python-面向对象、栈的封装

面向对象、栈的封装"/>

python-面向对象、栈的封装

目录

• 1、面向对象
• 2、封装特性
• 3、继承特性
• 4、重写继承类方法
• 5、链表和数组的区别
• 6、多继承
• 7、私有属性私有方法
• 8、多态特性
• 9、栈的封装
• 10、队列的封装
• 11、二叉树的封装

1、面向对象

2、封装特性

实例化对象巩固练习：

class People:def __init__(self, name, age, gender):self.name = nameself.age = ageself.gender = genderdef shopping(self):print(f'{self.name},{self.age}岁,{self.gender},去西安赛格购物广场购物 ')def learning(self):print(f'{self.name},{self.age}岁,{self.gender},在西部开源学习')p1 = People('小明', 18, '男')
p2 = People('小王', 22, '男')
p3 = People('小红', 10, '女')p1.shopping()
p2.shopping()
p3.learning()

3、继承特性

4、重写继承类方法

class Student:"""父类Student"""def __init__(self, name, age):self.name = nameself.age = agedef learning(self):print(f'{self.name}正在学习')def choice_course(self):print('正在选课中'.center(50, '*'))class MathStudent(Student):"""MathStudent的父类是Student"""def choice_course(self):# 需求: 先执行父类的choice_course方法， 在个性化执行自己的方法。# Student.choice_course(self)  # 解决方法1: 直接执行父类的方法，但不建议# 解决方法2： 通过super找到父类，再执行方法(建议且生产环境代码常用的方式)super(MathStudent, self).choice_course()info = """课程表1. 高等数学2. 线性代数3. 概率论"""print(info)# 实例化
m1 = MathStudent("粉条博士", 8)
m1.choice_course()s1 = Student("粉条博士", 8)
s1.choice_course()

5、链表和数组的区别

数组增加

数组删除
数组修改

链表增加

链表删除

链表查看修改需要遍历

封装练习题

第一步：封装

#封装节点类
class listNode:def __init__(self,val=None,next=None):self.val=valself.next=nextdef travel(self,head):while head.next:print(head.next.val,end=',')head = head.nextdef create_l1():#l1 = 2,4,3#l2 = 5,6,4l1 = listNode()node1 = listNode(val=2)node2 = listNode(val=4)node3 = listNode(val=3)l1.next = node1node1.next = node2node2.next = node3return l1def create_l2():l2 = listNode()node1 = listNode(val=5)node2 = listNode(val=6)node3 = listNode(val=4)l2.next = node1node1.next = node2node2.next = node3return l2l1 = create_l1()
l2 = create_l2()l1.travel(l1)
print()
l1.travel(l2)

# 封装节点类
class ListNode:def __init__(self, val=0, next=None):self.val = valself.next = nextdef travel(self, head):"""遍历链表里面的每一个元素"""while head:print(head.val, end=',')head = head.nextdef create_l1():# l1 = 2,4,3# l2 = 5, 6, 4l1 = ListNode()node1 = ListNode(val=2)node2 = ListNode(val=4)node3 = ListNode(val=3)l1.next = node1node1.next = node2node2.next = node3return  l1.nextdef create_l2():# l1 = 2,4,3# l2 = 5, 6, 4l2 = ListNode()node1 = ListNode(val=5)node2 = ListNode(val=6)node3 = ListNode(val=4)l2.next = node1node1.next = node2node2.next = node3return  l2.nextdef addTwoNumbers(l1: ListNode, l2: ListNode) -> ListNode:res = 0l3 = ListNode()cur = l3while(l1 or l2):if(l1):res += l1.val  # res=2l1 = l1.nextif(l2):res += l2.val # res=2+5=7l2 = l2.next# res=10, val=0, res=>val val=res%10# res=14, val=4, 14%10=4l3.next = ListNode(res%10)l3 = l3.next# res=10, 进位为1， 10//10=1# res=14, 进位为1， 14//10=1res  //= 10if res == 1:l3.next = ListNode(1)return cur.next# 中午留个作业:查一下它的功能
if __name__ == '__main__':l1 = create_l1()l2 = create_l2()l3 = addTwoNumbers(l1, l2)l3.travel(l3)

练习题二：

6、多继承

a找b 如果b没有找c（先找同一层的）再找d

7、私有属性私有方法

类的外部不能访问和操作如下：

类的内部可以访问：


私有方法是以双下划线开头得，可以在类的内部访问，不能在类的外部访问

可以在类的内部访问

结果得出120

报错！！ 类的外部包括子类也不能运行

8、多态特性

不同的对象调用同一个方法时结果是不同的，就叫做多态

9、栈的封装

栈的封装

class Stack(object):"""栈的封装[1, 2, 3, 4]"""def __init__(self):self.stack = []def push(self, value):"""入栈"""self.stack.append(value)print(f"入栈元素为{value}")def pop(self):"""出栈"""if self.is_empty():raise  Exception("栈为空")item = self.stack.pop()print(f"出栈元素为{item}")return  itemdef is_empty(self):"""判断栈是否为空"""return  len(self.stack) == 0def top(self):"""返回栈顶元素"""if self.is_empty():raise  Exception("栈为空")return  self.stack[-1]def __len__(self):"""魔术方法, len(object)自动执行的方法"""return  len(self.stack)if __name__ == '__main__':stack = Stack()stack.push(1)stack.push(2)stack.push(3)print(len(stack))  # 3stack.pop()print(stack.is_empty()) # Falseprint(stack.top())  # 2

10、队列的封装

class Queue(object):"""队列的封装1. 列表的左侧队尾2. 列表的右侧队头"""def __init__(self):self.queue = []def enqueue(self, value):"""入队"""self.queue.insert(0, value)print("入队元素为:", value)def dequeue(self):"""出队"""if self.is_empty():raise  Exception("队列为空")item = self.queue.pop()print("出队元素:", item)return  itemdef __len__(self):"""获取队列的长度"""return  len(self.queue)def first(self):"""获取队头元素"""if self.is_empty():raise Exception("队列为空")return  self.queue[-1]def last(self):"""获取队尾元素"""if self.is_empty():raise Exception("队列为空")return  self.queue[0]def is_empty(self):"""判断队列是否为空"""return  len(self.queue) == 0if __name__ == '__main__':queue = Queue()queue.enqueue(1)queue.enqueue(2)queue.enqueue(3)print(queue.is_empty()) # Falsequeue.dequeue()  # 1出队， 队列只剩32print(queue.first())  # 2print(queue.last())  # 3

11、二叉树的封装

left：左子树 right：右子树

"""
二叉树:.html
"""class Node(object):"""节点类"""def __init__(self, val=None, left=None, right=None):self.val = valself.left = leftself.right = rightclass BinaryTree(object):"""封装二叉树"""def __init__(self, root):self.root = rootdef pre_travel(self, root):"""先序遍历: 根左右"""if (root != None):print(root.val)self.pre_travel(root.left)self.pre_travel(root.right)def in_travel(self, root):"""中序遍历: 左根右"""if (root != None):self.in_travel(root.left)print(root.val)self.in_travel(root.right)def last_travel(self, root):"""后序遍历: 左右根"""if (root != None):self.last_travel(root.left)self.last_travel(root.right)print(root.val)if __name__ == '__main__':node1 = Node(1)node2 = Node(2)node3 = Node(3)node4 = Node(4)node5 = Node(5)node6 = Node(6)node7 = Node(7)node8 = Node(8)node9 = Node(9)node10 = Node(10)bt = BinaryTree(root=node1)node1.left = node2node1.right = node3node2.left = node4node2.right= node5node3.left = node6node3.right = node7node4.left = node8node4.right = node9node5.left = node10# 先序遍历bt.pre_travel(node1)