python · kumaraditya303 · Mar 12, 2025 · Jan 15, 2025 · Jan 28, 2025 · Feb 19, 2025
@@ -0,0 +1,39 @@
+import unittest
+import sys
+from threading import Thread, Barrier
+from itertools import batched
+from test.support import threading_helper
+
+
+threading_helper.requires_working_threading(module=True)
+
+class EnumerateThreading(unittest.TestCase):
+
+    @threading_helper.reap_threads
+    def test_threading(self):
+        number_of_threads = 10
+        number_of_iterations = 20
+        barrier = Barrier(number_of_threads)
+        def work(it):
+            barrier.wait()
+            while True:
+                try:
+                    _ = next(it)
+                except StopIteration:
+                    break
+
+        data = tuple(range(1000))
+        for it in range(number_of_iterations):
+            batch_iterator = batched(data, 2)
+            worker_threads = []
+            for ii in range(number_of_threads):
+                worker_threads.append(
+                    Thread(target=work, args=[batch_iterator]))
+
+            with threading_helper.start_threads(worker_threads):
+                pass
+
+            barrier.reset()
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Misc/NEWS.d/next/Library/2025-02-19-08-06-37.gh-issue-123471.br7uyR.rst b/Misc/NEWS.d/next/Library/2025-02-19-08-06-37.gh-issue-123471.br7uyR.rst
@@ -0,0 +1 @@
+Make concurrent iterations over :class:`itertools.batched` safe under free-threading.
@@ -191,12 +191,12 @@ batched_next(PyObject *op)
 {
    batchedobject *bo = batchedobject_CAST(op);
    Py_ssize_t i;
-    Py_ssize_t n = bo->batch_size;
+    Py_ssize_t n = FT_ATOMIC_LOAD_SSIZE_RELAXED(bo->batch_size);
    PyObject *it = bo->it;
    PyObject *item;
    PyObject *result;

-    if (it == NULL) {
+    if (n < 0) {
        return NULL;
    }
    result = PyTuple_New(n);
@@ -218,19 +218,28 @@ batched_next(PyObject *op)
    if (PyErr_Occurred()) {
        if (!PyErr_ExceptionMatches(PyExc_StopIteration)) {
            /* Input raised an exception other than StopIteration */
+            FT_ATOMIC_STORE_SSIZE_RELAXED(bo->batch_size, -1);
+#ifndef Py_GIL_DISABLED
            Py_CLEAR(bo->it);
+#endif
            Py_DECREF(result);
            return NULL;
        }
        PyErr_Clear();
    }
    if (i == 0) {
+        FT_ATOMIC_STORE_SSIZE_RELAXED(bo->batch_size, -1);
+#ifndef Py_GIL_DISABLED
        Py_CLEAR(bo->it);
+#endif
        Py_DECREF(result);
        return NULL;
    }
    if (bo->strict) {
+        FT_ATOMIC_STORE_SSIZE_RELAXED(bo->batch_size, -1);
+#ifndef Py_GIL_DISABLED
        Py_CLEAR(bo->it);
+#endif
        Py_DECREF(result);
        PyErr_SetString(PyExc_ValueError, "batched(): incomplete batch");
        return NULL;
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Make concurrent iterations over :class:`itertools.batched` safe under free-threading.