gh-131540: Improve type checking error for args in threading.Thread objects

Lib/test/test_threading.py

@@ -174,11 +174,33 @@ def test_args_argument(self):
                 t.start()
                 t.join()
 
-    def test_lock_no_args(self):
-        threading.Lock()  # works
-        self.assertRaises(TypeError, threading.Lock, 1)
-        self.assertRaises(TypeError, threading.Lock, a=1)
-        self.assertRaises(TypeError, threading.Lock, 1, 2, a=1, b=2)
+    def test_args_invalid_arguments_raises_typeerror(self):
+        def task(x):
+            pass
+
+        invalid_args = (
+            1,
+            3.14,
+            None,
+            object(),
+        )
+
+        for args in invalid_args:
+            with self.subTest(args=args):
+                with self.assertRaises(TypeError):
+                    threading.Thread(target=task, args=args)
+
+    def test_args_valid_inputs_does_not_raise(self):
+        def task():
+            pass
+
+        class CustomIter:
+            def __iter__(self):
+                yield
+        try:
+            t = threading.Thread(target=task, args=CustomIter())
+        except TypeError as e:
+            self.fail(f"Thread raised an exception with an object that has the '__iter__' attribute with error {e}")
 
     def test_lock_no_subclass(self):
         # Intentionally disallow subclasses of threading.Lock because they have

Lib/threading.py

@@ -909,6 +909,8 @@ class is implemented.
 
         self._target = target
         self._name = name
+        if not hasattr(args, '__iter__'):
+            raise TypeError(f"'args' must be a iterable like a tuple or list, not {type(args).__name__}")
         self._args = args
         self._kwargs = kwargs
         if daemon is not None:

Misc/NEWS.d/next/Library/2025-03-22-17-20-31.gh-issue-131540.1mRP-a.rst

@@ -0,0 +1,2 @@
+threading.Thread now validates that 'args' is iterable. Raises TypeError if it is not.
+