Update 0005.最长回文子串.md

Added python version code

problems/0005.最长回文子串.md

@@ -270,6 +270,23 @@ public:
 ## Python
 
 ```python
+class Solution:
+    def longestPalindrome(self, s: str) -> str:
+        dp = [[False] * len(s) for _ in range(len(s))]
+        maxlenth = 0
+        left = 0
+        right = 0
+        for i in range(len(s) - 1, -1, -1):
+            for j in range(i, len(s)):
+                if s[j] == s[i]:
+                    if j - i <= 1 or dp[i + 1][j - 1]:
+                        dp[i][j] = True
+                if dp[i][j] and j - i + 1 > maxlenth:
+                    maxlenth = j - i + 1
+                    left = i
+                    right = j
+        return s[left:right + 1]
+
 ```
 
 ## Go