手动运行正常但while循环失效：Luhn算法卡号生成问题

我编写了以下Python代码，用来生成符合Luhn算法的信用卡号、有效期及CVV并写入CSV文件。手动运行时偶尔能得到有效卡号，但把校验逻辑放进while循环后，程序一直返回“Not valid”。我需要实现程序自动生成有效卡号，不用手动重复运行。

import random


def ranCardNum():
    ranCardNumls = []
    for i in range(0,16):
        ranNum = random.randint(0,9)
        ranCardNumls.append(ranNum)
    return ranCardNumls
#Gets random 16 digits long number and adds it to a list
        


def luhnAlgo(NoPrPro):
    #print("".join(str(n) for n in NoPrPro))
    
    for i in range(14,0,-2):
        NoPrPro[i] = NoPrPro[i] * 2
        if NoPrPro[i] >= 10:
            first = str(NoPrPro[i])[0]
            second = str(NoPrPro[i])[1]  
            NoPrPri= int(first) + int(second)
            NoPrPro[i] = NoPrPri 
            
    return "".join(str(n) for n in NoPrPro)
#The luhn algorithm returns number without the list
        
def endDate():
    dateM = random.randint(1,12)
    if dateM <= 9:
        letter = str(dateM)
        dateM = "0" + letter
    dateY = random.randint(2022,2026)
    
    return dateM, dateY
#generates random dates and returns them
    
def ranCvv():
    ranCvv = random.randint(100,1000)
    return ranCvv
#random 3 digit number and returns it
    

def writeCsv(cardNum,cardDay, cardYear, cvv):
    f = open("cardNo.csv","a")
    f.write(cardNum + ",")
    f.write(cardDay + ",")
    f.write(cardYear + ",")
    f.write(cvv + "\r")
    f.close()
#writes to my csv file
#Check - Taken from geeksforgeeks.org
def checkLuhn(cardNo):
     
    nDigits = len(cardNo)
    nSum = 0
    isSecond = False
     
    for i in range(nDigits - 1, -1, -1):
        d = ord(cardNo[i]) - ord('0')
     
        if (isSecond == True):
            d = d * 2

        nSum += d // 10
        nSum += d % 10
  
        isSecond = not isSecond
     
    if (nSum % 10 == 0):
        return True
    else:
        return False
    
cardNo = luhnAlgo(ranCardNum())

if __name__=="__main__": 
    if (checkLuhn(cardNo)):
        print(cardNo)
        expDay = str(endDate()[0])
        expYear = str(endDate()[1])
        cvv = str(ranCvv())
        writeCsv(cardNo, expDay,expYear, cvv)
    else:
        print("Not valid")

问题原因 #

你的luhnAlgo函数没有正确实现Luhn算法的生成逻辑——它只是对随机生成的16位数字中的部分位做了加倍拆分，但没有计算并设置校验位，导致生成的卡号几乎都不符合Luhn规则，手动运行成功只是极小概率的巧合。

解决方案 #

正确的Luhn卡号生成逻辑是：先生成前15位随机数字，再通过算法计算出第16位校验位，这样生成的卡号必然符合规则，无需循环重试。修改后的代码如下：

import random

def generate_valid_card_number():
    # 生成前15位随机数字
    prefix = [random.randint(0,9) for _ in range(15)]
    total = 0
    is_second = False
    
    # 按Luhn规则计算前15位的总和
    for digit in reversed(prefix):
        if is_second:
            digit *= 2
            total += digit // 10 + digit % 10
        else:
            total += digit
        is_second = not is_second
    
    # 计算校验位：让总和成为10的倍数
    check_digit = (10 - (total % 10)) % 10
    prefix.append(check_digit)
    return ''.join(map(str, prefix))

def endDate():
    dateM = random.randint(1,12)
    dateM = f"0{dateM}" if dateM <=9 else str(dateM)
    dateY = str(random.randint(2022,2026))
    return dateM, dateY

def ranCvv():
    return str(random.randint(100,999))

def writeCsv(cardNum, cardDay, cardYear, cvv):
    with open("cardNo.csv","a", encoding='utf-8') as f:
        f.write(f"{cardNum},{cardDay},{cardYear},{cvv}\n")

# 保留原校验函数用于验证（可选）
def checkLuhn(cardNo):
    nDigits = len(cardNo)
    nSum = 0
    isSecond = False
    for i in range(nDigits - 1, -1, -1):
        d = ord(cardNo[i]) - ord('0')
        if isSecond:
            d *= 2
        nSum += d // 10
        nSum += d % 10
        isSecond = not isSecond
    return nSum % 10 == 0

if __name__=="__main__": 
    cardNo = generate_valid_card_number()
    # 验证生成的卡号（可选步骤）
    if checkLuhn(cardNo):
        print(f"生成有效卡号：{cardNo}")
        expDay, expYear = endDate()
        cvv = ranCvv()
        writeCsv(cardNo, expDay, expYear, cvv)
    else:
        print("生成失败")

关键修改点 #

1. 新增generate_valid_card_number函数，严格按照Luhn算法生成有效卡号，确保每次生成的卡号都符合校验规则
2. 优化endDate和writeCsv的写法，用f-string简化字符串拼接，writeCsv改用with语句自动管理文件资源，避免泄漏
3. 主逻辑直接生成有效卡号，无需循环重试

内容的提问来源于stack exchange，提问作者nially