Question

所以我的老师让我们使用堆栈链表为我的数据结构类实现一个队列。我已经提出了以下代码，我似乎不理解python在运行单元测试时给出的错误......

这是我的代码`

devDependencies

这是我的单元测试用例

node_modules

这是我继续接收我的Pycharm的错误..

class QueueLinked:

    def __init__(self,capacity):
        self.capacity = capacity # a capacity
        self.num_items = 0
        self.front = None
        self.rear = None

    def is_empty(self):     # This function will retrun a bool if the number of items is = to 0
        return self.num_items == 0

    def is_full(self):
        return self.num_items == self.capacity

    def enqueue(self, item):
        if self.num_items == self.capacity:
            raise IndexError('Can\'t  enqueue into full queue.')
        else:
            self.num_items +=1
            temp = Node()  # this creates a temporary node
            oldrear = self.rear
            self.rear =   temp
            oldrear.set_next(self.rear)


    def dequeue(self):
        if self.num_items == 0:  # this will through an exception because if there are no items we cant pop
            raise IndexError('Can\'t dequeue from empty queue.')
        else:
            self.num_items -=1
            oldfront = self.front
            self.front = self.front.get_next()
            return oldfront.get_data()


    def num_in_queue(self):
        return self.num_items


class Node:

    def __init__(self):
        self.next = None  # this initializes a node with next pointing to none

    def set_data(self, data):  # this passes the parameter data to the data portion of the node
        self.data = data  # this constructs that data portion of a node everytime we create a node

    def get_data(self):  # get data from the node that was previous newwest
        return self.data  # returns the data from that node

    def set_next(self, newNext):  # this will set a new next to point as in after the head
        self.next = newNext  # this constructs the next portion of the 2 part portion from the node

    def get_next(self):  # this will retrieve the next value from the node
        return self.next`

我不明白什么？

Answer 1

正如评论中已有人指出的那样，您发布的追溯表示set_data方法中调用了enqueue，而您的代码只会调用set_next。但是我假设您在set_next时遇到了类似的错误。

在QueueLinked中，您使用值self.rear初始化None。在enqueue方法中，您使用oldrear的值初始化变量self.rear，该值enqueue在调用None时仍为oldrear。此时self.rear和None都是set_next。您试图在oldrear上调用None（仍然== None）并收到错误消息，告诉您set_next没有self.rear = Node()方法

我没有查看整个代码，因此我不确定这是否正确，但我认为您可以初始化async function asyncFunctionINeedToCall() { await childAsyncFunction() } asyncFunctionINeedToCall()并且它可以正常工作。

Python的队列链接列表

1 个答案: