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

Lib/test/test_threading.py

@@ -174,6 +174,21 @@ def test_args_argument(self):
                 t.start()
                 t.join()
 
+    def test_args_invalid_arguments_raises_typeerror(self):
+        def task(x):
+            pass
+
+        invalid_args = (
+            "test string",
+            1,
+            b"Bytes"
+        )
+
+        for args in invalid_args:
+            with self.subTest(args=args):
+                with self.assertRaises(TypeError):
+                    threading.Thread(target=task, args=args)
+
     def test_lock_no_args(self):
         threading.Lock()  # works
         self.assertRaises(TypeError, threading.Lock, 1)

Lib/threading.py

@@ -909,6 +909,8 @@ class is implemented.
 
         self._target = target
         self._name = name
+        if isinstance(args, (str, bytes)) or not hasattr(args, '__iter__'):
+            raise TypeError(f"'args' must be a non-string 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 @@
+Added validation in threading.Thread to ensure that 'args' is a tuple or list. Raises TypeError if a string, bytes, or non-iterable is passed.