2.7 & 3.2). So my proposal is simple (and not really new): let's revert back to the way things were in 2.6 and earlier, with DeprecationWarning being visible by default, and app devs having to silence it explicitly during application startup (before they start importing third party modules) if they don't want their users seeing it when running on the latest Python version (e.g. this would be suitable for open source apps that get integrated into Linux distros and use the system Python there). This will also restore the previously clear semantic and behavioural different between PendingDeprecationWarning (hidden by default) and DeprecationWarning (visible by default). As part of this though, I'd suggest amending the documentation for DeprecationWarning [1] to specifically cover how to turn it off programmatically (warnings.simplefilter("ignore",_ _DeprecationWarning)), at the command line (python -W_ _ignore::DeprecationWarning ...), and via the environment (PYTHONWARNINGS=ignore::DeprecationWarning). (Structurally, I'd probably put that at the end of the warnings listing as a short introduction to warnings management, with links out to the relevant sections of the documentation, and just use DeprecationWarning as the specific example) Cheers, Nick. [1] https://docs.python.org/3/library/exceptions.html#DeprecationWarning -- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia

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