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>

Lib/test/test_threading.py

@@ -123,6 +123,32 @@ class ThreadTests(BaseTestCase):
             thread = threading.Thread(target=func)
             self.assertEqual(thread.name, "Thread-5 (func)")
 
+    def test_args_argument(self):
+        # bpo-45735: Using list or tuple as *args* in constructor could
+        # achieve the same effect.
+        num_list = [1]
+        num_tuple = (1,)
+
+        str_list = ["str"]
+        str_tuple = ("str",)
+
+        list_in_tuple = ([1],)
+        tuple_in_list = [(1,)]
+
+        test_cases = (
+            (num_list, lambda arg: self.assertEqual(arg, 1)),
+            (num_tuple, lambda arg: self.assertEqual(arg, 1)),
+            (str_list, lambda arg: self.assertEqual(arg, "str")),
+            (str_tuple, lambda arg: self.assertEqual(arg, "str")),
+            (list_in_tuple, lambda arg: self.assertEqual(arg, [1])),
+            (tuple_in_list, lambda arg: self.assertEqual(arg, (1,)))
+        )
+
+        for args, target in test_cases:
+            with self.subTest(target=target, args=args):
+                t = threading.Thread(target=target, args=args)
+                t.start()
+
     @cpython_only
     def test_disallow_instantiation(self):
         # Ensure that the type disallows instantiation (bpo-43916)