Fun with learning about VINs

vin_checksum.py

transliteration_table = {
    "A": 1, "B": 2, "C": 3, "D": 4, "E": 5, "F": 6, "G": 7, "H": 8,
    "J": 1, "K": 2, "L": 3, "M": 4, "N": 5,         "P": 7,         "R": 9,
            "S": 2, "T": 3, "U": 4, "V": 5, "W": 6, "X": 7, "Y": 8, "Z": 9,
    "1": 1, "2": 2, "3": 3, "4": 4, "5": 5, "6": 6, "7": 7, "8": 8, "9": 9,
    "0": 0,
}

weights_table = [8,7,6,5,4,3,2,10,0,9,8,7,6,5,4,3,2]

def check_sum(vin: str):
    vin = vin.upper()
    # Check length of VIN
    if len(vin) != 17:
        print(f"error: VINs are 17 chars: {vin}")
        return False

    # Check for invalid characters in VIN
    if "I" in vin or "O" in vin or "Q" in vin:
        print(f"error: VINs do not contain I, O, or Q")
        return False

    check_value = vin[8] # Calculated checksum should match this value

    products = []
    pos = 0
    # Multiply each transliterated VIN char by position weight
    for char in vin:
        char_value = transliteration_table[char]
        weight_value = weights_table[pos]
        products.append(char_value * weight_value)
        pos += 1

    # sum mod 11 gives VIN checksum, if 10, char should be X
    sum_value = sum(products) % 11
    if sum_value == 10:
        return check_value == "X"
    if transliteration_table[check_value] != sum_value:
        print(f"VIN: {vin} failed check sum, expected {sum_value} but found {check_value}")
    return True

#True  == check_sum("VF1LM1B0H36666155")
#False == check_sum("")
#False == check_sum("111111111111111111")
#True  == check_sum("11111111111111111")
#True  == check_sum("1M8GDM9AXKP042788")