Calculate checksum from the data part of an NMEA sentence

nmea_checksum.py

import sys
import operator

# Given the data part of an NMEA sentence (Remove the $, remove the * onwards, keep the last comma)
# calculates the checksum

def checksum_calculate(nmeadata):
    csum = 0
    for c in nmeadata:
       csum ^= ord(c)
    return csum



if __name__=='__main__':
    nmeadata=sys.argv[1] if len(sys.argv)>1 else "GPGGA,174134.000,4345.9112,N,09643.8029,W,1,05,2.7,452.6,M,-27.1,M,,0000"
    checksum=checksum_calculate(nmeadata)
    print("$" + nmeadata + "*" + format(checksum,'x').zfill(2).upper())
    print(hex(checksum))