Valid Palindrome.md

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Note: For the purpose of this problem, we define empty string as valid palindrome.

Example 1:

Input: "A man, a plan, a canal: Panama"
Output: true
Example 2:

Input: "race a car"
Output: false

My code:

class Solution(object):
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        tmp_str=""
        for c in s:
            if ord(c)>=65 and ord(c)<=90:
                tmp_str+=c.lower()
            if ord(c)>=97 and ord(c)<=122:
                tmp_str+=c
            if ord(c)>=48 and ord(c)<=57:
                tmp_str+=c
        return tmp_str==tmp_str[::-1]

Solution: https://leetcode.com/problems/valid-palindrome/