diff -r 424d1e37c3d2 Lib/urllib/request.py
--- a/Lib/urllib/request.py     Tue Feb 01 02:12:30 2011 +0800
+++ b/Lib/urllib/request.py     Tue Feb 01 03:30:17 2011 +0800
@@ -1054,7 +1054,10 @@
                     'application/x-www-form-urlencoded')
             if not request.has_header('Content-length'):
                 try:
-                    mv = memoryview(data)
+                    if isinstance(data, str):
+                        mv = memoryview(bytes(data, 'ascii'))
+                    else:
+                        mv = memoryview(data)
                 except TypeError:
                     if isinstance(data, collections.Iterable):
                         raise ValueError("Content-Length should be specified \