Day10 网络编程（续）

作用域

Python的作用域是函数，没有块级作用域

if 1 == 1:
    name = 'wang'

print(name)

#wang

for i in range(10):
    name = i

print(name)

#9

def func():
    name = 'wang'

func()
print(name)

#NameError: name 'name' is not defined

name = 'wang'

def f1():
    name = 'snow'
    print(name)

f1()

#snow

作用域链

name = 'wang'
def f1():
    name = 'a'
    def f2():
        name = 'b'
        print(name)
    f2()
f1()

#b

name = 'wang'
def f1():
    print(name)

def f2():
    name = 'snow'
    f1()

f2()

#wang

在函数未执行之前，作用域已经确定

name = 'wang'
def f1():
    print(name)

def f2():
    name = 'snow'
    return f1

ret = f2()
ret()

#wang

li = [x+100 for x in range(10) if x > 5]
print(li)

#[106, 107, 108, 109]

def f1():
    return 1
#相当于
li = [lambda :1]

面试题

li = [lambda :x for x in range(10)]
#li为列表
#li列表中的元素：【函数，函数，函数...】
#函数在没有执行前，内部代码不执行
#列表的第一个元素li[0]是函数
#函数()执行
#li[0]()返回值为9
ret = li[0]()
print(ret)

#9

li = []

for i in range(10):
    def f1():
        return i

    li.append(f1)

ret1 = li[0]()
ret2 = li[1]()
ret3 = li[2]()
ret4 = li[3]()
ret5 = li[4]()
ret6 = li[5]()
ret7 = li[6]()
print(ret1)
print(ret2)
print(ret3)
print(ret4)
print(ret5)
print(ret6)
print(ret7)

#9
#9

#9

#9

#9

#9

#9

只要执行了，就能拿到值

li = []

for i in range(10):
    def f1(x = i):
        return x
    li.append(f1)

print(li[0]())
print(li[1]())
print(li[2]())
print(li[3]())

#0

#1

#2

#3

Python3.x中类默认继承object，Python2.7中类不默认继承object；Python2.7中不继承object的类叫经典类，继承的时候一条道走到黑，继承object的类叫新式类，继承的时候与Python3一致。

IO多路复用实现并发

概述：select、poll、epoll

目的：监听socket对象的内部是否变化？

什么时候变化？连接或收发消息的时候。

sk：服务器端接收客户端的连接，并创建conn对象

conn：要收”发”消息了

简单的IO多路复用

server.py

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

import socket
import select

sk = socket.socket()
sk.bind(('127.0.0.1', 9990,))
sk.listen(5)

while True:
    rlist, w, e = select.select([sk,], [], [], 1)
    print(rlist)
    #rlist中获取的就是socket对象列表,[sk,]
    for r in rlist:
        print(r)
        conn, addr = r.accept()
        conn.sendall(bytes('hello', encoding='utf-8'))

client.py

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

import socket

sk = socket.socket()
sk.connect(('127.0.0.1', 9990,))
data = sk.recv(1024)
print(data)
while True:
    input('>>>')
sk.close()

IO多路复用实现伪并发

server.py

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

import socket
import select

sk = socket.socket()
sk.bind(('127.0.0.1', 9999,))
sk.listen(5)
inputs = [sk,]
while True:
    rlist, w, e = select.select(inputs, [], [], 1)
    #len(inputs)：监听了几个对象,len(rlist)：几个对象发生了变化
    print(len(inputs), len(rlist))
    #rlist中获取的就是socket对象列表,[sk,]
    #rlist = [sk,]
    #rlist = [xiaoming,]
    #rlist = [xiaozhu, xiaogou,]
    for r in rlist:
        if r == 'sk':
            #新客户端来连接
            conn, addr = r.accept()
            # conn是socket对象
            inputs.append(conn)
            conn.sendall(bytes('hello', encoding='utf-8'))
        else:
            #有人（r）给我发消息了
            r.recv(1024)

client.py

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

import socket

sk = socket.socket()
sk.connect(('127.0.0.1', 9999,))
data = sk.recv(1024)
print(data)
while True:
    inp= input('>>>')
    sk.sendall(bytes(inp, encoding='utf-8'))
sk.close()

简单的读写分离

server.py

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

import socket
import select

sk = socket.socket()
sk.bind(('127.0.0.1', 9999,))
sk.listen(5)
inputs = [sk,]
outputs = []
while True:
    rlist, wlist, e = select.select(inputs, outputs, [], 1)
    #len(inputs)：监听了几个对象,len(rlist)：几个对象发生了变化
    print(len(inputs), len(rlist), len(outputs))
    #rlist中获取的就是socket对象列表,[sk,]
    #rlist = [sk,]
    #rlist = [xiaoming,]
    #rlist = [xiaozhu, xiaogou,]
    for r in rlist:
        if r == 'sk':
            #新客户端来连接
            conn, addr = r.accept()
            # conn是socket对象
            inputs.append(conn)
            conn.sendall(bytes('hello', encoding='utf-8'))
        else:
            #有人（r）给我发消息了
            print('==========')
            try:
                ret = r.recv(1024)
                #r.sendall(ret)
                if not ret:
                    raise Exception('断开连接')
                else:
                    outputs.append(r)
            except Exception as e:
                inputs.remove(r)
    for w in wlist:
        #所有给我发过消息的人
        w.sendall(bytes('respones', encoding='utf-8'))
        outputs.remove(w)

client.py

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

import socket

sk = socket.socket()
sk.connect(('127.0.0.1', 9999,))
data = sk.recv(1024)
print(data)
while True:
    inp= input('>>>')
    sk.sendall(bytes(inp, encoding='utf-8'))

sk.close()

IO多路复用增强版

server.py

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

import socket
import select

sk = socket.socket()
sk.bind(('127.0.0.1', 9999,))
sk.listen(5)
inputs = [sk,]
outputs = []
messages = {}
"""
messages = {
    xiaoming:[消息1, 消息2]
    xiaozhu:[消息1, 消息2]
    }
"""
while True:
    rlist, wlist, errorlist = select.select(inputs, outputs, [], 1)
    #len(inputs)：监听了几个对象,len(rlist)：几个对象发生了变化
    print(len(inputs), len(rlist), len(outputs))
    #rlist中获取的就是socket对象列表,[sk,]
    #rlist = [sk,]
    #rlist = [xiaoming,]
    #rlist = [xiaozhu, xiaogou,]
    for r in rlist:
        if r == 'sk':
            #新客户端来连接
            conn, addr = r.accept()
            # conn是socket对象
            inputs.append(conn)
            messages[conn] = []
            conn.sendall(bytes('hello', encoding='utf-8'))
        else:
            #有人（r）给我发消息了
            print('==========')
            try:
                ret = r.recv(1024)
                #r.sendall(ret)
                if not ret:
                    raise Exception('断开连接')
                else:
                    outputs.append(r)
                    messages[r].append(ret)
            except Exception as e:
                inputs.remove(r)
                del messages[r]
    for w in wlist:
        #所有给我发过消息的人
        msg = messages[w].pop()
        resp = msg + bytes('respones', encoding='utf-8')
        w.sendall(resp)
        outputs.remove(w)

client.py

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

import socket

sk = socket.socket()
sk.connect(('127.0.0.1', 9999,))
data = sk.recv(1024)
print(data)
while True:
    inp= input('>>>')
    sk.sendall(bytes(inp, encoding='utf-8'))

sk.close()

select:支持跨平台，底层通过for循环实现，效率不高，监听有个数(1024)限制。

poll:linux使用，内部for循环实现，效率不高，监听个数没有限制。

epoll：内部不在通过for循环，socket对象谁变化谁通知，nginx通过epoll实现，效率高。

IO多路复用不仅仅支持socket对象，只要是IO操作都支持。