用python实现一个不排序的列表功能

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# learn <<Problem Solving with Algorithms and Data Structures>>
# Release 3.0
# chengang882 @ 2016-12-21
# Completed implementation of a Unordered List ADT

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

    def get_data(self):
        return self.data

    def get_next(self):
        return self.next

    def set_data(self, new_data):
        self.data = new_data

    def set_next(self, new_next):
        self.next = new_next

class UnorderedList(object):
    def __init__(self):
        self.head = None

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

    def add(self, item):
        temp = Node(item)
        temp.set_next(self.head)
        self.head = temp

    def size(self):
        current = self.head
        count = 0
        while current != None:
            count += 1
            current = current.get_next()
        return count

    def search(self, item):
        current = self.head
        found = False
        while current != None and not found:
            if  current.get_data() == item:
                found = True
            else:
                current = current.get_next()
        return found

    def remove(self, item):
        current = self.head
        previous = None
        found = False
        while not found:
            if current.get_data() == item:
                found = True
            else:
                previous = current
                current = current.get_next()
        if previous == None:
            self.head = current.get_next()
        else:
            previous.set_next(current.get_next())
    def show(self):
        pass

if __name__ == "__main__":
    ul = UnorderedList()
    print(ul.is_empty())
    ul.add(45)
    ul.add(78)
    ul.add("adfd")
    ul.add("4345")
    ul.add(3)
    print(ul.is_empty())
    print(ul.size())
    print(ul.search(45))
    print(ul.remove(78))
    print(ul)

>>>
True
False
5
True
None
<__main__.UnorderedList object at 0x0000000002F1C860>
>>>