Get Odd Length Palindrome

Question

I'm trying to find the longest odd length palindrome, but the code I've written isn't giving me the full palindrome, just part of it. Any help would be great!

def get_odd_palindrome_at(s, index):
    ''' (str, int) -> str

    > get_odd_palindrome_at('tbababt', 3)
    'tbababt'
    > get_odd_palindrome_at('color', 2)
    'olo'
    '''

    palindrome = s[index]
    i = index

    for char in s:
        if s[i - 1] == s[i + 1]:
            palindrome = s[i - 1] + palindrome + s[i + 1]
            i = i + 1

    return palindrome

Answer 1

Make i the distance from the index and make sure not to loop out of bounds. Finally, only build the result string when you have found the final value of i. There is no use in doing it in every iteration:

def get_odd_palindrome_at(s, index):
    for i in range(1, index+1):
        if index + i >= len(s) or s[index - i] != s[index + i]:
            i -= 1
            break

    return s[index-i:index+i+1]

Alternatively, you could use two variables, which simplifies the code a bit:

def get_odd_palindrome_at(s, index):
    i = index
    j = index
    while i >= 0 and j < len(s) and s[i] == s[j]:
        i -= 1
        j += 1

    return s[i+1:j]