Python类型错误不支持的操作数

Question

我在这里有一个示例程序，当我运行它并选择一个选项但返回以下错误时，我看不到问题。

TypeError: unsupported operand type(s) for -: 'str' and 'int'

#Exception Handling 

#If you haven't seen them before, you're not trying hard enough. What are they? Errors. Exceptions. Problems. Know what I'm talking about? I got it with this program: 

#Code Example 1 - buggy program 
def menu(list, question): 
    for entry in list: 
     print (1 + list.index(entry),) 
     print (")" + entry) 

    return input(question) -1 

answer = menu(['A','B','C','D','E','F','H','I'],\ 
'Which letter is your favourite?') 

print ('You picked answer ' + (answer + 1)) 

Answer 1

如果使用Python3然后input(question)返回字符串'1'，'2'，等等。你必须把它转换成数字int(input(question))。