Keep encountering "string index out of range' error in Python

Question

I'm doing an assignment for an intro course in which I need to determine whether a string is a palindrome. Having trouble with this segment of the code:

    def is_palindrome(letters): 
         if (len(letters))==0:
             return True
         elif len(letters)==1:
             return True
         elif (letters[end])==(letters[0]):
            return is_palindrome(letters[(letters[0+1]):(letters[len(letters)-1])])
         else:
            return False

1. I feel like `return is_palindrome(letters[(letters[0+1]):(letters[len(letters)-1])])` should be `return is_palindrome(letters[1:-1])` . 2. `def is_palindrome(letters): return letters == letters[::-1]` — NightShadeQueen, Sep 24 '15 at 02:09

Remi Guan · Answer 1 · 2015-09-24T02:22:50.787

2

Try these following codes:

def palindrome(text):
    if text == text[::-1]:
        print(text, 'is palindrome')
    else:
        print(text, 'is not palindrome')

palindrome('reser')
palindrome('reset')

str[::-1] will reverse the string. for more info, try help(slice).

edited Sep 24 '15 at 02:22

answered Sep 24 '15 at 02:09

Remi Guan

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This is a different method than what the OP tried - of course, it works, but does it teach him to correct his mistake? – Reblochon Masque Sep 24 '15 at 02:16
@ReblochonMasque Well, I think this way is more clearer and simpler. However you've just post an answer that correct his mistake ;) – Remi Guan Sep 24 '15 at 02:17
1

Your code as it is returns erroneous answers - please fix it. :) – Reblochon Masque Sep 24 '15 at 02:20
1

@ReblochonMasque Finished, I forgot change `str[::1]` to `str[::-1]`. Thanks :) – Remi Guan Sep 24 '15 at 02:23

score 2 · Accepted Answer · edited May 23 '17 at 10:27

2

Your code is nearly correct, but you have errors in the slicing of the strings:

def is_palindrome(letters): 
    if (len(letters))==0:
        return True
    elif len(letters)==1:
        return True
    elif (letters[0])==(letters[-1]):       # index [-1] gives the last letter
        return is_palindrome(letters[1:-1]) # slice [1:-1] is the word without the first and last letter.
    else:
        return False

The above works.

I suggest you review this post that explains in details how slicing works: Explain Python's slice notation

edited May 23 '17 at 10:27

Community

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answered Sep 24 '15 at 02:12

Reblochon Masque

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1

great resource. the link helped out a friend who was struggling with the splicing. +1 – Joseph Farah Sep 24 '15 at 02:37
1

@OliverChild-Lanning Now you should accept this answer. – Remi Guan Sep 24 '15 at 02:46

Keep encountering "string index out of range' error in Python

2 Answers2