Python 从我的程序中获取我无法理解的错误

我正在为我的初级python类编写一个用于信用卡验证的程序，使用Luhn算法来输出用户输入的信用卡号码是否有效，并且我遇到了一些不知道如何修复的错误。任何比我聪明的人都能看出我的代码有什么问题吗。非常感谢大家

def main():
    # user will input the credit card number as a string
    # call the function isValid() and print whether the credit card number is valid or not valid
    number = int(input("Enter a Credit Card Number as a Long Integer: "))

    if isValid(number):
        print(number, "is Valid.")
    else:
        print(number, "is Not Valid.")

def isValid(number):
    # Return true if the card number is valid
    # You will have to call function sumOfDoubleEvenPlace() and sumOfOddPlace()
    return (str(number).startswith("4") or str(number).startswith("5") or str(number).startswith("37")) and \
           (sumOfDoubleEvenPlace(number) + sumOfOddPlace(number)) % 10 == 0

def sumOfDoubleEvenPlace(number):
    # Sum of all single-digit numbers from step one
    total = 0

    for num in range(len(str(number)) -2, -1, -2):
        total += getDigit(int(number[num]) * 2)

    return total

def getDigit(number):
    # Return the number if it is a single digit, otherwise return
    # the sum of the two digits
    return number % 10 + (number // 10 % 10)

def sumOfOddPlace(number):
    total = 0

    for num in range(len(number) -1, -1, -2):
        total += int(number[num])

    return total


main()

修正了代码：

def main():
    number = input("Enter a credit card number as a string: ").strip()

    if isValid(number):
        print(number, "is valid")
    else:
        print(number, "is invalid")


# Return true if the card number is valid
def isValid(number):
    return (number.startswith("4") or number.startswith("5") or
            number.startswith("6") or number.startswith("37")) and \
           (sumOfDoubleEvenPlace(number) + sumOfOddPlace(number)) % 10 == 0


# Get the result from Step 2
def sumOfDoubleEvenPlace(cardNumber):
    result = 0

    for i in range(len(cardNumber) - 2, -1, - 2):
        result += getDigit(int(cardNumber[i]) * 2)

    return result


# Return this number if it is a single digit, otherwise, return
# the sum of the two digits
def getDigit(number):
    return number % 10 + (number // 10 % 10)


# Return sum of odd place digits in number
def sumOfOddPlace(cardNumber):
    result = 0

    for i in range(len(cardNumber) - 1, -1, -2):
        result += int(cardNumber[i])

    return result

main()

---

与此代码中的其他地方一样，您需要一个字符串：

str（number）[num]

而不是

number[num]

我应该在哪里将number变量转换为str？将错误所指行中的

number

替换为

str（number）

（如我的回答中所述）。