From: Michał Górny <mgorny@gentoo.org>
Date: Sun, 1 Jun 2025 05:56:56 +0000 (+0200)
Subject: gh-134970: Fix exception message in argparse module (GH-134971)
X-Git-Tag: v3.15.0a1~1426
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=965c48056633d3f4b41520c8cd07f0275f00fb4c;p=thirdparty%2FPython%2Fcpython.git

gh-134970: Fix exception message in argparse module (GH-134971)

Fix the "unknown action" exception in argparse.ArgumentParser.add_argument_group()
to correctly replace the action class.
---

diff --git a/Lib/argparse.py b/Lib/argparse.py
index d1a6350c3fda..83258cf3e0f3 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -1534,7 +1534,7 @@ class _ActionsContainer(object):
         action_name = kwargs.get('action')
         action_class = self._pop_action_class(kwargs)
         if not callable(action_class):
-            raise ValueError('unknown action {action_class!r}')
+            raise ValueError(f'unknown action {action_class!r}')
         action = action_class(**kwargs)
 
         # raise an error if action for positional argument does not
diff --git a/Misc/NEWS.d/next/Library/2025-05-31-12-08-12.gh-issue-134970.lgSaxq.rst b/Misc/NEWS.d/next/Library/2025-05-31-12-08-12.gh-issue-134970.lgSaxq.rst
new file mode 100644
index 000000000000..20f53569ef45
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-05-31-12-08-12.gh-issue-134970.lgSaxq.rst
@@ -0,0 +1,3 @@
+Fix the "unknown action" exception in
+:meth:`argparse.ArgumentParser.add_argument_group` to correctly replace the
+action class.