From c91d67031094cf87ed6677f311ee3541c87ff051 Mon Sep 17 00:00:00 2001 From: Savannah Ostrowski Date: Tue, 9 Jun 2026 10:07:03 -0700 Subject: [PATCH] GH-59633: Clarify dest collisions in argparse docs (GH-150987) (cherry picked from commit 82cb7d4bf62041b75a08628baa1f9fe761fd6a79) Co-authored-by: Savannah Ostrowski --- Doc/library/argparse.rst | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst index 4c588d447a9a7cf..e4a5f4d109b4992 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