# HG changeset patch
# User Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
# Date 1346590759 -7200
# Branch 2.7
# Node ID 8f5d181194c5135827e896825aea43819c4af4eb
# Parent  2370e331241b51565be2a2d20cf2bf7bccf19f1c
Fix bug with argparse.Parser.parse_args(*args)

diff --git a/Lib/argparse.py b/Lib/argparse.py
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -1692,9 +1692,12 @@
         return args
 
     def parse_known_args(self, args=None, namespace=None):
-        # args default to the system args
         if args is None:
+            # args default to the system args
             args = _sys.argv[1:]
+        else:
+            # make sure that args are mutable
+            args = list(args)
 
         # default Namespace built from parser defaults
         if namespace is None:
diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -4486,6 +4486,24 @@
 
 class TestParseKnownArgs(TestCase):
 
+    def test_arguments_tuple(self):
+        parser = argparse.ArgumentParser()
+        parser.parse_args(())
+
+    def test_arguments_list(self):
+        parser = argparse.ArgumentParser()
+        parser.parse_args([])
+
+    def test_arguments_tuple_positional(self):
+        parser = argparse.ArgumentParser()
+        parser.add_argument('x')
+        parser.parse_args(('x',))
+
+    def test_arguments_list_positional(self):
+        parser = argparse.ArgumentParser()
+        parser.add_argument('x')
+        parser.parse_args(['x'])
+
     def test_optionals(self):
         parser = argparse.ArgumentParser()
         parser.add_argument('--foo')