多次更改循环中变量的值

Question

我有一个银行程序，您可以在其中执行多项操作，并且 var 余额需要根据用户输入进行更新。它第一次这样做，并在下一个运行中使用新值。但是，如果您运行第三次循环，它会在第一次运行中使用平衡输出，而不是第二次。如果你运行它四次，它仍然使用第一个值，依此类推。

我对编程还是很陌生，但我的理论是第二个循环无法 return 平衡的新值，所以它只会卡在第一个循环上。但我不知道如何解决这个问题。

这里有人有什么想法吗？谢谢。

balance = 500
def main(balance):
    menu = int(input('Press 1 for balance, 2 for deposit, 3 for withdrawal or 4 for interest return: '))
    print()
    if menu == 1:
        print(balance)
    elif menu == 2:
        dep = int(input('How much do you want to deposit? '))
        print()
        balance = (balance + dep)
        print('Your new balance is', balance)
        print()
        if balance <= 999999:
            interest = 0.01
            print('Your interest is standard, 0.01%')
        if balance >= 1000000:
            interest = 0.02 
            print('Your intrest is premium, 0.02%!')
    elif menu == 3:
        wit = int(input('How much do you want to withdraw? '))
        print()
        balance = (balance - wit)
        print('Your new balance is', balance)
        print()
        if balance <= 999999:
            interest = 0.01
            print('Your intrest is standard, 0.01%')
        if balance >= 1000000:
            interest = 0.02
            print('Your interest is premium, 0.02%!')
    elif menu == 4:
        if balance <= 999999:
            interest = 0.01
        if balance >= 1000000:
            interest = 0.02
        interest_return = (balance * interest)
        balance = (balance + interest_return)
        print('Your interest is', interest, 'that makes your intrest return', interest_return, 'and your new balance', balance)
    return balance
balance = main(balance)
while True:
    print()
    restart = str(input('Would you like to do more? Press y for yes or n for no: '))
    if restart == 'n':
        print('Thank you for using the automatic bank service!')
        break
    elif restart == 'y':
        main(balance)
    else:
        print()
        print('Invalid input, press y for yes or n for no')
        continue

Answer 1

您需要使用用户输入更新 while 循环中的 balance 变量。将行 main(balance) 更新为 balance = main(balance)

Answer 2

tldr;

balance = 500
while True:
    print()
    restart = str(input('Would you like to do more? Press y for yes or n for no: '))
    if restart == 'n':
        print('Thank you for using the automatic bank service!')
        break
    elif restart == 'y':
        balance = main(balance) ########### HERE
    else:
        print()
        print('Invalid input, press y for yes or n for no')
        continue

解释：在您的原始代码中，您在每个循环中都分配了新值，因此

balance(main)

总是从分配的值开始，并且从不更改它，因为在 main 函数的范围内更改被添加到 local 平衡，而在函数之外你有全球平衡。功能正在对本地进行更改，返回并打印本地，而全局始终相同。为了更好地理解这一点，尽量不要将局部变量和全局变量命名为相似的，例如：

def main(local_balance):
    menu = int(input('Press 1 for local_balance, 2 for deposit, 3 for withdrawal or 4 for interest return: '))
    print()
    if menu == 1:
        print(local_balance)
    elif menu == 2:
        dep = int(input('How much do you want to deposit? '))
        print()
        local_balance = (local_balance + dep)
        print('Your new local_balance is', local_balance)
        print()
        if local_balance <= 999999:
            interest = 0.01
            print('Your interest is standard, 0.01%')
        if local_balance >= 1000000:
            interest = 0.02
            print('Your intrest is premium, 0.02%!')
    elif menu == 3:
        wit = int(input('How much do you want to withdraw? '))
        print()
        local_balance = (local_balance - wit)
        print('Your new local_balance is', local_balance)
        print()
        if local_balance <= 999999:
            interest = 0.01
            print('Your intrest is standard, 0.01%')
        if local_balance >= 1000000:
            interest = 0.02
            print('Your interest is premium, 0.02%!')
    elif menu == 4:
        if local_balance <= 999999:
            interest = 0.01
        if local_balance >= 1000000:
            interest = 0.02
        interest_return = (local_balance * interest)
        local_balance = (local_balance + interest_return)
        print('Your interest is', interest, 'that makes your intrest return', interest_return, 'and your new local_balance', local_balance)
    return local_balance

global_balance = 500
while True:
    print()
    restart = str(input('Would you like to do more? Press y for yes or n for no: '))
    if restart == 'n':
        print('Thank you for using the automatic bank service!')
        break
    elif restart == 'y':
        global_balance = main(global_balance)
    else:
        print()
        print('Invalid input, press y for yes or n for no')
        continue

多次更改循环中变量的值

Change value of variable in a loop, multiple times

python

loops

var

return