bpo-45735: Promise the long-time truth that `args=list` works (GH-30982)

For threads, and for multiprocessing, it's always been the case that ``args=list`` works fine when passed to ``Process()`` or ``Thread()``, and such code is common in the wild. But, according to the docs, only a tuple can be used. This brings the docs into synch with reality.

Doc changes by Charlie Zhao.
Co-authored-by: Tim Peters <tim.peters@gmail.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index b2d656ab428..6b1b1677910 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -247,6 +247,30 @@ class _TestProcess(BaseTestCase):
         self.assertEqual(current.ident, os.getpid())
         self.assertEqual(current.exitcode, None)
 
+    def test_args_argument(self):
+        # bpo-45735: Using list or tuple as *args* in constructor could
+        # achieve the same effect.
+        args_cases = (1, "str", [1], (1,))
+        args_types = (list, tuple)
+
+        test_cases = itertools.product(args_cases, args_types)
+
+        for args, args_type in test_cases:
+            with self.subTest(args=args, args_type=args_type):
+                q = self.Queue(1)
+                # pass a tuple or list as args
+                p = self.Process(target=self._test_args, args=args_type((q, args)))
+                p.daemon = True
+                p.start()
+                child_args = q.get()
+                self.assertEqual(child_args, args)
+                p.join()
+                close_queue(q)
+
+    @classmethod
+    def _test_args(cls, q, arg):
+        q.put(arg)
+
     def test_daemon_argument(self):
         if self.TYPE == "threads":
             self.skipTest('test not appropriate for {}'.format(self.TYPE))