问题是:

我有一个 trie

在所有trie中,每个节点上的叶子数是可变的,每个值的键实际上是由到达每个叶子所需的路径组成的。

我试图使用生成器遍历树的后序,但我不能让它工作。我做错什么了?

class Node():
    '''Each leaf in the trie is a Node() class'''
    def __init__(self):
        self.children = {}
        self.value = 0

class Trie():
    '''The Trie() holds all nodes and can return a list of their values'''
    def __init__(self):
        self.root = Node()
    def add(self, key, value):
        '''Store a "value" in a position "key"'''
        node = self.root
        for digit in key:
            number = digit
            if number not in node.children:
                node.children[number] = Node()
            node = node.children[number]
        node.value = value
    def __iter__(self):
        return self.postorder(self.root)
    def postorder(self, node):
        if node:
            for child in node.children.values():
                self.postorder(child)
            # Do my printing / job related stuff here
            if node.value > 0:
                yield node.value

示例用法:

>>trie = Trie()
>>trie.add('foo', 3)
>>trie.add('foobar', 5)
>>trie.add('fobaz', 23)

>>for key in trie:
>>....print key
>>
3
5
23

注意:我省略了代码块中的换行符,以便更轻松地复制粘贴。