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Python学习day34-面向对象和网络编程总结

面向对象及高阶

类与对象

类:是一系列共同的属性和方法

对象:是属性和方法的结合体

属性查找

包括数据属性和方法.

数据属性:对象中找-->类中-->父类(按照__mro__查找,Python2中没有mro列表)-->obj-->报错 方法查找:对象的绑定方法-->类中-->父类(按照__mro__查找,Python2中没有mro列表)-->obj-->报错

绑定方法

定义在类内部的没有被任何装饰器装饰的函数,就是方法 给对象用的,对象.方法(默认把自身作为第一个参数传过去) 类来调用,就是普通函数,有几个值就传几个值

对象之间的交互

把一个对象传到另一个对象中,从而操作这个对象

面向对象的三大特性

-继承:
-在类名后的括号中写要继承的类,用逗号分隔
-python中支持多继承,java只支持单继承(属性查找顺序)
-新式类和经典类:
-继承了object的类都叫新式类,Python3中都是新式类
-Python2中才有新式类和经典类的区别
-菱形问题的查找:
-广度优先:新式类
-深度优先:经典类
-mro列表
-super() 特殊的对象,调用父类的方法和属性,严格按照mro列表找的
-self和super的区别,self一定是从根部开始找,super()从当前位置按照mro列表找
-类名.方法() 指名道姓的调用类和方法,就是个普通函数
-派生:子类多出来的属性和方法-多态和多态性:
-一个事物多种形态
-多态性:执行同一个事物的同一个方法,表现出来的结果是不一样的
-两种约束子类必须实现一定方法的方式
-abc模块
-raise抛异常
-鸭子类型:走路像鸭子,叫声像鸭子,你就是鸭子
-len()内部是调用了对象.len()
-封装:
-把属性或方法隐藏起来
-以__开头,就会隐藏
-但并没有实际的隐藏,只是做了一个变形
-隐藏属性,保证数据安全
-隐藏方法,隔离复杂度
-property 装饰器,包装方法成数据属性
-其他两个装饰器:
-classmethod,类的绑定方法,可以类来调用,会自动把类本身传入,对象也可以调用
-staticmethod,静态方法,都可以调用,不会自动传参,就是普通函数

元类

__call__
-__new__
-__getattr__
-__setattr__
-__delattr__
-type和object

反射

(通过字符串去获取,删除,修改对象的属性或方法)

-hasattr

-getattr

-setattr

-delattr

-isinstance 和 issubclass

网络编程

网络的概念

网络最简单的来说就是链接介质+协议.

五层网络协议

  1. 物理层:01010101
  2. 数据链路层:做分组,数据报/数据帧,mac地址
  3. 网络层:IP地址,通过IP得到mac地址,用arp协议,用于mac地址的学习
  4. 运输层:tcp/udp,三次握手,四次挥手,可靠传输
  5. 应用层:写的程序都是应用层,基于socket写的,或者是http协议,以及邮件协议

socket编写tcp的客户端和服务端

 
 
 
xxxxxxxxxx
1
30
 
 
 
 
1
# 服务端
2
import socket
3
#生成一个socket对象
4
soc=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
5
#绑定地址跟端口号
6
soc.bind(('127.0.0.1',8001))
7
#监听(半连接池的大小),不是连接数
8
soc.listen(3)
9
#等着客户端来连接,conn相当于连接通道,addr是客户端的地址
10
while True:
11
    print('等待客户端连接')
12
    conn,addr=soc.accept()    #卡主,如果没有客户端连接,会一直卡在这,当有连接,才继续往下走
13
    print('有个客户端连接上了',addr)
14
    while True:
15
        try:
16
            #windows如果客户端断开,会报错,加了try
17
            #linux如果客户端,断开,不会报错,会收到空,所有当data为空时,也break
18
            #等待接收,最大收取1024个字节
19
            data=conn.recv(1024)    #会卡主,当客户端有数据过来,才会执行
20
            if len(data)==0:  #处理linux客户端断开,如果在window下这段代码根本不会执行(即便是客服端发了空,这个地方也不会走到)
21
                break
22
            print(data)
23
        except Exception:
24
​
25
            break
26
    # 关闭通道
27
    conn.close()
28
​
29
​
30
# 关闭套接字
31
soc.close()
 
 
 
 
 
xxxxxxxxxx
1
18
 
 
1
# 客户端
2
import socket
3
​
4
soc=socket.socket()
5
​
6
soc.connect(('127.0.0.1',8001))
7
while True:
8
    in_s=input('请输入要发送的数据:')
9
    #发送的数据必须是b格式,in_s.encode('utf-8')  把字符串编码成b格式
10
    #把b格式转成字符串
11
    ss=str(b'hello',encoding='utf-8')
12
    ss=b'hello'.decode('utf-8')
13
    # #把字符串转成b格式
14
    by=bytes('hello',encoding='utf-8')
 
 
15
    by='hello'.encode('utf-8')
16
​
17
​
18
    soc.send(in_s.encode('utf-8'))
19
​
 
 

socket编写udp的客户端和服务端

 
 
 
xxxxxxxxxx
1
14
 
 
 
 
1
import socket
2
​
3
# UDP客户端
4
​
5
client = socket.socket(type=socket.SOCK_DGRAM)
6
​
7
# 直接发
8
while True:
9
msg = input('>>:')
10
client.sendto(msg.encode('utf-8'), ('127.0.0.1', 8003))
11
​
12
data = client.recvfrom(1024)
13
print(data)
14
​
 
 
 
 
 
xxxxxxxxxx
1
17
 
 
 
 
1
import socket
2
​
3
# UDP服务端
4
​
5
server = socket.socket(type=socket.SOCK_DGRAM)
6
​
7
server.bind(('127.0.0.1', 8003))
8
​
9
# udp不需要建立连接,直接发送
10
# 不需要监听,所以收发方式和tcp不一样
11
# data = server.recvfrom(1024)
12
# data是个元组,第一个参数是接收到数据,第二个是客户端的地址端口
13
while True:
14
data, addr = server.recvfrom(1024)
15
​
16
print(data)
17
server.sendto(data, addr)
 
 

tcp和udp的特点

TCP需要建立链接,且传输有保证,为可靠链接.

UDP不需要建立链接,知道地址就可以直接发送,且不需要监听,所以收发方式比tcp更简单,但是不可靠链接,因为互相无法确认是否收到了数据.

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