Python Credit Card Number Generator

# Copyright (c) 2021 Adam Charvát

# Visa
# - MII: 4
# - IIN: (4)
# - Length: 13 or 16 digits

# Mastercard
# - MII: 5
# - IIN: (51 - 55)
# - Length: 16 digits

# American Express
# - MII: 3
# - IIN: (34, 37)
# - Length: 15 digits

import random
from enum import Enum

class Card(Enum):
    Visa = 0
    Mastercard = 1
    AmericanExpress = 2

def computeCheckDigit(cardNumber):
    total = 0
    digits = cardNumber[::-1]
    for i in range(len(digits)):
        digit = int(digits[i])
        if i % 2 == 0:
            digit *= 2
        total += sum(map(int, str(digit)))
    return (total * 9) % 10

def fillToLength(text, length):
    toAdd = length - len(text)
    for _ in range(toAdd):
        text += str(random.randint(0, 9))
    return text

def genCardNumber(cardType):
    if cardType == Card.Visa:
        length = 16
        prefix = str(4)
    elif cardType == Card.Mastercard:
        length = 16
        prefix = str(random.randint(51, 55))
    elif cardType == Card.AmericanExpress:
        length = 15
        prefix = str(random.choice([34, 37]))
    else:
        raise Exception("Invalid card type!")
    cardNumber = fillToLength(prefix, length - 1)
    return cardNumber + str(computeCheckDigit(cardNumber))

print("Visa: " + genCardNumber(Card.Visa))
print("Mastercard: " + genCardNumber(Card.Mastercard))
print("American Express: " + genCardNumber(Card.AmericanExpress))