添加整个. py文件如果您运行它应该可以工作

from collections import deque

class BinaryTree:
    def __init__(self, data, left = None, right = None):
        self.key = data
        self.left = left
        self.right  = right

    def insert_left(self, data):
        self.left = BinaryTree(data, left=self.left)  

    def insert_right(self, data):
        self.right = BinaryTree(data, right=self.right)

    def get_left_subtree(self):
        return self.left

    def get_right_subtree(self):
        return self.right

    def set_value(self, val):
        self.key = val

    def get_value(self):
        return self.key

    def create_string(self, indent):
        string = str(self.key) + '---+'
        if self.left:
            string += '\n(l)' + indent + self.left.create_string(indent + '    ')
        if self.right:
            string += '\n(r)' + indent + self.right.create_string(indent + '    ')
        return string

    def __str__(self):
        return self.create_string('  ')

    def return_list(self, templist):
        templist.append(self.key)
        if self.left is None:
            templist.append(None)
        else:
            self.left.return_list(templist)
        if self.right is None:
            templist.append(None)
        else:
            self.right.return_list(templist)


def return_b_list(tree,templist,queue):
    if tree is None:
        return;
    queue.append(tree)
    while len(queue) !=0:
        node = queue.popleft()
        if node is None:
            templist.append(None)
        else:
            templist.append(node.key)
            queue.append(node.left)
            queue.append(node.right)




def main():    
    tree = BinaryTree(3) 
    tree.insert_left(29)
    tree.insert_right(4)
    right = tree.get_right_subtree()
    left = tree.get_left_subtree()
    left.insert_left(26)
    right.insert_right(2)
    right2 = right.get_right_subtree()
    right2.insert_left(9)
    templist = []
    queue = deque() # you should do a from collections import deque
    return_b_list(tree,templist,queue)
    print tree.create_string(' ')
    print templist

main()

您应该向此函数传递一个空列表

def return_list(self, templist):
    templist.append(self.key)
    if self.left is None:
        templist.append(None)
    else:
        self.left.return_list(templist)
    if self.right is None:
        templist.append(None)
    else:
        self.right.return_list(templist)

调用此方法后，templist 将具有所需的列表

如果您确实在寻找广度优先搜索，那么此方法可能会有所帮助

  def return_b_list(tree,templist,queue):
    if tree is None:
        return;
    queue.append(tree)
    while len(queue) !=0:
        node = queue.popleft()
        if node is None:
            templist.append(None)
        else:
            templist.append(node.key)
            queue.append(node.left)
            queue.append(node.right)

如何打电话？（此方法不必是类的一部分）

def main():    
    tree = BinaryTree(3) 
    tree.insert_left(29)
    tree.insert_right(4)
    right = tree.get_right_subtree()
    left = tree.get_left_subtree()
    left.insert_left(26)
    right.insert_right(2)
    right2 = right.get_right_subtree()
    right2.insert_left(9)
    templist = []
    queue = deque() # you should do a from collections import deque
    return_b_list(tree,templist,queue)
    print templist