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gh-155324: Pickle frozendict with all protocols #155325

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gh-155324: Pickle frozendict with all protocols #155325

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21 changes: 8 additions & 13 deletions Lib/test/test_dict.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1991,19 +1991,14 @@ def test_pickle(self):
if type(fd) == FrozenDictSlots:
fd.slot_attr = 456
with self.subTest(fd=fd, proto=proto):
if proto >= 2:
p = pickle.dumps(fd, proto)
fd2 = pickle.loads(p)
self.assertEqual(fd2, fd)
self.assertEqual(type(fd2), type(fd))
if type(fd) == FrozenDict:
self.assertEqual(fd2.attr, 123)
if type(fd) == FrozenDictSlots:
self.assertEqual(fd2.slot_attr, 456)
else:
# protocol 0 and 1 don't support frozendict
with self.assertRaises(TypeError):
pickle.dumps(fd, proto)
p = pickle.dumps(fd, proto)
fd2 = pickle.loads(p)
self.assertEqual(fd2, fd)
self.assertEqual(type(fd2), type(fd))
if type(fd) == FrozenDict:
self.assertEqual(fd2.attr, 123)
if type(fd) == FrozenDictSlots:
self.assertEqual(fd2.slot_attr, 456)

def test_pickle_iter(self):
fd = frozendict(c=1, b=2, a=3, d=4, e=5, f=6)
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-08-07-18-19-51.gh-issue-155324.Pk4Rz7.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
``frozendict`` can now be pickled with all pickle protocols, matching
:class:`frozenset`. Previously protocols 0 and 1 raised :exc:`TypeError`.
Patch by tonghuaroot.
24 changes: 20 additions & 4 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8344,14 +8344,29 @@ _PyObject_InlineValuesConsistencyCheck(PyObject *obj)
// --- frozendict implementation ---------------------------------------------

static PyObject *
frozendict_getnewargs(PyObject *op, PyObject *Py_UNUSED(dummy))
frozendict_reduce(PyObject *op, PyObject *Py_UNUSED(dummy))
{
// Call dict(op): convert 'op' frozendict to a dict
// Mirror frozenset.__reduce__ so frozendict pickles at every protocol
// (__getnewargs__ alone only works at protocol 2 and above).
// Call dict(op) to convert the frozendict to a dict argument.
PyObject *arg = PyObject_CallOneArg((PyObject*)&PyDict_Type, op);
if (arg == NULL) {
return NULL;
}
return Py_BuildValue("(N)", arg);
PyObject *args = PyTuple_Pack(1, arg);
Py_DECREF(arg);
if (args == NULL) {
return NULL;
}
PyObject *state = _PyObject_GetState(op);
if (state == NULL) {
Py_DECREF(args);
return NULL;
}
PyObject *result = PyTuple_Pack(3, Py_TYPE(op), args, state);
Py_DECREF(args);
Py_DECREF(state);
return result;
}


Expand All @@ -8377,7 +8392,8 @@ static PyMethodDef frozendict_methods[] = {
DICT___REVERSED___METHODDEF
{"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS,
PyDoc_STR("frozendicts are generic over two types, signifying (respectively) the types of the frozendict's keys and values")},
{"__getnewargs__", frozendict_getnewargs, METH_NOARGS},
{"__reduce__", frozendict_reduce, METH_NOARGS,
PyDoc_STR("Return state information for pickling.")},
{NULL, NULL} /* sentinel */
};

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