1、实现多个任务之间进行切换，yield、greenlet都没有实现检测I/O，greenlet在实现多任务切换下更简单
from greenlet import greenlet
def eat(name):
print(f"{name} eat 1")
g2.switch('egon') # 切换
print(f"{name} eat 2")
g2.switch()
def play(name):
print(f"{name} play 1")
g1.switch()
print(f"{name} play 2")
g1 = greenlet(eat)
g2 = greenlet(play)
g1.switch('egon') # 程序从此处执行 egon eat 1
egon play 1
egon eat 2
egon play 2
2、一个协程遇到IO操作自动切换到其它协程（如何实现检测IO，yield、greenlet都无法实现，就用到了gevent模块（select机制））
2.1 gevent模块
可以轻松的实现并发或异步编程，在gevent中用到的主要模式是Greenlet,
2.1.1、遇到io阻塞时会自动切换任务 --只实现识别gevent可以识别的阻塞
# 遇到io阻塞会自动切换任务
import gevent,time
def eat(name):
print(f"{name} eat1")
gevent.sleep(2) # 模拟io阻塞
print(f"{name} eat2")
def play(name):
print(f"{name} play1")
gevent.sleep(2)
print(f"{name} play2")
start = time.time()
g1 = gevent.spawn(eat,'alex')
g2 = gevent.spawn(play,'alex')
g1.join()
g2.join()
stop = time.time()
print(stop-start) alex eat1
alex play1
alex eat2
alex play2
2.007000207901001
2.1.2、实际情况中的应用gevent 打补丁(monkey.patch_all()) 识别 所有阻塞
alex eat1
alex play1
alex eat2
alex play2
2.005999803543091
3、基于gvent模块实现并发的套接字通信
服务端：
# 基于 gevent
from gevent import monkey;monkey.patch_all()
import socket
import gevent def Server(ip_port):
server = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
server.bind(ip_port)
server.listen(5)
while True:
conn,addr = server.accept()
gevent.spawn(communicate,conn)
server.close()
def communicate(conn):
while True:
try:
data = conn.recv(1024).decode('utf-8')
conn.send(data.upper().encode('utf-8'))
except Exception as e:
print(e)
break
conn.close()
if __name__ == '__main__':
ip_port = ('127.0.0.1',8080)
Server(ip_port)
# g = gevent.spawn(Server,ip_port)
# g.join()
客户端：启动500个线程模拟500个客户端向服务端发消息
import socket
from threading import Thread,currentThread
def client():
client = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
ip_port = ('127.0.0.1',8080)
client.connect(ip_port)
while True:
client.send(f"{currentThread().getName()} hello".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()