Is this working as expected? >>> open( 'test', 'w' ).write( buffer( 'abcd', 2 ) ) >>> from cStringIO import StringIO >>> StringIO().write( buffer( 'abcd', 2 ) ) Traceback (innermost last): File "<pyshell#4>", line 1, in ? StringIO().write( buffer( 'abcd', 2 ) ) SystemError: bad argument to internal function >>> -- Best regards, Niki Spahiev