Description

garyaviv

opened on May 26, 2025

Issue body actions

Bug report

Bug description:

When the PYTHONWARNINGS message field contains a special character such as . or * it gets quoted as \. or \* so it looses it's regex meaning and never matches. I tested this in 3.8 and 3.13.

PYTHONWARNINGS='ignore:This.*deadlocks:DeprecationWarning' python -c 'import warnings; print(warnings.filters[0])'

yields:

('ignore', re.compile('This\\.\\*deadlocks', re.IGNORECASE), <class 'DeprecationWarning'>, None, 0)

(note the extra backslash is a result of the print statement, doing a repr.)

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-134716: Support regular expressions in -W and PYTHONWARNINGS #138149

Activity

1. garyaviv

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on May 26, 2025
2. picnixz

   added

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   on May 26, 2025
3. picnixz commented on May 26, 2025

   

   picnixz

   on May 26, 2025

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   The docs say:

   In -W and PYTHONWARNINGS, message is a literal string that the start of the warning message must contain (case-insensitively), ignoring any whitespace at the start or end of message

   So I don't think we're meant to support regexes when using -W and PYTHONWARNINGS (but we can when we use the module directly)
4. picnixz

   added

   type-featureA feature request or enhancementA feature request or enhancement

   and removed

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on May 26, 2025
5. picnixz

   changed the title [-]regular expressions in symbol PYTHONWARNINGS don't work[/-] [+]Support regular expressions in `-W` and `PYTHONWARNINGS`[/+] on May 26, 2025
6. garyaviv commented on May 26, 2025

   

   garyaviv

   on May 26, 2025

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   Thank you for clarification.
   My fault. The docs 3.10.7 indeed says -W and PYTHONWARNINGS is a literal string. Prior versions seem to lack this language:

   The warnings filter is initialized by -W options passed to the Python interpreter command line and the PYTHONWARNINGS environment variable.
   <snip>
   Individual warnings filters are specified as a sequence of fields separated by colons:
   action:message:category:module:line
   The meaning of each of these fields is as described in The Warnings Filter.
7. serhiy-storchaka commented on May 30, 2025

   

   serhiy-storchaka

   on May 30, 2025

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   See also #78805, #79101, #86438, #88028. There may be other duplicate issues.

   Reacted by Bénédikt Tran
8. picnixz commented on May 30, 2025

   

   picnixz

   on May 30, 2025

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   Arf, my bad. I'll triage them tomorrow.
9. serhiy-storchaka commented on May 30, 2025

   

   serhiy-storchaka

   on May 30, 2025

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   All of them were closed. AFAIK. only the documentation was updated.

   But I had ideas on how to solve this problem differently, so we can leave this issue for that or reopen one of old issues if they contain more information.
10. serhiy-storchaka

    self-assigned this

    on Aug 25, 2025
11. serhiy-storchaka

    added a commit that references this issue on Aug 25, 2025

    pythongh-134716: Support regular expressions in -W and PYTHONWARNINGS

    dcb9cfd
12. serhiy-storchaka commented on Aug 25, 2025

    

    serhiy-storchaka

    on Aug 25, 2025

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    #138149 implements support of regular expressions. To differentiate them from literal strings, you must surround them by forward slashes.

    Using the original example:

    $ PYTHONWARNINGS='ignore:This.*deadlocks:DeprecationWarning' ./python -c 'import warnings; print(warnings.filters[0])'
    ('ignore', re.compile('This\\.\\*deadlocks', re.IGNORECASE), <class 'DeprecationWarning'>, None, 0)
    $ PYTHONWARNINGS='ignore:/This.*deadlocks/:DeprecationWarning' ./python -c 'import warnings; print(warnings.filters[0])'
    ('ignore', re.compile('This.*deadlocks', re.IGNORECASE), <class 'DeprecationWarning'>, None, 0)
13. serhiy-storchaka commented on Sep 15, 2025

    

    serhiy-storchaka

    on Sep 15, 2025

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    Previous issues which were closed after changing the documentation:

    • -W option and PYTHONWARNINGS env variable does not accept module regexes #78805
    • PYTHONWARNINGS entries are escaped #79101
    • Warning filter message/module documentation is misleading #86438
    • warnings: -W option and PYTHONWARNINGS now use the message as a regex #88028
14. serhiy-storchaka

    added a commit that references this issue on Sep 16, 2025

    gh-134716: Support regular expressions in -W and PYTHONWARNINGS (GH-1…

    cf9ef73
15. serhiy-storchaka

    closed this as completedon Sep 17, 2025

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