Leetcode 520 Detect Capital

# 送分题
class Solution(object):
    def detectCapitalUse(self, word):
        """
        :type word: str
        :rtype: bool
        """
        if len(word)==1:
            return True
        
        ans=True
        if self.is_uppercase(word[0]):
            if self.is_uppercase(word[1]):
                for c in word[1:]:
                    if self.is_lowercase(c):
                        return False
            else:
                for c in word[1:]:
                    if self.is_uppercase(c):
                        return False
            return True
        else: # the first letter is lowercase
            for c in word[1:]:
                if self.is_uppercase(c):
                    return False
        return True
    def is_uppercase(self,letter):
        return (letter>=‘A‘)&(letter<=‘Z‘)
    def is_lowercase(self,letter):
        return (letter>=‘a‘)&(letter<=‘z‘)