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gh-123471: Make concurrent iteration over itertools.permutations and itertools.combinations_with_replacement thread-safe #144402

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Merged
colesbury merged 8 commits into from
Feb 4, 2026
Merged

gh-123471: Make concurrent iteration over itertools.permutations and itertools.combinations_with_replacement thread-safe #144402

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56b615e
Make itertools.combinations_with_replacement thread-safe
eendebakpt Feb 2, 2026
8139046
Make itertools.combinations_with_replacement thread-safe
eendebakpt Feb 2, 2026
6370bc4
Make permutations thread-safe
eendebakpt Feb 2, 2026
af909ce
remove redundant variable
eendebakpt Feb 2, 2026
dbb33bd
refactor code based on review
eendebakpt Feb 3, 2026
498f314
📜🤖 Added by blurb_it.
blurb-it[bot] Feb 3, 2026
c790b21
Apply suggestion from @eendebakpt
eendebakpt Feb 3, 2026
85540d3
Merge branch 'main' into cwr_ft
eendebakpt Feb 3, 2026
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Make permutations thread-safe
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@eendebakpt
eendebakpt committed Feb 2, 2026
commit 6370bc44b957c587d83a0fd31f1881683f487455
31 changes: 29 additions & 2 deletions Lib/test/test_free_threading/test_itertools.py
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
import unittest
from threading import Thread, Barrier
from itertools import batched, chain, combinations_with_replacement, cycle
from itertools import batched, chain, combinations_with_replacement, cycle, permutations
from test.support import threading_helper


Expand Down Expand Up @@ -92,7 +92,7 @@ def work(it):
@threading_helper.reap_threads
def test_combinations_with_replacement(self):
number_of_threads = 6
number_of_iterations = 50
number_of_iterations = 36
data = tuple(range(2))

barrier = Barrier(number_of_threads)
Expand All @@ -116,6 +116,33 @@ def work(it):

barrier.reset()

@threading_helper.reap_threads
def test_permutations(self):
number_of_threads = 6
number_of_iterations = 36
data = tuple(range(4))

barrier = Barrier(number_of_threads)
def work(it):
barrier.wait()
while True:
try:
next(it)
except StopIteration:
break

for _ in range(number_of_iterations):
perm_iterator = permutations(data, 2)
worker_threads = []
for _ in range(number_of_threads):
worker_threads.append(
Thread(target=work, args=[perm_iterator]))

with threading_helper.start_threads(worker_threads):
pass

barrier.reset()


if __name__ == "__main__":
unittest.main()
12 changes: 11 additions & 1 deletion Modules/itertoolsmodule.c
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Expand Up @@ -2856,7 +2856,7 @@ permutations_traverse(PyObject *op, visitproc visit, void *arg)
}

static PyObject *
permutations_next(PyObject *op)
permutations_next_lock_held(PyObject *op)
{
permutationsobject *po = permutationsobject_CAST(op);
PyObject *elem;
Expand Down Expand Up @@ -2946,6 +2946,16 @@ permutations_next(PyObject *op)
return NULL;
}

static PyObject *
permutations_next(PyObject *op)
{
PyObject *result;
Py_BEGIN_CRITICAL_SECTION(op);
result = permutations_next_lock_held(op);
Py_END_CRITICAL_SECTION()
return result;
}

static PyMethodDef permuations_methods[] = {
{"__sizeof__", permutations_sizeof, METH_NOARGS, sizeof_doc},
{NULL, NULL} /* sentinel */
Expand Down
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