python · serhiy-storchaka · Mar 30, 2026 · Mar 26, 2026
@@ -1216,14 +1216,14 @@ def __repr__(self):
    def __or__(self, other):
        if isinstance(other, UserDict):
            return self.__class__(self.data | other.data)
-        if isinstance(other, dict):
+        if isinstance(other, (dict, frozendict)):
            return self.__class__(self.data | other)
        return NotImplemented

    def __ror__(self, other):
        if isinstance(other, UserDict):
            return self.__class__(other.data | self.data)
-        if isinstance(other, dict):
+        if isinstance(other, (dict, frozendict)):
            return self.__class__(other | self.data)
        return NotImplemented


diff --git a/Lib/test/test_userdict.py b/Lib/test/test_userdict.py
@@ -245,7 +245,7 @@ class G(collections.UserDict):
    test_repr_deep = mapping_tests.TestHashMappingProtocol.test_repr_deep

    def test_mixed_or(self):
-        for t in UserDict, dict, types.MappingProxyType:
+        for t in UserDict, dict, frozendict, types.MappingProxyType:
            with self.subTest(t.__name__):
                u = UserDict({0: 'a', 1: 'b'}) | t({1: 'c', 2: 'd'})
                self.assertEqual(u, {0: 'a', 1: 'c', 2: 'd'})
@@ -276,7 +276,7 @@ def test_mixed_or(self):
        self.assertIs(type(u), UserDictSubclass)

    def test_mixed_ior(self):
-        for t in UserDict, dict, types.MappingProxyType:
+        for t in UserDict, dict, frozendict, types.MappingProxyType:
            with self.subTest(t.__name__):
                u = u2 = UserDict({0: 'a', 1: 'b'})
                u |= t({1: 'c', 2: 'd'})

diff --git a/Misc/NEWS.d/next/Library/2026-03-26-14-44-07.gh-issue-145056.L9KPC3.rst b/Misc/NEWS.d/next/Library/2026-03-26-14-44-07.gh-issue-145056.L9KPC3.rst
@@ -0,0 +1 @@
+Add support for merging :class:`collections.UserDict` and :class:`frozendict`.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Add support for merging :class:`collections.UserDict` and :class:`frozendict`.