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_colorize.can_colorize() raises when sys.stdout is mod_wsgi logger #141570
Description
Bug report
Bug description:
In Fedora, we've been given a slightly incomplete reproducer for a problematic Python 3.14 color-related change in argparse that leads to an exception when Python is used from mod_wsgi. cc @GrahamDumpleton
Apparently the following code is enough to trigger it:
import argparse
parser = argparse.ArgumentParser(add_help=False, color=False)
arg = parser.add_argument('-v', '--verbose', help='verbose', action='store_true', default=False)Looking at GrahamDumpleton/mod_wsgi#890 it seems that mod_wsgi replaces sys.stdout with a custom object that raises OSError on .fileno():
The relevant code in _colorize.can_colorize() does not expect OSError -- it only expects a more specific io.UnsupportedOperation:
Lines 313 to 316 in a2442fd
I don't know if raising OSError from .fileno() in mod_wsgi is OK or not, yet perhaps _colorize.can_colorize() should be more robust and expect either OSError or outright Exception. WDYT?
CPython versions tested on:
3.14
Operating systems tested on:
Linux
Activity
hroncok commentedon Nov 14, 2025
FWIW the docuemntation of fileno says:
That makes me think that expecting
io.UnsupportedOperationis outright wrong.hugovk commentedon Nov 14, 2025
Yes,
OSErrordoes make more sense here, would you like to open a PR?hroncok commentedon Nov 14, 2025
Will do.
hroncok commentedon Nov 14, 2025
FWIW I won't do it right away, because I am thinking how to properly test this. Perhaps by calling
_colorize.can_colorize(file=...)on a custom file-like object.can_colorize: Expect fileno() to raise OSError, as documented
cmaloney commentedon Nov 18, 2025
re:
OSError,io.UnsupportedOperationactually inherits from it so both should work. 👍 on changing to the more generic OSError check.gh-141570: can_colorize: Expect fileno() to raise OSError, as documen…
pythongh-141570: can_colorize: Expect fileno() to raise OSError, as d…
pythongh-141570: can_colorize: Expect fileno() to raise OSError, as d…
[3.13] gh-141570: can_colorize: Expect fileno() to raise OSError, as …
[3.14] gh-141570: can_colorize: Expect fileno() to raise OSError, as …
pythongh-141570: can_colorize: Expect fileno() to raise OSError, as d…
pythongh-141570: can_colorize: Expect fileno() to raise OSError, as d…