Jun 30, 2025 · Apr 22, 2025 · Apr 22, 2025 · Apr 22, 2025 · Apr 22, 2025 · Jun 18, 2025
diff --git a/Lib/test/test_free_threading/test_itertools_combinatoric.py b/Lib/test/test_free_threading/test_itertools_combinatoric.py
 import unittest
 from threading import Thread, Barrier
 from itertools import combinations, product
 from test.support import threading_helper


 threading_helper.requires_working_threading(module=True)

 def test_concurrent_iteration(iterator, number_of_threads):
    barrier = Barrier(number_of_threads)
    def iterator_worker(it):
        barrier.wait()
        while True:
            try:
                _ = next(it)
            except StopIteration:
                return

    worker_threads = []
    for ii in range(number_of_threads):
        worker_threads.append(
            Thread(target=iterator_worker, args=[iterator]))

    with threading_helper.start_threads(worker_threads):
        pass

    barrier.reset()

 class ItertoolsThreading(unittest.TestCase):

    @threading_helper.reap_threads
    def test_combinations(self):
        number_of_threads = 10
        number_of_iterations = 24

        for it in range(number_of_iterations):
            iterator = combinations((1, 2, 3, 4, 5), 2)
            test_concurrent_iteration(iterator, number_of_threads)

    @threading_helper.reap_threads
    def test_product(self):
        number_of_threads = 10
        number_of_iterations = 24

        for it in range(number_of_iterations):
            iterator = product((1, 2, 3, 4, 5), (10, 20, 30))
            test_concurrent_iteration(iterator, number_of_threads)


 if __name__ == "__main__":
    unittest.main()
diff --git a/Misc/NEWS.d/next/Library/2025-04-22-21-00-23.gh-issue-123471.asOLA2.rst b/Misc/NEWS.d/next/Library/2025-04-22-21-00-23.gh-issue-123471.asOLA2.rst
 Make concurrent iterations over :class:`itertools.combinations` and :class:`itertools.product` safe under free-threading.
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
 }

 static PyObject *
 product_next(PyObject *op)
 product_next_lock_held(PyObject *op)
 {
    productobject *lz = productobject_CAST(op);
    PyObject *pool;
    return NULL;
 }

 static PyObject *
 product_next(PyObject *op)
 {
    PyObject *result;
    Py_BEGIN_CRITICAL_SECTION(op);
    result = product_next_lock_held(op);
    Py_END_CRITICAL_SECTION()
    return result;
 }

 static PyMethodDef product_methods[] = {
    {"__sizeof__", product_sizeof, METH_NOARGS, sizeof_doc},
    {NULL,              NULL}   /* sentinel */
 }

 static PyObject *
 combinations_next(PyObject *op)
 combinations_next_lock_held(PyObject *op)
 {
    combinationsobject *co = combinationsobject_CAST(op);
    PyObject *elem;
    return NULL;
 }

 static PyObject *
 combinations_next(PyObject *op)
 {
    PyObject *result;
    Py_BEGIN_CRITICAL_SECTION(op);
    result = combinations_next_lock_held(op);
    Py_END_CRITICAL_SECTION()
    return result;
 }

 static PyMethodDef combinations_methods[] = {
    {"__sizeof__", combinations_sizeof, METH_NOARGS, sizeof_doc},
    {NULL,              NULL}   /* sentinel */
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,51 @@
		import unittest
		from threading import Thread, Barrier
		from itertools import combinations, product
		from test.support import threading_helper


		threading_helper.requires_working_threading(module=True)

		def test_concurrent_iteration(iterator, number_of_threads):
		barrier = Barrier(number_of_threads)
		def iterator_worker(it):
		barrier.wait()
		while True:
		try:
		_ = next(it)
		except StopIteration:
		return

		worker_threads = []
		for ii in range(number_of_threads):
		worker_threads.append(
		Thread(target=iterator_worker, args=[iterator]))

		with threading_helper.start_threads(worker_threads):
		pass

		barrier.reset()

		class ItertoolsThreading(unittest.TestCase):

		@threading_helper.reap_threads
		def test_combinations(self):
		number_of_threads = 10
		number_of_iterations = 24

		for it in range(number_of_iterations):
		iterator = combinations((1, 2, 3, 4, 5), 2)
		test_concurrent_iteration(iterator, number_of_threads)

		@threading_helper.reap_threads
		def test_product(self):
		number_of_threads = 10
		number_of_iterations = 24

		for it in range(number_of_iterations):
		iterator = product((1, 2, 3, 4, 5), (10, 20, 30))
		test_concurrent_iteration(iterator, number_of_threads)


		if __name__ == "__main__":
		unittest.main()
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Make concurrent iterations over :class:`itertools.combinations` and :class:`itertools.product` safe under free-threading.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2086,7 +2086,7 @@ product_traverse(PyObject op, visitproc visit, void arg)
		}

		static PyObject *
		product_next(PyObject *op)
		product_next_lock_held(PyObject *op)
		{
		productobject *lz = productobject_CAST(op);
		PyObject *pool;
Expand DownExpand Up		@@ -2172,6 +2172,16 @@ product_next(PyObject *op)
		return NULL;
		}

		static PyObject *
		product_next(PyObject *op)
		{
		PyObject *result;
		Py_BEGIN_CRITICAL_SECTION(op);
		result = product_next_lock_held(op);
		Py_END_CRITICAL_SECTION()
		return result;
		}

		static PyMethodDef product_methods[] = {
		{"__sizeof__", product_sizeof, METH_NOARGS, sizeof_doc},
		{NULL, NULL} /* sentinel */
Expand DownExpand Up		@@ -2319,7 +2329,7 @@ combinations_traverse(PyObject op, visitproc visit, void arg)
		}

		static PyObject *
		combinations_next(PyObject *op)
		combinations_next_lock_held(PyObject *op)
		{
		combinationsobject *co = combinationsobject_CAST(op);
		PyObject *elem;
Expand DownExpand Up		@@ -2404,6 +2414,16 @@ combinations_next(PyObject *op)
		return NULL;
		}

		static PyObject *
		combinations_next(PyObject *op)
		{
		PyObject *result;
		Py_BEGIN_CRITICAL_SECTION(op);
		result = combinations_next_lock_held(op);
		Py_END_CRITICAL_SECTION()
		return result;
		}

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