如何使用python进行编程？(if-else，while，continue)

Question

我正在学习用Python编程，但我现在解决不了这个问题。

在第11行和第13行，如果取款被拒绝，我想让它重复第10行input("Enter amount of withdrawal")...but使用continue to to selection=input("Make a selection from the option menu:")。我该怎么办？

balance=1000
print("Options:\n1. Make a Deposit\n 2. Make a Withdrawal\n3. Obtain Balance\n4. Quit")
while True:
selection=input("Make a selection from the option menu:")
if selection=='1':
    deposit=float(input("Enter amount of deposit:"))
    balance+=deposit
    print("Deposit Processed.")
if selection=='2':
    withdrawal=float(input("Enter amount of withdrawal:"))
    if withdrawal>balance:
        print("Denied. Maximum withdrawal is $","{0:,.2f}".format(balance))
        continue                  # ***In this process, if withdrawal is denied, I wanna the 10th row..but using continue goes to selection=input("Make a selection from the option menu:") . What should I do?***
    if withdrawal<=balance:
        balance-=withdrawal
        print("Withdrawal Processed.")
if  selection=='3':
    print('$','{0:,.2f}'.format(balance))
if selection=='4':
    break

Answer 1

假设从第4行开始的所有内容都在while循环中，您唯一需要添加的就是if selection=='2'块中的另一个for循环：

if selection == '2':
    while True:
        withdrawal = float(input("Enter amount of withdrawal:"))

        if withdrawal > balance:
            print("Denied. Maximum withdrawal is $", "{0:,.2f}".format(balance))
        else:
            balance -= withdrawal
            print("Withdrawal Processed.")
            break

旁注:您可以考虑使用elif和else语句来提高代码的可读性，而不是使用连续的if语句：

balance = 1000
print("Options:\n1. Make a Deposit\n2. Make a Withdrawal\n3. Obtain Balance\n4. Quit")
while True:
    selection = input("Make a selection from the option menu:")
    if selection == '1':
        deposit = float(input("Enter amount of deposit:"))
        balance += deposit
        print("Deposit Processed.")
    elif selection == '2':
        while True:
            withdrawal = float(input("Enter amount of withdrawal:"))

            if withdrawal > balance:
                print("Denied. Maximum withdrawal is $", "{0:,.2f}".format(balance))
            else:
                balance -= withdrawal
                print("Withdrawal Processed.")
                break
    elif selection == '3':
        print('$', '{0:,.2f}'.format(balance))
    elif selection == '4':
        break