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[3.14] GH-155009: Preserve argparse prog for programmatic module-as-main execution (GH-155199) #155201

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Merged
savannahostrowski merged 1 commit into from
Aug 5, 2026
+19 −0
Merged

[3.14] GH-155009: Preserve argparse prog for programmatic module-as-main execution (GH-155199) #155201

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3 changes: 3 additions & 0 deletions Lib/argparse.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1829,6 +1829,9 @@ def _prog_name(prog=None):
if modspec is None:
# simple script
return _os.path.basename(arg0)
if modspec.name != '__main__' and arg0 != modspec.origin:
# named module executed as main without altering sys.argv[0]
return _os.path.basename(arg0)
py = _os.path.basename(_sys.executable)
if modspec.name != '__main__':
# imported module or package
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13 changes: 13 additions & 0 deletions Lib/test/test_argparse.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7128,6 +7128,19 @@ def test_module(self, compiled=False):
def test_module_compiled(self):
self.test_module(compiled=True)

def test_module_as_main_without_altering_argv(self):
basename = 'module' + os_helper.FS_NONASCII
modulename = f'{self.dirname}.{basename}'
self.make_script(self.dirname, basename)
runner_source = textwrap.dedent(f'''\
import runpy
runpy._run_module_as_main({modulename!r}, alter_argv=False)
''')
runner = script_helper.make_script(
self.dirname, 'runner', runner_source)
self.check_usage(os.path.basename(runner), runner,
PYTHONPATH=os.curdir)

def test_package(self, compiled=False):
basename = 'subpackage' + os_helper.FS_NONASCII
packagename = f'{self.dirname}.{basename}'
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-08-05-02-36-18.gh-issue-155009.YiJAiP.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix :class:`argparse.ArgumentParser` to preserve the program name from
``sys.argv[0]`` when a named module is executed as the main program without
replacing ``sys.argv[0]``.
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