Longest Palindromic Substring LeetCode solution in Python

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# Runtime: 643 ms (Top 86.54%) | Memory: 14 MB (Top 58.84%)
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class Solution:
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    def longestPalindrome(self, s: str) -> str:
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        res = ""
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        for i in range(len(s)):
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            left, right = i - 1, i + 1
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            while right < len(s) and s[right] == s[i]:
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                right += 1
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            while 0 <= left < right < len(s) and s[left] == s[right]:
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                left, right = left - 1, right + 1
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            res = s[left + 1 : right] if right - left - 1 > len(res) else res
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        return res