Check user input against a list of characters

Question

I am trying to take user input as a string and check it against a list of characters, I want the user to create a word using only characters from the list.

So far I can check that the first letter is correct but any more than that and my test fails!

wordInput = str(input("words please: "))
if wordInput in ['w', 'v', 'g']:
print("yes")
else:
    print("no")

I'm not sure how I can take the input and split it so that my test recognizes each individual character of the input rather than testing the input literally against the characters in the list.

Any help would be gratefully received, Thank you

use a for in loop to go through each letter at a time `for letter in word_input:` — Chris Doyle, Mar 19 '20 at 12:16
Don't need to use `str(input(..`, – it already [returns a string](https://docs.python.org/3/library/functions.html#input). — Jongware, Mar 19 '20 at 12:24
not too sure why I've been marked down? if you would like to explain I would be more than happy to edit my question — Mortgage1, Mar 19 '20 at 12:31
You could have written this with a simple loop. So far, the answers below use more advanced techniques (more "pythonic") but looping over `word_input` and testing one character at a time is not entirely illogical. (Also, your indentation is bad. Also, you are not testing "that the first letter is correct... it only works on *one* letter inputs.) — Jongware, Mar 19 '20 at 12:33
Ah – you did not *know* there was a `for` in Python? Check out the [official Python Tutorial](https://docs.python.org/3/tutorial/controlflow.html#for-statements), "4.2. `for` Statements". — Jongware, Mar 19 '20 at 12:38

bruno desthuilliers · Answer 1 · 2020-03-19T12:29:35.353

1

The pythonic way here is to use sets:

def validate_input(userword, accepted_chars):
    return set(accepted_chars).issuperset(userword)

def main():
    # input() always returns a string in Py3    
    userword = input("words please:")
    if validate_input(userword, "wvg"):
        print("ok")
    else:
        print("ko")

if __name __ "__main__":
    main()

edited Mar 19 '20 at 12:29

answered Mar 19 '20 at 12:21

bruno desthuilliers

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@schwobaseggl oops - you're of course right, my bad – bruno desthuilliers Mar 19 '20 at 12:24
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@schwobaseggl fixed ;-) thx for correcting me. – bruno desthuilliers Mar 19 '20 at 12:29

Jongware · Answer 2 · 2020-03-19T12:36:58.700

1

The pythonic way here is to use all:

word_input = input("words please: ")
if all(ch in ['w','v','g'] for ch in word_input):
    print("yes")
else:
    print("no")

.. for ch in word_input yields every character in word_input one by one. As soon as the test ch in [..] fails, all will return False; if all tests pass, it returns True.

edited Mar 19 '20 at 12:36

answered Mar 19 '20 at 12:29

Jongware

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`... ch in 'wvg'...` will look even cleaner. – user2390182 Mar 19 '20 at 12:30
1

@schwobaseggl: that's what I initially had, but OP uses a list. It may be for other reasons. There is no functional difference, so I used that as well. – Jongware Mar 19 '20 at 12:31

score 0 · Accepted Answer · answered Mar 19 '20 at 12:16

0

One way is to match all characters against the master list .

wordInput = str(input("words please: "))
only_valid_characters = ['w', 'v', 'g']
validatedInput = [valid_char for valid_char in wordInput if valid_char in only_valid_characters]

if len(wordInput) == len(validatedInput):
    print("yes")
else:
    print("no")

answered Mar 19 '20 at 12:16

Kris

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Thank you so much for your help, your answer makes perfect sense! – Mortgage1 Mar 19 '20 at 12:27
You can accept the answer if it worked! :-) – Kris Mar 19 '20 at 12:31
This checks if all valid characters are used, not if all used characters are valid – user2390182 Mar 19 '20 at 12:32
It reconstructs the string with used valid characters. Length match is done to make sure everything was valid! I dont know why there was a down vote! – Kris Mar 19 '20 at 12:34

Check user input against a list of characters

3 Answers3