在循环中使用if标记检查user_input

Question

I am trying to write a function that checks my input to see whether I have entered the character '?'.

This is what I got so far:

def check_word():
   word = []
   check = 0
   user_input = input('Please enter a word that does not contain ?: ')

   for token in user_input.split():
      if token == '?':
        print('Error')
check_word()

My input: hello?
It is supposed to show 'Error'. But it doesn't show anything. Could you please tell me what wrong it is in my code.

Answer 1

I would use the in operator to do this

def check_word(s):
    if '?' in s:
        print('Error')

For example

>>> check_word('foobar')
>>> check_word('foo?')
Error

Answer 2

The problem is how you split the string of the user_input .

user_input.split():

The example doesn't contain whitespaces so the condition isn't met. If you want for example to check a sentence with spaces, you should split it like this: user_input.split(' ') to split it on the spaces.

But for this example you have two choices:

1) You can just iterate over the input itself because you want to check every char in the string for whether it's a ? .

That is, change user_input.split(): into simply user_input without splitting. This option is good if you might ever want to add some sort of action for each char.

2) It's very easy just to use in , like this:

if '?' in s:
    print('There is a question mark in the string')

This is a very simple solution that you can expand and check for other chars in the string as well.

Answer 3

It's because user_input.split() splits the user_input by whitespace. Since hello? does not contain any whitespaces, token is equal to your input and the loop is executed once.

You should iterate over user_input instead, or simply check if '?' in user_input if '?' in user_input .