AEMO NMI checksum calculator

aemo_nmi_checksum.py

from itertools import chain

# Calculates the AEMO NMI checksum according to:
#
#    https://www.aemo.com.au/Electricity/National-Electricity-Market-NEM/Retail-and-metering/-/media/EBA9363B984841079712B3AAD374A859.ashx
#
# Always calculates the checksum with the 10 left-most digits if supplied with
# a 10 or 11 character string. Unspecified results occur for inputs of other lengths.
# 

def generate(nmi):
    if len(nmi) > 10:
        nmi=nmi[0:10]
    
    ascii = chain(map(lambda x : ord(x)*2, nmi[-1::-2]), map(lambda x : ord(x), nmi[-2::-2]))
    ascii_digits=''.join(map(lambda x: str(x), ascii))
    digits = map(lambda x : ord(x) - ord('0'), ascii_digits)
    reduction = sum(digits)
    return nmi+str(((10-(reduction % 10))%10))