python · hugovk · Mar 31, 2026 · Mar 6, 2026 · Mar 21, 2026 · Mar 21, 2026
diff --git a/Doc/library/plistlib.rst b/Doc/library/plistlib.rst
@@ -18,7 +18,7 @@ and XML plist files.

 The property list (``.plist``) file format is a simple serialization supporting
 basic object types, like dictionaries, lists, numbers and strings.  Usually the
-top level object is a dictionary.
+top level object is a dictionary or a frozen dictionary.

 To write out and to parse a plist file, use the :func:`dump` and
 :func:`load` functions.

@@ -213,7 +213,8 @@ For example::

 The following standard library modules have been updated to accept
 :class:`!frozendict`: :mod:`copy`, :mod:`decimal`, :mod:`json`, :mod:`marshal`,
-:mod:`pickle`, :mod:`pprint` and :mod:`xml.etree.ElementTree`.
+:mod:`plistlib` (only for serialization), :mod:`pickle`, :mod:`pprint` and
+:mod:`xml.etree.ElementTree`.

 :func:`eval` and :func:`exec` accept :class:`!frozendict` for *globals*, and
 :func:`type` and :meth:`str.maketrans` accept :class:`!frozendict` for *dict*.

diff --git a/Lib/plistlib.py b/Lib/plistlib.py
@@ -2,7 +2,7 @@

 The property list (.plist) file format is a simple XML pickle supporting
 basic object types, like dictionaries, lists, numbers and strings.
-Usually the top level object is a dictionary.
+Usually the top level object is a dictionary or a frozen dictionary.

 To write out a plist file, use the dump(value, file)
 function. 'value' is the top level object, 'file' is
@@ -357,7 +357,7 @@ def write_value(self, value):
        elif isinstance(value, float):
            self.simple_element("real", repr(value))

-        elif isinstance(value, dict):
+        elif isinstance(value, (dict, frozendict)):
            self.write_dict(value)

        elif isinstance(value, (bytes, bytearray)):
@@ -715,7 +715,7 @@ def _flatten(self, value):
            self._objidtable[id(value)] = refnum

        # And finally recurse into containers
-        if isinstance(value, dict):
+        if isinstance(value, (dict, frozendict)):
            keys = []
            values = []
            items = value.items()
@@ -836,7 +836,7 @@ def _write_object(self, value):
            self._write_size(0xA0, s)
            self._fp.write(struct.pack('>' + self._ref_format * s, *refs))

-        elif isinstance(value, dict):
+        elif isinstance(value, (dict, frozendict)):
            keyRefs, valRefs = [], []

            if self._sort_keys:
@@ -869,18 +869,18 @@ def _is_fmt_binary(header):
 # Generic bits
 #

-_FORMATS={
-    FMT_XML: dict(
+_FORMATS=frozendict({
+    FMT_XML: frozendict(
        detect=_is_fmt_xml,
        parser=_PlistParser,
        writer=_PlistWriter,
    ),
-    FMT_BINARY: dict(
+    FMT_BINARY: frozendict(
        detect=_is_fmt_binary,
        parser=_BinaryPlistParser,
        writer=_BinaryPlistWriter,
    )
-}
+})


 def load(fp, *, fmt=None, dict_type=dict, aware_datetime=False):

diff --git a/Lib/test/test_plistlib.py b/Lib/test/test_plistlib.py
@@ -792,6 +792,25 @@ def test_dict_members(self):
                })
                self.assertIsNot(pl2['first'], pl2['second'])

+    def test_frozendict(self):
+        pl = frozendict(
+            aString="Doodah",
+            anInt=728,
+            aDict=frozendict(
+                anotherString="hello",
+                aTrueValue=True,
+            ),
+            aList=["A", "B", 12],
+        )
+
+        for fmt in ALL_FORMATS:
+            with self.subTest(fmt=fmt):
+                data = plistlib.dumps(pl, fmt=fmt)
+                pl2 = plistlib.loads(data)
+                self.assertEqual(pl2, dict(pl))
+                self.assertIsInstance(pl2, dict)
+                self.assertIsInstance(pl2['aDict'], dict)
+
    def test_controlcharacters(self):
        for i in range(128):
            c = chr(i)

diff --git a/Misc/NEWS.d/next/Library/2026-03-21-16-03-16.gh-issue-141510.tKptA7.rst b/Misc/NEWS.d/next/Library/2026-03-21-16-03-16.gh-issue-141510.tKptA7.rst
@@ -0,0 +1,2 @@
+Support :class:`frozendict` in :mod:`plistlib`, for serialization only.
+Patch by Hugo van Kemenade.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Support :class:`frozendict` in :mod:`plistlib`, for serialization only.
		Patch by Hugo van Kemenade.