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gh-141510: Optimize {frozen}dict.fromkeys for frozendict #144915

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corona10 merged 18 commits into from
Feb 17, 2026
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gh-141510: Optimize {frozen}dict.fromkeys for frozendict #144915

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gh-141510: Optimize {frozen}dict.fromkeys for frozendict
corona10 Feb 17, 2026
36f2d77
Add NEWS.d
corona10 Feb 17, 2026
f056fa6
Update docs
corona10 Feb 17, 2026
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fix
corona10 Feb 17, 2026
a49d630
Address code review
corona10 Feb 17, 2026
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Address code review
corona10 Feb 17, 2026
49e8a98
Address code review
corona10 Feb 17, 2026
8d8fc98
Address code review
corona10 Feb 17, 2026
fa2505a
nit
corona10 Feb 17, 2026
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fix
corona10 Feb 17, 2026
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fix
corona10 Feb 17, 2026
305b2ef
fix
corona10 Feb 17, 2026
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Revert "fix"
corona10 Feb 17, 2026
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Revert "fix"
corona10 Feb 17, 2026
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corona10 Feb 17, 2026
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Revert "nit"
corona10 Feb 17, 2026
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Revert "Address code review"
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Address code review
corona10 Feb 17, 2026
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-02-17-22-27-11.gh-issue-141510.-4yYsf.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Optimize :meth:`!frozendict.fromkeys` to avoid unnecessary thread-safety operations
in frozendict cases. Patch by Donghee Na.
63 changes: 56 additions & 7 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2671,10 +2671,8 @@ _PyDict_LoadBuiltinsFromGlobals(PyObject *globals)

/* Consumes references to key and value */
static int
setitem_take2_lock_held(PyDictObject *mp, PyObject *key, PyObject *value)
anydict_setitem_take2(PyDictObject *mp, PyObject *key, PyObject *value)
{
ASSERT_DICT_LOCKED(mp);

assert(key);
assert(value);
assert(PyAnyDict_Check(mp));
Expand All @@ -2693,6 +2691,14 @@ setitem_take2_lock_held(PyDictObject *mp, PyObject *key, PyObject *value)
return insertdict(mp, key, hash, value);
}

/* Consumes references to key and value */
static int
setitem_take2_lock_held(PyDictObject *mp, PyObject *key, PyObject *value)
{
ASSERT_DICT_LOCKED(mp);
return anydict_setitem_take2(mp, key, value);
}

int
_PyDict_SetItem_Take2(PyDictObject *mp, PyObject *key, PyObject *value)
{
Expand Down Expand Up @@ -3284,15 +3290,23 @@ _PyDict_FromKeys(PyObject *cls, PyObject *iterable, PyObject *value)
return NULL;


if (PyAnyDict_CheckExact(d)) {
if (PyAnyDict_CheckExact(iterable)) {
if (PyDict_CheckExact(d)) {
if (PyDict_CheckExact(iterable)) {
PyDictObject *mp = (PyDictObject *)d;

Py_BEGIN_CRITICAL_SECTION2(d, iterable);
d = (PyObject *)dict_dict_fromkeys(mp, iterable, value);
Py_END_CRITICAL_SECTION2();
return d;
}
else if (PyFrozenDict_CheckExact(iterable)) {
PyDictObject *mp = (PyDictObject *)d;

Py_BEGIN_CRITICAL_SECTION(d);
d = (PyObject *)dict_dict_fromkeys(mp, iterable, value);
Py_END_CRITICAL_SECTION();
return d;
}
else if (PyAnySet_CheckExact(iterable)) {
PyDictObject *mp = (PyDictObject *)d;

Expand All @@ -3302,14 +3316,37 @@ _PyDict_FromKeys(PyObject *cls, PyObject *iterable, PyObject *value)
return d;
}
}
else if (PyFrozenDict_CheckExact(d)) {
if (PyDict_CheckExact(iterable)) {
PyDictObject *mp = (PyDictObject *)d;

Py_BEGIN_CRITICAL_SECTION(iterable);
d = (PyObject *)dict_dict_fromkeys(mp, iterable, value);
Py_END_CRITICAL_SECTION();
return d;
}
else if (PyFrozenDict_CheckExact(iterable)) {
PyDictObject *mp = (PyDictObject *)d;
d = (PyObject *)dict_dict_fromkeys(mp, iterable, value);
return d;
}
else if (PyAnySet_CheckExact(iterable)) {
PyDictObject *mp = (PyDictObject *)d;

Py_BEGIN_CRITICAL_SECTION(iterable);
d = (PyObject *)dict_set_fromkeys(mp, iterable, value);
Py_END_CRITICAL_SECTION();
return d;
}
}

it = PyObject_GetIter(iterable);
if (it == NULL){
Py_DECREF(d);
return NULL;
}

if (PyAnyDict_CheckExact(d)) {
if (PyDict_CheckExact(d)) {
Py_BEGIN_CRITICAL_SECTION(d);
while ((key = PyIter_Next(it)) != NULL) {
status = setitem_lock_held((PyDictObject *)d, key, value);
Expand All @@ -3321,7 +3358,19 @@ _PyDict_FromKeys(PyObject *cls, PyObject *iterable, PyObject *value)
}
dict_iter_exit:;
Py_END_CRITICAL_SECTION();
} else {
}
else if (PyFrozenDict_CheckExact(d)) {
while ((key = PyIter_Next(it)) != NULL) {
// anydict_setitem_take2 consumes a reference to key
status = anydict_setitem_take2((PyDictObject *)d,
key, Py_NewRef(value));
if (status < 0) {
assert(PyErr_Occurred());
goto Fail;
}
}
}
else {
while ((key = PyIter_Next(it)) != NULL) {
status = PyObject_SetItem(d, key, value);
Py_DECREF(key);
Expand Down
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