simple tries implementation

tries.py

#!/bin/python3

class Node(object):
    def __init__(self, key=None, count=0):
        self._key = key
        self._count = count
        self._children = dict()
    
    @property
    def children(self):
        return self._children

    @property
    def key(self):
        return self._key
    
    @property
    def count(self):
        return self._count

    @count.setter
    def count(self, value):
        self._count = value

    def __str__(self):
        return '{}:{}'.format(str(self.key), str(self.count))

    def add_child(self, node, count=0):
        if not isinstance(node, Node):
            key = node # using input as key
            self._children[key] = Node(key, count)
        else:
            self._children[node.key] = node


class Tries(object):
    def __init__(self):
        self._root = Node()
    
    def add(self, word):
        current_node = self._root        
        for i in range(len(word)):
            if word[i] not in current_node.children:
                current_node.add_child(word[i])
            current_node = current_node.children[word[i]]
        current_node.count += 1

    def graph(self, node=None, depth=0):
        if not node:
            node = self._root
            print('_:_')
        if len(node.children) > 0:
            depth += 1
            for key, child in node.children.items():
                print('{}{}'.format('  '* depth, child))                
                self.graph(child, depth)

    def has(self, word):
        current_node = self._root
        for i in range(len(word)):
            if word[i] in current_node.children:
                current_node = current_node.children[word[i]]
            else:
                return False
        return True        

    def count_children(self, node):
        count = [node.count]
        def counter(node):
            for k in node.children:
                count[0] += node.children[k].count
                counter(node.children[k])
        counter(node)
        return count[0]

    def count(self, word):
        count = 0
        current_node = self._root
        for i in range(len(word)):
            if word[i] in current_node.children:
                current_node = current_node.children[word[i]]
            else:
                return 0
        return self.count_children(current_node)

if '__main__' == __name__:
    trie = Tries()
    trie.add('hello')
    trie.add('hellos')
    trie.add('hello')
    trie.add('how')
    trie.add('are')
    trie.add('you')
    trie.add('thank')
    trie.add('thanks')
    trie.add('you')

    trie.graph()

    print(trie.has('hel'))    
    print(trie.has('helo'))
    print(trie.count('hello'))