python类对象和变量生命周期

Question

class Node:
    def __init__(self):
        self.data = None # contains the data
        self.next = None # contains the reference to the next node


class linked_list:
    def __init__(self):
        self.cur_node = None
        self.counter = 0


    def add_node(self, data):
        new_node = Node() # create a new node
        new_node.data = data
        new_node.next = self.cur_node # link the new node to the' previous' node.
        self.cur_node = new_node #  set the current node to the new one.

    def list_print(self):
        node = self.cur_node # cant point to ll!
        while node:
            print node.data
            node = node.next




ll = linked_list()

ll.add_node(1)
ll.add_node(2)
ll.add_node(3)
ll.list_print()

1. 我正在创建linked_list类的对象。

2. 之后我调用了成员函数add_node（）三次。

3. 但是当我调用函数list_print时，它会打印3-> 2＆gt; 1.

4. 我的问题是这是怎么打印的？据我说它应该打印＆＃34; 3＆＃34;只因为当我调用ll.list_print（）时，self.cur_node的值等于3.所以如何打印所有三个输入。它在哪里存储以前的值＆＃34; 2,1＆＃34; ？请帮帮我。

Answer 1

在add_note方法中，您在声明最后一个之前将new_node.next =声明为self.cur_node，但是，这是不必要的。评论那条线！我添加了一个打印来检查该方法中的进度

class Node:
    def __init__(self):
        self.data = None # contains the data
        self.next = None # contains the reference to the next node


class linked_list:

    def __init__(self):
        self.cur_node = None
        self.counter = 0

    def add_node(self, data):
        new_node = Node() # create a new node
        new_node.data = data
        #new_node.next = self.cur_node # link the new node to the' previous' node.
        print(self.cur_node)
        self.cur_node = new_node #  set the current node to the new one.

    def list_print(self):
        node = self.cur_node # cant point to ll!
        while node:
            print node.data
            node = node.next

ll = linked_list()
ll.add_node(1)
ll.add_node(2)
ll.add_node(3)
ll.list_print()