# HG changeset patch
# Parent cdc3837cb1fcfc4273b46e84c533ec7e91246b71
Issue 16349: Bytes strings are allowed as struct format strings

diff -r cdc3837cb1fc Doc/library/struct.rst
--- a/Doc/library/struct.rst	Tue Dec 16 03:21:54 2014 -0500
+++ b/Doc/library/struct.rst	Thu Dec 18 05:45:37 2014 +0000
@@ -100,7 +100,8 @@
 Format strings are the mechanism used to specify the expected layout when
 packing and unpacking data.  They are built up from :ref:`format-characters`,
 which specify the type of data being packed/unpacked.  In addition, there are
-special characters for controlling the :ref:`struct-alignment`.
+special characters for controlling the :ref:`struct-alignment`.  They are
+normally character strings, but ASCII byte strings are also acceptable.
 
 
 .. _struct-alignment:
diff -r cdc3837cb1fc Lib/test/test_struct.py
--- a/Lib/test/test_struct.py	Tue Dec 16 03:21:54 2014 -0500
+++ b/Lib/test/test_struct.py	Thu Dec 18 05:45:37 2014 +0000
@@ -590,6 +590,11 @@
         self.check_sizeof('0s', 1)
         self.check_sizeof('0c', 0)
 
+    def test_bytes_format(self):
+        """Make sure bytes strings are accepted as format strings"""
+        self.assertEqual(b"\x00", struct.Struct(b"x").pack())
+        self.assertEqual(b"\x00", struct.pack(b"x"))
+
 
 class UnpackIteratorTest(unittest.TestCase):
     """