How to check if string contains only valid amount of spaces

Question

I need to write code that checks if a certain input string is valid. It must:

Contain a "space" in the input string which separates words
Not contain multiple consecutive spaces in a row
Not contain just a "space" (just single space as an input).

Here is what I mean:

username = str(input())
print(username)

username = "two apples" # acceptable

username = "two apples and pears" # acceptable

username = "two' '' 'apples" # not acceptable (because of 2 spaces in a row or more)

username = " " # not acceptable (because of single space with no other words.) 

username = "' '' '' '' '' '' '" #not acceptable because of multiple spaces (didn't know how to type it in here better to clarify.

`if username == " " or " " in username: print("Invalid username")`? — Selcuk, Nov 09 '21 at 04:53
yes I tried that, but this will not work if the username == " " # 3 or 4 or5 or any other number of spaces. — Yura Hardzeyevskyy, Nov 09 '21 at 04:56
@Swagrim also tried that, but then I won't be able to input "one two" # with a space between words — Yura Hardzeyevskyy, Nov 09 '21 at 05:01
@YuraHardzeyevskyy I'd try out the suggestion above, as checking if there are two spaces `" "` in a string should work if a string contains 2 or more spaces in a row also. — rv.kvetch, Nov 09 '21 at 05:06
For the fourth case in the question, to check if a string is only spaces you can try `if not s.strip():` which should help catch such scenarios. — rv.kvetch, Nov 09 '21 at 05:08

Grace · Answer 1 · 2021-11-09T05:20:43.220

0

I recognize that this might be slightly different than what you are directly asking for, but why not strip the extra spaces from the username input? You could use regex to quickly strip them out per this answer.

If you simply want to return an invalid input, I would again use regex.

import re

username = str(input("Please enter your username: "))
if re.search(" {2,}", username):
  print("Please do not include multiple spaces in a row in your username!")
else:
  # Do the rest of your program.

edited Nov 09 '21 at 05:20

answered Nov 09 '21 at 05:06

Grace

315
3
10

1

a good suggestion nevertheless, but a simple `in` condition as mentioned, i.e. such as `' ' in 'The quick brown fox'`, seems to be the fastest option available in Python from what I can tell (even beating out regex for this use case) – rv.kvetch Nov 09 '21 at 05:12
1

@rv.kvetch that's probably true, I didn't really do any performance testing. Regex was on the brain though when I was thinking about stripping extra space, rather than just checking if the space *existed*, so I went straight to "just search with regex." – Grace Nov 09 '21 at 05:15
1

Doesn't that regex also catch single spaces? Did you mean `" {2,}"`? – Selcuk Nov 09 '21 at 05:18
1

I did in fact mean `" {2,}"`, thank you for the catch. – Grace Nov 09 '21 at 05:20

Swagrim · Answer 2 · 2021-11-09T12:08:16.630

0

I was having my online class, so I couldn't do on time. Now I can give the the answer.

Here's the code. It's pretty simple to understand too.

username = input()
if ("  ") in username:
    print("Eh!")
elif username.isspace():
    print("Ew!")
else:
    print(username)

And BTW you don't need to use str() in the input as it takes a string input by default.

edited Nov 09 '21 at 12:08

answered Nov 09 '21 at 05:35

Swagrim

422
4
17

score 0 · Answer 3 · answered Nov 09 '21 at 13:07

Here is the code you are looking for I believe. Please test with different test cases and comment if something is wrong. I tried with all your test cases.

def checkspace(string):
    if string:
        for idx,i in enumerate(string):
            try:
                if (string[idx] == ' ' and string[idx+1] ==' '):
                    return 'String is Not Perfect'
            except:
                return 'String is Not Perfect'
            
        print('String is Perfect')
    else:
        return 'No String At AlL'

Eg:

string="two apples"
checkspace(string)
  
output:
"String is Perfect"

Eg:

string="two  apples"
checkspace(string)
      
output:
"String is Not Perfect"

How to check if string contains only valid amount of spaces

3 Answers3