[leetcode trie]211. Add and Search Word - Data structure design

Design a data structure that supports the following two operations:

void addWord(word)
bool search(word)

search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.

For example:

addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true

实现字典树，其中search可以实现正则表达式中的.功能
这个题重点在正则表达式，如果一个单词中第一个字符为.   那么就用.之后的所有字符和字典中的所有字典树进行匹配

 class WordDictionary(object):

     def __init__(self):
         self.root = {}

     def addWord(self, word):
         cur = self.root
         for c in word:
             cur  = cur.setdefault(c,{})
         cur[None] = None

     def search(self, word):
         def find(word,node):
             if not word:
                 return None in node
             c,w = word[0],word[1:]
             if c != '.':
                 return c in node and find(w,node[c])
             return any(find(w,nd) for nd in node.values() if nd)
         return find(word,self.root)

不明白为什么设置node.is_word会错误。。