nric-cert.py

nric-cert.py

# nric-cert.py
# verifies a Singaporean NRIC
# motivated by video from The Fun Social - How did your NRIC
# number come about?
# date created: June 15, 2017
# author: Nicky Lim

import sys

assert len(sys.argv) == 2, "Usage: python nric-cert.py <NRIC>"

nric = sys.argv[1].lower()

prefix = nric[0]
digits = [int(c) for c in nric[1:-1]] # represented as list of ints
suffix = nric[-1]

assert len(prefix) == 1 \
       and len(digits) == 7 \
       and len(suffix) == 1, "invalid length"

assert prefix in ['s','t','f','g'], "invalid prefix"

# for 's'-prefix holders, matches age from 1968 and above, else starts with
# 0 or 1
if (prefix == 's'):
    age = digits[0]*10 + digits[1]
    fd = int(digits[0]) # first digit
    assert (68 <= age and age <= 99) \
           or fd == 0 or fd == 1, "invalid age"

# verify digits
weights = [2,7,6,5,4,3,2]

total = sum([a*b for a,b in zip(digits,weights)])

if (prefix in ['t','g']):
    total += 4
    calc_suffix = ['x','w','u','t','r','q','p','n','m','l','k']\
                  [total%11]

# s or t prefix
else:
    calc_suffix = ['j','z','i','h','g','f','e','d','c','b','a']\
                  [total%11]

assert (calc_suffix == suffix), "invalid suffix or wrong digits. calculations \
        yield the suffix to be {}.".format(calc_suffix.upper())

print("NRIC: {0} is valid!".format(nric))