import struct import ctypes mm = struct.pack("hhl", 1, 2, 3) #mm = struct.pack("hhl01", 1,2,3) //padding nn = struct.unpack('hhl', mm) print mm, nn mm = struct.calcsize('ci') nn = struct.calcsize('ic') print mm, nn mm = ctypes.create_string_buffer(100) struct.pack_into('hhl', mm, 0, 1, 2, 3) print struct.unpack_from('hhl', mm, 0)