Python银行登录程序中balance变量无法保留值问题求助

你的问题核心是每次操作后没有更新balance变量本身：你在取款、存款时计算了新余额存在total里，但始终没把新值赋值回balance，导致balance一直保持初始的100，每次操作都基于原始值计算，看起来像是被重置了。

修改后的代码 #

import time
username = "user"
password = "123"
login_count = 0

while True:
    login_count += 1
    if login_count > 3:
        print("try again later")
        break
    user = input("what is your username?  ")
    pas = input("what is your password?  ")
    if user == username and pas == password:
        print("login in...")
        time.sleep(2)
        print("correct!")
        break

balance = 100
while True:
    if login_count > 3:
        break
    option = input("\nwould you like to do: \nwithdraw \ndeposit \nview \nexit \n  ").strip().lower()
    if option == "withdraw":
        withdraw = float(input("how much would you like to withdraw?  "))
        if balance - withdraw < 0:
            print("you cannot take out that much")
            continue
        balance -= withdraw
        print("here is your new balance:  ", balance)
    elif option == "deposit":
        deposit = float(input("how much would you like to deposit?  "))
        balance += deposit
        print("here is your new balance: ", balance)
    elif option == "view":
        print("here is your balance: ", balance)
    elif option == "exit":
        print("login out...")
        time.sleep(2)
        print("thank you for being a loyal customer!")
        break
    else:
        print("Invalid option, please try again.")

关键修改点 #

• 取款/存款操作：直接用balance -= withdraw、balance += deposit更新余额，不再依赖临时变量，确保balance实时保存最新值
• 输入优化：strip().lower()让用户输入的大小写、前后空格不影响功能判断（比如输入" Withdraw "也能被识别）
• 新增无效选项提示，避免用户输入错误后无反馈

修改后balance会在每次操作后保留更新值，直到程序退出。

内容的提问来源于stack exchange，提问作者Mozza