https://github.com/python/cpython/commit/82cb7d4bf62041b75a08628baa1f9fe761fd6a79
commit: 82cb7d4bf62041b75a08628baa1f9fe761fd6a79
branch: main
author: Savannah Ostrowski <[email protected]>
committer: savannahostrowski <[email protected]>
date: 2026-06-09T10:07:03-07:00
summary:
GH-59633: Clarify dest collisions in argparse docs (#150987)
files:
M Doc/library/argparse.rst
diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
index 4c588d447a9a7c..e4a5f4d109b499 100644
--- a/Doc/library/argparse.rst
+++ b/Doc/library/argparse.rst
@@ -1372,6 +1372,11 @@ behavior::
>>> parser.parse_args('--foo XXX'.split())
Namespace(bar='XXX')
+Multiple arguments may share the same ``dest``. By default, the value from the
+last such argument given on the command line wins. Use ``action='append'`` to
+collect values from all of them into a list instead. For conflicting *option
+strings* rather than ``dest`` names, see conflict_handler_.
+
.. versionchanged:: 3.15
Single-dash long option now takes precedence over short options.
@@ -1780,6 +1785,11 @@ Subcommands
present, and when the ``b`` command is specified, only the ``foo`` and
``baz`` attributes are present.
+ If a subparser defines an argument with the same ``dest`` as the parent
+ parser, the two share a single namespace attribute, so the parent's value
+ won't be retained. Users should give them distinct ``dest`` values to
+ keep both.
+
Similarly, when a help message is requested from a subparser, only the help
for that particular parser will be printed. The help message will not
include parent parser or sibling parser messages. (A help message for each
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