Leetcode_Python 58 最后一个单词的长度

class Solution(object):
    def lengthOfLastWord(self, s):
        """
        :type s: str
        :rtype: int
        """
        last_num = 0
        length = len(s)
        if s == 0:
            return last_num
        else:
            for i in range(length-1,-1,-1):
                if s[i] != " ":
                    last_num += 1
                if s[i] == " " and last_num != 0:
                    break
            return last_num