python

Question

- 对于这项任务，我们应该使用教授提供的代码创建push_back，pop_back和pop_front方法。

我一直收到错误 “AssertionError：main.LinkedList对象位于0x106ec7dd0＆gt;＆gt;！= 1”

我的猜测是pop和push方法的返回返回对链表中的值的引用，而不是这些节点中保存的实际值。我完全难过了。我问过周围，每个人都说同样的话。你的引用搞砸了，但是我无法弄明白什么是错的以及如何修复它。

非常感谢任何帮助!!!!

此外，如果有人想在这样的问题上推荐初学者论坛，那也将非常感激。我确实已经发布了stackoverflow，但我对任何其他建议持开放态度。

这是源代码。

'''-------------------------------------------- ------------------ '''

'''-----------教练提供的这个区块-----------'''

class LinkedList（object）：

class Node(object):
    # pylint: disable=too-few-public-methods
    ''' no need for get or set, we only access the values inside the
        LinkedList class. and really, never have setters. '''


    def __init__(self, value, next_node):
        self.value = value
        self.next_node = next_node

def __init__(self, initial=None):

    self.front = self.back = self.current = None
    self.next_node = self.current

def empty(self):
    return self.front == self.back == None

def __iter__(self):
    self.current = self.front
    return self

def __next__(self):
    if self.current:
        tmp = self.current.value
        self.current = self.current.next_node
        return tmp
    else:
        raise StopIteration()

def push_front(self, value):
    new = self.Node(value, self.front)
    if self.empty():
        self.front = self.back = new
    if self.empty() is not None:
        self.front = new

''^^^^^^^这个座位由讲师提供^^^^^^^'''

''' I need help with following three methods'''

def pop_front(self):
    if self.empty():
        return None
    tmp = self.front.value
    self.front = self.front.next_node
    if not self.front:
        self.back = None
    return tmp

def push_back(self, value):
    new = self.Node(value, self.back)
    if self.empty():
        self.back = self.front = new
    if self.empty() is not None:
        if self.back.next_node is None:
            self.current = self.back
            self.back.next_node = new


def pop_back(self):
    if self.empty():
        return None
    tmp = self.back.value
    if not self.front.next_node:
        self.front = self.back = None
    else:
        while self.front.next_node is not self.back:
            self.front = self.next_node
        self.front.next_node = None
        self.back = self.front
    return tmp

'''开始测试'''

class TestPrintMethods（unittest.TestCase）：

def test(self):
    linked_list = LinkedList()
    linked_list.push_front(1)
    linked_list.push_front(2)
    linked_list.push_front(3)
    linked_list.pop_front()
    print(linked_list.front.value)
    print(linked_list.back.value)
    print(linked_list)

class TestEmpty（unittest.TestCase）：

def test(self):
    self.assertTrue(LinkedList().empty())

class TestPushFrontPopBack（unittest.TestCase）：

def test(self):
    linked_list = LinkedList()
    linked_list.push_front(1)
    linked_list.push_front(2)
    linked_list.push_front(3)
    self.assertFalse(linked_list.empty())
    self.assertEqual(linked_list.pop_back(), 1)
    self.assertEqual(linked_list.pop_back(), 2)
    self.assertEqual(linked_list.pop_back(), 3)
    self.assertTrue(linked_list.empty())

class TestPushFrontPopFront（unittest.TestCase）：

def test(self):
    linked_list = LinkedList()
    linked_list.push_front(1)
    linked_list.push_front(2)
    linked_list.push_front(3)
    self.assertEqual(linked_list.pop_front, 3)
    self.assertEqual(linked_list.pop_front, 2)
    self.assertEqual(linked_list.pop_front, 1)
    self.assertTrue(linked_list.empty())

class TestPushBackPopFront（unittest.TestCase）：

def test(self):
    linked_list = LinkedList()
    linked_list.push_back(1)
    linked_list.push_back(2)
    linked_list.push_back(3)
    self.assertFalse(linked_list.empty())
    self.assertEqual(linked_list.pop_front, 1)
    self.assertEqual(linked_list.pop_front, 2)
    self.assertEqual(linked_list.pop_front, 3)
    self.assertTrue(linked_list.empty())

class TestPushBackPopBack（unittest.TestCase）：

def test(self):
    linked_list = LinkedList()
    linked_list.push_back(1)
    linked_list.push_back("foo")
    linked_list.push_back([3, 2, 1])
    print(linked_list)
    self.assertFalse(linked_list.empty())
    self.assertEqual(linked_list.pop_back(), [3, 2, 1])
    self.assertEqual(linked_list.pop_back(), "foo")
    self.assertEqual(linked_list.pop_back(), 1)
    self.assertTrue(linked_list.empty())

'''-------------------------------------------- ------------------ '''

Answer 1

您忘记调用这些方法

self.assertEqual(linked_list.pop_front, 1)

应该是

self.assertEqual(linked_list.pop_front(), 1)