https://github.com/python/cpython/commit/9dc11d887dacd4370e106f677d0649b100452e7d
commit: 9dc11d887dacd4370e106f677d0649b100452e7d
branch: main
author: Serhiy Storchaka <[email protected]>
committer: savannahostrowski <[email protected]>
date: 2026-08-05T09:14:01-07:00
summary:
gh-155043: Support copy.replace() for argparse.Namespace (#155049)
files:
A Misc/NEWS.d/next/Library/2026-08-01-19-04-00.gh-issue-155043.Ar1Nsp.rst
M Doc/library/argparse.rst
M Lib/argparse.py
M Lib/test/test_argparse.py
diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
index e4a5f4d109b499..8ae96311026f33 100644
--- a/Doc/library/argparse.rst
+++ b/Doc/library/argparse.rst
@@ -1679,6 +1679,12 @@ The Namespace object
Simple class used by default by :meth:`~ArgumentParser.parse_args` to create
an object holding attributes and return it.
+ :class:`!Namespace` objects support :func:`copy.replace`,
+ which returns a copy of the object with the specified attributes replaced.
+
+ .. versionchanged:: next
+ Added support for :func:`copy.replace`.
+
This class is deliberately simple, just an :class:`object` subclass with a
readable string representation. If you prefer to have dict-like view of the
attributes, you can use the standard Python idiom, :func:`vars`::
diff --git a/Lib/argparse.py b/Lib/argparse.py
index 25994d7a389efa..fe9fde7f65830f 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -1545,6 +1545,12 @@ def __eq__(self, other):
def __contains__(self, key):
return key in self.__dict__
+ def __replace__(self, /, **changes):
+ new = self.__class__()
+ new.__dict__.update(self.__dict__)
+ new.__dict__.update(changes)
+ return new
+
class _ActionsContainer(object):
diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
index ae02cd11804e50..950671e4395cd4 100644
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -2,6 +2,7 @@
import _colorize
import contextlib
+import copy
import functools
import io
import operator
@@ -6267,6 +6268,19 @@ def test_equality_returns_notimplemented(self):
self.assertIs(ns.__eq__(None), NotImplemented)
self.assertIs(ns.__ne__(None), NotImplemented)
+ def test_replace(self):
+ ns = argparse.Namespace(a=1, b=2)
+ new = copy.replace(ns, b=3, c=4)
+ self.assertIsInstance(new, argparse.Namespace)
+ self.assertEqual(new, argparse.Namespace(a=1, b=3, c=4))
+ self.assertEqual(ns, argparse.Namespace(a=1, b=2))
+
+ class MyNamespace(argparse.Namespace):
+ pass
+ new = copy.replace(MyNamespace(a=1), a=2)
+ self.assertIsInstance(new, MyNamespace)
+ self.assertEqual(new.a, 2)
+
# ===================
# File encoding tests
diff --git
a/Misc/NEWS.d/next/Library/2026-08-01-19-04-00.gh-issue-155043.Ar1Nsp.rst
b/Misc/NEWS.d/next/Library/2026-08-01-19-04-00.gh-issue-155043.Ar1Nsp.rst
new file mode 100644
index 00000000000000..715b0a1783730e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-08-01-19-04-00.gh-issue-155043.Ar1Nsp.rst
@@ -0,0 +1 @@
+:class:`argparse.Namespace` objects now support :func:`copy.replace`.
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