check whether a string contains a character in python

Question

I am trying to compare and see if a particular character exists in the string, but when i try to access the character which is in another string, its throws an error 'argument of type 'int' is not iterable'. How do i access the character from a string without causing the error?

    def lengthOfLongestSubstring(self, s: str) -> int:
        longStrLen = 0
        totalStrLen = len(s)

        holderString = ""
        holderString += s[0]
        longStrLen = 0

        for i in range(1,totalStrLen-1):

            if s[i] not in holderString:
                holderString += s[i]
            else:
                if longStrLen < len(holderString):
                    longStrLen = len(holderString)
                holderString = 0

        return longStrLen

TypeError: argument of type 'int' is not iterable at Line 
if s[i] not in holderString:

holderString = 0 You've reassigned holderString to an integer, and it's not a string any more. — John Gordon
– John Gordon, Commented May 24, 2019 at 17:05
Specifically when you check whether the character exists in the string, you set the whole holderstring to 0 when you encounter a duplicate letter. cat will run but caaat will not — G. Anderson
– G. Anderson, Commented May 24, 2019 at 17:10
Why is this a method? You don't use self anywhere in the body. — chepner
– chepner, Commented May 24, 2019 at 17:10
What exactly is the function supposed to do? It appears that you just want the index of the first repeated character. — chepner
– chepner, Commented May 24, 2019 at 17:11
@chepner I would assume due to the inclusion of self it's from a class, but for the minimal reproducible example, the asker (correctly) only provided the nonworking snippet of code — G. Anderson
– G. Anderson, Commented May 24, 2019 at 17:14

Alec · Accepted Answer · 2019-05-24 17:24:56Z

3

Your problem is on this line:

holderString = 0

You reassigned the holderString variable to the integer 0. While strings can be iterated over, integers cannot. You attempt to iterate over the new integer on this line:

if s[i] not in holderString:

which causes the error.

There is a much better way to approach a function that returns the first repeated character though. Simply use the index() method:

def findChar(char, string):
    for c in string:
        if c == char: 
             return string.index(c)

edited May 24, 2019 at 17:24

answered May 24, 2019 at 17:10

Alec

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Comments

chepner · Accepted Answer · 2019-05-24 17:19:40Z

0

It appears you only need to count unique characters until you find the first duplicate. You can do that with a set.

def longest_substring(s: str) -> int:
    seen = set()
    for c in s:
        if c in seen:
            break
        seen.add(c)
    return len(seen)

answered May 24, 2019 at 17:19

chepner

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