1 yiled可以保存状态，yield的状态保存与操作系统的保存线程状态很像，但是yield是代码级别控制的，更轻量级
2 send可以把一个函数的结果传给另外一个函数，以此实现单线程内程序之间的切换

1. python的线程属于内核级别的，即由操作系统控制调度（如单线程遇到io或执行时间过长就会被迫交出cpu执行权限，切换其他线程运行）
2. 单线程内开启协程，一旦遇到io，就会从应用程序级别（而非操作系统）控制切换，以此来提升效率（！！！非io操作的切换与效率无关）

#并发执行
import time
def producer():g=consumer()next(g)for i in range(10000000):g.send(i)def consumer():while True:res=yield
start_time=time.time()
producer()
stop_time=time.time()
print(stop_time-start_time)  #计算的时间+切换的时间  效率低#串行
import time
def producer():res=[]for i in range(10000000):res.append(i)return resdef consumer(res):passstart_time=time.time()
res=producer()
consumer(res)
stop_time=time.time()
print(stop_time-start_time)  #没有切换的时间了
打印：
1.8201038837432861
1.897108793258667

from greenlet import greenlet
import time
def eat(name):print('%s eat 1' %name)time.sleep(10)g2.switch('egon') #第一次启动print('%s eat 2' %name)g2.switch() #再切def play(name):print('%s play 1' %name )g1.switch()  #再切回来print('%s play 2' %name )
g1=greenlet(eat)
g2=greenlet(play)g1.switch('egon') #第一次启动的时候传个参数打印：
egon eat 1
egon play 1
egon eat 2
egon play 2

from gevent import monkey;monkey.patch_all() #把下面所有的涉及I/O操作的给你打了个标记，被gevent识别
import gevent
import timedef eat(name):print('%s eat 1' % name)time.sleep(3) #遇到I/O立马切换到下面执行print('%s eat 2' % name)def play(name):print('%s play 1' % name)time.sleep(4)print('%s play 2' % name)start_time=time.time()
g1=gevent.spawn(eat,'egon') #异步提交的方式
g2=gevent.spawn(play,'alex')g1.join() #等待执行完
g2.join()
stop_time=time.time()
print(stop_time-start_time)打印：
egon eat 1
alex play 1
egon eat 2
alex play 2
4.0012288093566895

from gevent import monkey;monkey.patch_all()
import gevent
import timedef eat(name):print('%s eat 1' % name)time.sleep(3)print('%s eat 2' % name)def play(name):print('%s play 1' % name)time.sleep(4)print('%s play 2' % name)g1=gevent.spawn(eat,'egon')
g2=gevent.spawn(play,'alex')# time.sleep(5)# g1.join()
# g2.join()gevent.joinall([g1,g2]) #相当于上边两行代码打印：
egon eat 1
alex play 1
egon eat 2
alex play 2

#基于gevent实现
from gevent import monkey,spawn;monkey.patch_all()
from socket import *def communicate(conn):while True:try:data=conn.recv(1024)if not data:breakconn.send(data.upper())except ConnectionResetError:breakconn.close()def server(ip,port):server = socket(AF_INET, SOCK_STREAM)server.bind((ip,port))server.listen(5)while True:conn, addr = server.accept()spawn(communicate,conn) #造一个协程对象，提交完这个对象它不会执行server.close()if __name__ == '__main__':g=spawn(server,'127.0.0.1',8090)g.join()

##客户端from socket import *
from threading import Thread,currentThreaddef client():client=socket(AF_INET,SOCK_STREAM)client.connect(('127.0.0.1',8090))while True:client.send(('%s hello' %currentThread().getName()).encode('utf-8'))data=client.recv(1024)print(data.decode('utf-8'))client.close()
if __name__ == '__main__':for i in range(500):t=Thread(target=client)t.start()