Question

我的代码输出应该是这样的：

加密器：

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.

破译：

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.

到目前为止，我有这个并且我一直得到无效的语法。我对如何在输出中输入答案感到困惑。它应该是try / except with while循环，因为它是一个学校作业。

while True: 
    try: 
        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):
        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

你不一定非常需要使用try / except，但是如果你想尝试将转换转换为整数然后就可以了。主要问题是你在任何地方都没有一个except块。

while True:
    try:
        num = int(raw_input('Enter 1 or 2:'))
        if num in [1,2]:
            break
    except ValueError as e:
        print "You didn't enter a number.  Try again"

Answer 2

您没有正确使用try-except。想法是尝试一大堆代码;但如果遇到错误/异常，请做其他事情。

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

在你的脚本中，你试图接受一个数组中的int，并且你正在处理一个不在预定义选项列表中的场景。但是，如果它们是该代码块的例外，那么您没有做任何事情。

要使用try-except，请执行以下操作：

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

尝试/除了错误Python？

2 个答案: