Introduction to the method of implementing a simple dictionary tree in Python

The example in this article describes how to implement a simple dictionary tree in Python. Share it with everyone for your reference, the details are as follows:

#coding=utf8
"""代码实现了最简单的字典树，只支持由小写字母组成的字符串。
在此代码基础上扩展一下，就可以实现比较复杂的字典树，比如带统计数的，或支持更多字符的字典树，
或者是支持删除等操作。
"""
class TrieNode(object):
  def __init__(self):
    # 是否构成一个完成的单词
    self.is_word = False
    self.children = [None] * 26
class Trie(object):
  def __init__(self):
    self.root = TrieNode()
  def add(self, s):
    """Add a string to this trie."""
    p = self.root
    n = len(s)
    for i in range(n):
      if p.children[ord(s[i]) - ord('a')] is None:
        new_node = TrieNode()
        if i == n - 1:
          new_node.is_word = True
        p.children[ord(s[i]) - ord('a')] = new_node
        p = new_node
      else:
        p = p.children[ord(s[i]) - ord('a')]
        if i == n - 1:
          p.is_word = True
          return
  def search(self, s):
    """Judge whether s is in this trie."""
    p = self.root
    for c in s:
      p = p.children[ord(c) - ord('a')]
      if p is None:
        return False
    if p.is_word:
      return True
    else:
      return False
if __name__ == '__main__':
  trie = Trie()
  trie.add('str')
  trie.add('acb')
  trie.add('acblde')
  print trie.search('acb')
  print trie.search('ac')
  trie.add('ac')
  print trie.search('ac')

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