https://github.com/python/cpython/commit/244300162d2e863a0588d1754e224d68931ada37
commit: 244300162d2e863a0588d1754e224d68931ada37
branch: main
author: Victor Stinner <[email protected]>
committer: vstinner <[email protected]>
date: 2026-05-20T13:22:57+02:00
summary:
gh-149807: Fix hash(frozendict): compute (key, value) pair hash (#149841)
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2026-05-14-19-41-03.gh-issue-149807.IwGaCo.rst
M Lib/test/test_dict.py
M Objects/dictobject.c
M Objects/tupleobject.c
diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index 4efb066d4fd01c..f26586809238f0 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -1903,10 +1903,35 @@ def test_hash(self):
self.assertEqual(hash(frozendict(x=1, y=2)),
hash(frozendict(y=2, x=1)))
+ # Check that hash() computes the hash of (key, value) pairs
+ cases = [
+ frozendict(a=False, b=True, c=True),
+ frozendict(a=True, b=False, c=True),
+ frozendict(a=True, b=True, c=False),
+ frozendict({False: "a", "b": True, "c": True}),
+ frozendict({"a": "b", False: True, True: "c"}),
+ ]
+ hashes = {hash(fd) for fd in cases}
+ self.assertEqual(len(hashes), len(cases))
+
fd = frozendict(x=[1], y=[2])
with self.assertRaisesRegex(TypeError, "unhashable type: 'list'"):
hash(fd)
+ @support.cpython_only
+ def test_hash_cpython(self):
+ # Check that hash(frozendict) implementation is:
+ # hash(frozenset(fd.items()))
+ for fd in (
+ frozendict(),
+ frozendict(x=1, y=2),
+ frozendict(y=2, x=1),
+ frozendict(a=False, b=True, c=True),
+ frozendict.fromkeys('abc'),
+ ):
+ with self.subTest(fd=fd):
+ self.assertEqual(hash(fd), hash(frozenset(fd.items())))
+
def test_fromkeys(self):
self.assertEqual(frozendict.fromkeys('abc'),
frozendict(a=None, b=None, c=None))
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2026-05-14-19-41-03.gh-issue-149807.IwGaCo.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2026-05-14-19-41-03.gh-issue-149807.IwGaCo.rst
new file mode 100644
index 00000000000000..a94c737e73619d
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2026-05-14-19-41-03.gh-issue-149807.IwGaCo.rst
@@ -0,0 +1,2 @@
+Fix ``hash(frozendict)``: compute the hash of each ``(key, value)`` pair
+correctly. Patch by Victor Stinner.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index a7d67812bec925..3830fedd42bd27 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -8230,6 +8230,39 @@ _shuffle_bits(Py_uhash_t h)
return ((h ^ 89869747UL) ^ (h << 16)) * 3644798167UL;
}
+// Compute hash((key, value)).
+// Code copied from tuple_hash().
+static Py_hash_t
+frozendict_pair_hash(Py_hash_t key_hash, PyObject *value)
+{
+ assert(key_hash != -1);
+
+ const Py_ssize_t len = 2;
+ Py_uhash_t acc = _PyTuple_HASH_XXPRIME_5;
+
+ Py_uhash_t lane = key_hash;
+ acc += lane * _PyTuple_HASH_XXPRIME_2;
+ acc = _PyTuple_HASH_XXROTATE(acc);
+ acc *= _PyTuple_HASH_XXPRIME_1;
+
+ lane = PyObject_Hash(value);
+ if (lane == (Py_uhash_t)-1) {
+ return -1;
+ }
+ acc += lane * _PyTuple_HASH_XXPRIME_2;
+ acc = _PyTuple_HASH_XXROTATE(acc);
+ acc *= _PyTuple_HASH_XXPRIME_1;
+
+ /* Add input length, mangled to keep the historical value of hash(()). */
+ acc += len ^ (_PyTuple_HASH_XXPRIME_5 ^ 3527539UL);
+
+ if (acc == (Py_uhash_t)-1) {
+ acc = 1546275796;
+ }
+ return acc;
+}
+
+
// Code copied from frozenset_hash()
static Py_hash_t
frozendict_hash(PyObject *op)
@@ -8243,20 +8276,15 @@ frozendict_hash(PyObject *op)
PyDictObject *mp = _PyAnyDict_CAST(op);
Py_uhash_t hash = 0;
- PyObject *key, *value; // borrowed refs
+ PyObject *value; // borrowed ref
Py_ssize_t pos = 0;
- while (PyDict_Next(op, &pos, &key, &value)) {
- Py_hash_t key_hash = PyObject_Hash(key);
- if (key_hash == -1) {
- return -1;
- }
- hash ^= _shuffle_bits(key_hash);
-
- Py_hash_t value_hash = PyObject_Hash(value);
- if (value_hash == -1) {
+ Py_hash_t key_hash;
+ while (_PyDict_Next(op, &pos, NULL, &value, &key_hash)) {
+ Py_hash_t pair_hash = frozendict_pair_hash(key_hash, value);
+ if (pair_hash == -1) {
return -1;
}
- hash ^= _shuffle_bits(value_hash);
+ hash ^= _shuffle_bits(pair_hash);
}
/* Factor in the number of active entries */
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 94230002427546..6120e70f3eeea4 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -363,6 +363,9 @@ tuple_repr(PyObject *self)
https://github.com/Cyan4973/xxHash/blob/master/doc/xxhash_spec.md
The constants for the hash function are defined in pycore_tuple.h.
+
+ If you update this code, update also frozendict_pair_hash() which copied
+ this code.
*/
static Py_hash_t
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