为什么我会收到属性在我的类中不存在的错误？

Question

我正在做一个二叉搜索树的类，当我运行我的插入方法时，出现了这个错误：

AttributeError: 'BSearch_tree' object has no attribute 'key'

我不明白我哪里出错了，也不知道该怎么修复！

这是我的代码：

class Tree_node():
    def __init__(self, key, val):
        self.key = key
        self.val = val
        self.left = None
        self.right = None

class BSearch_tree():
    def __init__(self):
        self.root=None

    def insert(self, key, val): 
        if self.root is None:
            self.root=Tree_node(key,val)
        elif key == self.root.key:
            self.val=val
        elif key < self.root.key:
            left = BSearch_tree()
            left.root = self.root.left
            self.root.left=BSearch_tree.insert(left,key,val) 

        elif key > self.root.key:
            right = BSearch_tree()
            right.root=self.root.right
            self.root.right=BSearch_tree.insert(right,key,val)
        return self

Answer 1

我希望我说得对；）

我建议你不用太在意 Tree_Node，直接使用 BSearch_Tree，像这样：

import pprint

class BSearch_tree():
    def __init__(self, key=None, val=None, root=None):
        self.root = root
        self.key = key
        self.val = val
        self.left = None
        self.right = None

    def insert(self, key, val): 
        if self.key is None:
            self.root = self
            self.key = key
            self.val = val
        elif key == self.key:
            self.val=val
        elif key < self.key:
            if self.left == None:
                self.left=BSearch_tree(key,val,self.root)
            self.left.insert(key,val) 
        elif key > self.key:
            if self.right == None:
                self.right=BSearch_tree(key,val,self.root)
            self.right.insert(key,val) 
        # return self

    def __repr__(self):
        return '<BSearch_tree: key: "%s", val: "%s", left: "%s", right: "%s" >' % self.key, self.val, self.left, self.right)

    # lazy retrieval with recursion
    def __getitem__(self, key):
        if self.key is None:
            raise KeyError
        elif key == self.key:
            return self.val
        elif key < self.key:
            if self.left == None:
                raise KeyError
            return self.left[key]

        elif key > self.key:
            if self.right == None:
                raise KeyError
            return self.right[key]

bt = BSearch_tree()
bt.insert(1,'1')
print bt[1]
bt.insert(2,'2')
print bt[2]
try:
    print bt[3]
except KeyError:
    print '3 not there as expected'

bt.insert(5,'5')
print bt[5]
bt.insert(3,'3')
print bt[3]
pprint.pprint(bt)

我有种感觉，应该在某个地方用到 self.root，但现在我不是很确定。