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gh-139946: distinguish stdout or stderr when colorizing output in argparse #140495

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Merged

savannahostrowski merged 6 commits into python:main from frostming:fix/colorize-argparse

Dec 8, 2025

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gh-139946: distinguish stdout or stderr when colorizing output in argparse #140495

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1c6c898

fix: distinguish stdout or stderr when colorizing output in argparse

frostming Oct 23, 2025

6d10257

📜🤖 Added by blurb_it.

blurb-it[bot] Oct 23, 2025

6c02905

fix: make _get_formatter to take file argument to avoid calling set_c…

frostming Oct 27, 2025

8ed66a2

add tests for the change

frostming Oct 27, 2025

8518870

fix: handle backward-compatibility for format_* methods

frostming Nov 12, 2025

6dd3d3d

Merge branch 'main' into fix/colorize-argparse

savannahostrowski Dec 8, 2025

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44 changes: 30 additions & 14 deletions 44 Lib/argparse.py

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -89,8 +89,8 @@
		import os as _os
		import re as _re
		import sys as _sys

		from gettext import gettext as _, ngettext
		from gettext import gettext as _
		from gettext import ngettext

		SUPPRESS = '==SUPPRESS=='

Expand Down Expand Up		@@ -191,10 +191,10 @@ def __init__(

		self._set_color(False)

		def _set_color(self, color):
		def _set_color(self, color, *, file=None):
		from _colorize import can_colorize, decolor, get_theme

		if color and can_colorize():
		if color and can_colorize(file=file):
		self._theme = get_theme(force_color=True).argparse
		self._decolor = decolor
		else:
Expand Down Expand Up		@@ -1675,7 +1675,7 @@ def _get_optional_kwargs(self, args, *kwargs):
		option_strings = []
		for option_string in args:
		# error on strings that don't start with an appropriate prefix
		if not option_string[0] in self.prefix_chars:
		if option_string[0] not in self.prefix_chars:
		raise ValueError(
		f'invalid option string {option_string!r}: '
		f'must start with a character {self.prefix_chars!r}')
Expand Down Expand Up		@@ -2455,7 +2455,7 @@ def _parse_optional(self, arg_string):
		return None

		# if it doesn't start with a prefix, it was meant to be positional
		if not arg_string[0] in self.prefix_chars:
		if arg_string[0] not in self.prefix_chars:
		return None

		# if the option string is present in the parser, return the action
Expand Down Expand Up		@@ -2717,14 +2717,16 @@ def _check_value(self, action, value):
		# Help-formatting methods
		# =======================

		def format_usage(self):
		formatter = self._get_formatter()
		def format_usage(self, formatter=None):
Comment thread frostming marked this conversation as resolved. Resolved Uh oh! There was an error while loading. Please reload this page.
		if formatter is None:
		formatter = self._get_formatter()
		formatter.add_usage(self.usage, self._actions,
		self._mutually_exclusive_groups)
		return formatter.format_help()

		def format_help(self):
		formatter = self._get_formatter()
		def format_help(self, formatter=None):
		if formatter is None:
		formatter = self._get_formatter()

		# usage
		formatter.add_usage(self.usage, self._actions,
Expand All		@@ -2746,9 +2748,9 @@ def format_help(self):
		# determine help from format above
		return formatter.format_help()

		def _get_formatter(self):
		def _get_formatter(self, file=None):
		formatter = self.formatter_class(prog=self.prog)
		formatter._set_color(self.color)
		formatter._set_color(self.color, file=file)
		return formatter

		def _get_validation_formatter(self):
Expand All		@@ -2765,12 +2767,26 @@ def _get_validation_formatter(self):
		def print_usage(self, file=None):
		if file is None:
		file = _sys.stdout
		self._print_message(self.format_usage(), file)
		formatter = self._get_formatter(file=file)
		try:
		usage_text = self.format_usage(formatter=formatter)
		except TypeError:
		# Backward compatibility for formatter classes that
		# do not accept the 'formatter' keyword argument.
		usage_text = self.format_usage()
		self._print_message(usage_text, file)

		def print_help(self, file=None):
		if file is None:
		file = _sys.stdout
		self._print_message(self.format_help(), file)
		formatter = self._get_formatter(file=file)
		try:
		help_text = self.format_help(formatter=formatter)
		except TypeError:
		# Backward compatibility for formatter classes that
		# do not accept the 'formatter' keyword argument.
		help_text = self.format_help()
		self._print_message(help_text, file)

		def _print_message(self, message, file=None):
		if message:
Expand Down

34 changes: 34 additions & 0 deletions 34 Lib/test/test_argparse.py

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -7558,6 +7558,40 @@ def test_error_and_warning_not_colorized_when_disabled(self):
		self.assertNotIn('\x1b[', warn)
		self.assertIn('warning:', warn)

		def test_print_help_uses_target_file_for_color_decision(self):
		parser = argparse.ArgumentParser(prog='PROG', color=True)
		parser.add_argument('--opt')
		output = io.StringIO()
		calls = []

		def fake_can_colorize(*, file=None):
		calls.append(file)
		return file is None

		with swap_attr(_colorize, 'can_colorize', fake_can_colorize):
		parser.print_help(file=output)

		self.assertIs(calls[-1], output)
		self.assertIn(output, calls)
		self.assertNotIn('\x1b[', output.getvalue())

		def test_print_usage_uses_target_file_for_color_decision(self):
		parser = argparse.ArgumentParser(prog='PROG', color=True)
		parser.add_argument('--opt')
		output = io.StringIO()
		calls = []

		def fake_can_colorize(*, file=None):
		calls.append(file)
		return file is None

		with swap_attr(_colorize, 'can_colorize', fake_can_colorize):
		parser.print_usage(file=output)

		self.assertIs(calls[-1], output)
		self.assertIn(output, calls)
		self.assertNotIn('\x1b[', output.getvalue())


		class TestModule(unittest.TestCase):
		def test_deprecated__version__(self):
Expand Down

1 change: 1 addition & 0 deletions 1 Misc/NEWS.d/next/Library/2025-10-23-06-38-35.gh-issue-139946.HZa5hu.rst

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Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Distinguish stdout and stderr when colorizing output in argparse module.

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