基于 根据定义的Node类，以Node为结点定义链表LinkList类，其中包含isEmpty, length, add, append, insert, search, remove, travel 等函数。，实现栈这一数据结构 (包括函数push, pop, top，isEmpty, length）用python

以下是基于Node类实现链表LinkList类的代码，同时实现了栈这一数据结构：

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

class LinkList:
    def __init__(self):
        self.head = None

    def isEmpty(self):
        return self.head == None

    def length(self):
        count = 0
        cur = self.head
        while cur:
            count += 1
            cur = cur.next
        return count

    def add(self, data):
        new_node = Node(data)
        if self.isEmpty():
            self.head = new_node
        else:
            new_node.next = self.head
            self.head = new_node

    def append(self, data):
        new_node = Node(data)
        if self.isEmpty():
            self.head = new_node
        else:
            cur = self.head
            while cur.next:
                cur = cur.next
            cur.next = new_node

    def insert(self, pos, data):
        if pos <= 0:
            self.add(data)
        elif pos >= self.length():
            self.append(data)
        else:
            new_node = Node(data)
            cur = self.head
            count = 0
            while count < (pos - 1):
                count += 1
                cur = cur.next
            new_node.next = cur.next
            cur.next = new_node

    def search(self, data):
        cur = self.head
        while cur:
            if cur.data == data:
                return True
            cur = cur.next
        return False

    def remove(self, data):
        if self.isEmpty():
            return
        if self.head.data == data:
            self.head = self.head.next
            return
        cur = self.head
        while cur.next:
            if cur.next.data == data:
                cur.next = cur.next.next
                return
            cur = cur.next

    def travel(self):
        cur = self.head
        while cur:
            print(cur.data, end=' ')
            cur = cur.next
        print()

class Stack:
    def __init__(self):
        self.linklist = LinkList()

    def push(self, data):
        self.linklist.add(data)

    def pop(self):
        if self.linklist.isEmpty():
            return None
        data = self.linklist.head.data
        self.linklist.head = self.linklist.head.next
        return data

    def top(self):
        if self.linklist.isEmpty():
            return None
        return self.linklist.head.data

    def isEmpty(self):
        return self.linklist.isEmpty()

    def length(self):
        return self.linklist.length()

我们可以通过以下方式测试栈的实现：

s = Stack()

s.push(1)
s.push(2)
s.push(3)

print(s.pop())  # 3
print(s.top())  # 2

s.push(4)

print(s.pop())  # 4

print(s.length())  # 2
print(s.isEmpty())  # False