Simple python utility capable of verifying DNI and guessing the last character

dni_tool.py

#!/usr/bin/python3


# Based on: https://calculadorasonline.com/calcular-la-letra-del-dni-validar-un-dni/

# 1. Get the numeric part of the DNI
# 2. Get the remainder of: n mod 23
# 3. The last character is assigned based on the remainder

import sys

def check_character(src_char, found_char):
    if src_char == found_char:
        print("The DNI is valid")
    else:
        print("The DNI is not valid")

if len(sys.argv) <= 2:
    print("Usage: python3 " + sys.argv[0] + " verify <dni> \t\t(check if a DNI is valid)")
    print("Usage: python3 " + sys.argv[0] + " guess <dni w/o char> \t(guess the last character of a DNI based on the numbers)")
    print()
    print("Example: python3 " + sys.argv[0] + " verify 50235402K")
    print("Example: python3 " + sys.argv[0] + " guess 50235402")
    sys.exit(0)

# Parse mode
mode = sys.argv[1]

# Parse CLI argument
dni = sys.argv[2]

# Pad DNI with zeros
if mode == "verify":
    dni = dni.zfill(9)
    # Get only the number
    num = dni[:-1]
    # Get only the character
    char = dni[-1]

elif mode == "guess":
    dni = dni.zfill(8)
    num = dni

res = int(num) % 23

match res:
    case 0:
        found_char = "T"
    case 1:
        found_char = "R"
    case 2:
        found_char = "W"
    case 3:
        found_char = "A"
    case 4:
        found_char = "G"
    case 5:
        found_char = "M"
    case 6:
        found_char = "Y"
    case 7:
        found_char = "F"
    case 8:
        found_char = "P"
    case 9:
        found_char = "D"
    case 10:
        found_char = "X"
    case 11:
        found_char = "B"
    case 12:
        found_char = "N"
    case 13:
        found_char = "J"
    case 14:
        found_char = "Z"
    case 15:
        found_char = "S"
    case 16:
        found_char = "Q"
    case 17:
        found_char = "V"
    case 18:
        found_char = "H"
    case 19:
        found_char = "L"
    case 20:
        found_char = "C"
    case 21:
        found_char = "K"
    case 22:
        found_char = "E"

if mode == "verify":
    check_character(char, found_char)
elif mode == "guess":
    print("The DNI should be: " + dni + found_char)