from bitstring import Bits, pack

bits = pack('uint:5, uint:1, uint:10, uint:8', 2, 0, 64, 2)

byte1, byte2, byte3 = bits.unpack('bytes:1,bytes:1,bytes:1')

listOfBytes = [byte1, byte2, byte3]

checksum  = sum(map(ord, listOfBytes))

if checksum > 511:
    checksum = checksum - 512
if checksum > 255:
    checksum = checksum - 256
if checksum > 127:
    checksum = checksum - 128

bits = pack('uint:5, uint:1, uint:10, uint:8, uint:8', 2, 0, 64, 2, checksum)