gh-136470: Correct InterpreterPoolExecutor's default thread name

Lib/concurrent/futures/interpreter.py

@@ -118,5 +118,7 @@ def __init__(self, max_workers=None, thread_name_prefix='',
                 each worker interpreter.
             initargs: A tuple of arguments to pass to the initializer.
         """
+        thread_name_prefix = (thread_name_prefix or
+                              (f"InterpreterPoolExecutor-{self._counter()}"))
         super().__init__(max_workers, thread_name_prefix,
                          initializer, initargs)

Lib/test/test_concurrent_futures/test_interpreter_pool.py

@@ -1,3 +1,4 @@
+import _thread
 import asyncio
 import contextlib
 import io
@@ -498,6 +499,20 @@ def test_import_interpreter_pool_executor(self):
         self.assertEqual(p.stdout.decode(), '')
         self.assertEqual(p.stderr.decode(), '')
 
+    def test_thread_name_prefix(self):
+        self.assertStartsWith(self.executor._thread_name_prefix,
+                              "InterpreterPoolExecutor-")
+
+    @unittest.skipUnless(hasattr(_thread, '_get_name'), "missing _thread._get_name")
+    def test_thread_name_prefix_with_thread_get_name(self):
+        def get_thread_name():
+            import _thread
+            return _thread._get_name()
+
+        # Some platforms (Linux) are using 16 bytes to store the thread name,
+        # so only compare the first 15 bytes (without the trailing \n).
+        self.assertStartsWith(self.executor.submit(get_thread_name).result(),
+                              "InterpreterPoolExecutor-"[:15])
 
 class AsyncioTest(InterpretersMixin, testasyncio_utils.TestCase):
 

Misc/NEWS.d/next/Library/2025-07-10-00-47-37.gh-issue-136470.KlUEUG.rst

@@ -0,0 +1,2 @@
+Correct :class:`concurrent.futures.InterpreterPoolExecutor`'s default thread
+name.