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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属性查找绑定方法对象之间的交互面向对象的三大特性元类反射网络编程网络的概念五层网络协议socket编写tcp的客户端和服务端socket编写udp的客户端和服务端tcp和udp的特点
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
- 物理层:01010101
- 数据链路层:做分组,数据报/数据帧,mac地址
- 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
- 运输层:tcp/udp,三次握手,四次挥手,可靠传输
- 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
# 服务端
import socket
#生成一个socket对象
soc=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
#绑定地址跟端口号
soc.bind(('127.0.0.1',8001))
#监听(半连接池的大小),不是连接数
soc.listen(3)
#等着客户端来连接,conn相当于连接通道,addr是客户端的地址
while True:
print('等待客户端连接')
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
print('有个客户端连接上了',addr)
while True:
try:
#windows如果客户端断开,会报错,加了try
#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
#等待接收,最大收取1024个字节
data=conn.recv(1024) #会卡主,当客户端有数据过来,才会执行
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)
break
print(data)
except Exception:
break
# 关闭通道
conn.close()
# 关闭套接字
soc.close()
xxxxxxxxxx
# 客户端
import socket
soc=socket.socket()
soc.connect(('127.0.0.1',8001))
while True:
in_s=input('请输入要发送的数据:')
#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
#把b格式转成字符串
ss=str(b'hello',encoding='utf-8')
ss=b'hello'.decode('utf-8')
# #把字符串转成b格式
by=bytes('hello',encoding='utf-8')
by='hello'.encode('utf-8')
soc.send(in_s.encode('utf-8'))
socket编写udp的客户端和服务端
xxxxxxxxxx
import socket
# UDP客户端
client = socket.socket(type=socket.SOCK_DGRAM)
# 直接发
while True:
msg = input('>>:')
client.sendto(msg.encode('utf-8'), ('127.0.0.1', 8003))
data = client.recvfrom(1024)
print(data)
xxxxxxxxxx
import socket
# UDP服务端
server = socket.socket(type=socket.SOCK_DGRAM)
server.bind(('127.0.0.1', 8003))
# udp不需要建立连接,直接发送
# 不需要监听,所以收发方式和tcp不一样
# data = server.recvfrom(1024)
# 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
while True:
data, addr = server.recvfrom(1024)
print(data)
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.