Question

我的代码应输出：

Encipher
Enter 1 to encipher or 2 to decipher: 1
Enter text you wish to encipher: My dog has fleas.
Enter the number of characters to shift: 7
The encrypted text is: Fr whz atl yextl.
Decipher
Enter 1 to encipher or 2 to decipher: 2
Enter text you wish to decipher: Fr whz atl yextl.
The most likely shift is: 7
My dog has fleas.

但它不起作用，我不明白如何使用try / except使我的代码执行此操作。

while True: 
    try: 
        num = int(raw_input('Enter 1 or 2:'))
        break
    except ValueError: 
        print "You have to enter 1 or 2, try again"

    if (num == 1):
        num = int(raw_input('Enter a number:'))
        num = int(raw_input('encipher'))
        print "Enter text to encipher"
        print "Enter the number of characters you want to shift" 

    elif (num == 2):
        num = int(raw_input('Enter a number:'))
        num = int(raw_input('decipher'))
        print "Enter text to decipher"
        print "Enter the number of characters you want to shift"

Answer 1

您的直接问题是，除了输入的数字与您打印的文字不匹配外，您不会得到。 Python不会自动读取和解释您发送到屏幕的消息。相反，在顶部尝试这一点：进入一个坚持法律数据的无限循环。继续前进，直到获得合法数据。抓住每个号码，检查一下是否合法;如果符合您的需要，请退出循环。

while True:
    while True:
        num = int(raw_input('Enter 1 or 2:'))
        if num in [1,2]:
            break
        print "You have to enter 1 or 2, try again"

    if (num == 1):
        ...

你做得很好，只需编写几行代码，然后再继续工作。请注意，较低的代码中存在一些概念性问题。对于isntance，您要求用户输入要加密的文本，但之后您尝试将其转换为整数。那会让你得到ValueError。

如果再次卡住，请发布一个新问题。

在Python中尝试/除外

1 个答案: