Longest text substring （ secondary ）

def longestPalindrome(self, s):   # There are two situations , One is an odd number of palindromes , Another kind # Is an even number of palindromes 
        res = ''
        for i in range(len(s)):    # Traverse the entire array ,i For the pointer 
            start = max(i - len(res) -1, 0)
            t = s[start: i+1]
            if t == t[::-1]:
                res = t
            else:     
                t = t[1:]         
                if t == t[::-1]:   #  According to the index range of the selected palindrome substring , Slice the string 
                    res = t
        return res

Integer inversion （ secondary ）

def reverse(self, x):
#  Convert integers to character types for inversion 
        x = str(x)
        res = ''
        #  If it is not a negative number, it will be reversed directly , Don't consider that the first one becomes 0, Because the character data needs to be converted into int data 
        if x[0] != '-':
            res = x[::-1]
        #  If it's a negative number , Put the first position into '-', Remove the last bit after reversing 
        else:
            res = '-' + x[::-1][0:-1]
        max, min = 1, 1
        for i in range(31):
            max *= 2
        min = -max
        if int(res) >= min - 1 and int(res) <= max:
            return int(res)
        else:
            return 0