标签：__ spawn 编程并发 Gevent gevent time print import

Gevent的介绍

greenlet已经实现了协程，但是这个还要人工切换，这里介绍一个比greenlet更强大而且能够自动切换任务的第三方库，那就是gevent。

gevent内部封装的greenlet，其原理是当一个greenlet遇到IO操作时，，比如访问网络，就自动切换到其他的greenlet，等到IO操作完成，再在适当的时候切换回来继续执行。

由于IO操作非常耗时，经常是程序处于等待状态，有了gevent为我们自动切换协程，就保证总有greenlet在运行，而不是等待IO。

安装

pip install gevent

Gevent的使用

代码示例：

import gevent


def work(n):
    for i in range(n):
        # 获取当前协程
        print(gevent.getcurrent(), i)
	return 'ok'

g1 = gevent.spawn(work, 5)
g2 = gevent.spawn(work, 5)
g3 = gevent.spawn(work, 5)
g1.join()
g2.join()
g3.join()
# 或者上述三步合作一步：gevent.joinall([g1,g2,g3])
# 拿到work的返回值
result = g1.value

print(result)
# ok

结果：

<Greenlet at 0x16be40925c0: work(5)> 0
<Greenlet at 0x16be40925c0: work(5)> 1
<Greenlet at 0x16be40925c0: work(5)> 2
<Greenlet at 0x16be40925c0: work(5)> 3
<Greenlet at 0x16be40925c0: work(5)> 4
<Greenlet at 0x16be44609a0: work(5)> 0
<Greenlet at 0x16be44609a0: work(5)> 1
<Greenlet at 0x16be44609a0: work(5)> 2
<Greenlet at 0x16be44609a0: work(5)> 3
<Greenlet at 0x16be44609a0: work(5)> 4
<Greenlet at 0x16be4460860: work(5)> 0
<Greenlet at 0x16be4460860: work(5)> 1
<Greenlet at 0x16be4460860: work(5)> 2
<Greenlet at 0x16be4460860: work(5)> 3
<Greenlet at 0x16be4460860: work(5)> 4

可以看到，3个greenlet是依次运行而不是交替运行

Gevent切换执行

遇到IO阻塞时会自动切换任务

import gevent

def work(n):
    for i in range(n):
        # 获取当前协程
        print(gevent.getcurrent(), i)
        #用来模拟一个耗时操作，注意不是time模块中的sleep
        gevent.sleep(1)

g1 = gevent.spawn(work, 5)
g2 = gevent.spawn(work, 5)
g3 = gevent.spawn(work, 5)
g1.join()
g2.join()
g3.join()

结果：

<Greenlet at 0x7fa70ffa1c30: f(5)> 0
<Greenlet at 0x7fa70ffa1870: f(5)> 0
<Greenlet at 0x7fa70ffa1eb0: f(5)> 0
<Greenlet at 0x7fa70ffa1c30: f(5)> 1
<Greenlet at 0x7fa70ffa1870: f(5)> 1
<Greenlet at 0x7fa70ffa1eb0: f(5)> 1
<Greenlet at 0x7fa70ffa1c30: f(5)> 2
<Greenlet at 0x7fa70ffa1870: f(5)> 2
<Greenlet at 0x7fa70ffa1eb0: f(5)> 2
<Greenlet at 0x7fa70ffa1c30: f(5)> 3
<Greenlet at 0x7fa70ffa1870: f(5)> 3
<Greenlet at 0x7fa70ffa1eb0: f(5)> 3
<Greenlet at 0x7fa70ffa1c30: f(5)> 4
<Greenlet at 0x7fa70ffa1870: f(5)> 4
<Greenlet at 0x7fa70ffa1eb0: f(5)> 4

猴子补丁（兼容其他IO）

而time.sleep(2)或其他的阻塞,gevent是不能直接识别的需要用下面一行代码,打补丁,就可以识别了。

from gevent import monkey;monkey.patch_all()必须放到被打补丁者的前面，如time，socket模块之前，或者我们干脆记忆成：要用gevent，需要将from gevent import monkey; monkey.patch_all()放到文件的开头。

from gevent import monkey

monkey.patch_all() # # 打补丁，让gevent框架识别耗时操作，比如：time.sleep，网络请求延时

import threading
import gevent
import time


def work(n):
    for i in range(n):
        # 获取当前协程
        print(gevent.getcurrent(), i)
        print(threading.current_thread())
        # 用来模拟一个耗时操作，注意不是time模块中的sleep
        time.sleep(1)


if __name__ == '__main__':
    g1 = gevent.spawn(work, 3)
    g2 = gevent.spawn(work, 3)
    g3 = gevent.spawn(work, 3)
    g1.join()
    g2.join()
    g3.join()
    print(threading.current_thread())

结果：

<Greenlet at 0x1fa4a1a3e20: work(3)> 0
<_DummyThread(Dummy-1, started daemon 2174496685600)>
<Greenlet at 0x1fa4a2b1120: work(3)> 0
<_DummyThread(Dummy-2, started daemon 2174497788192)>
<Greenlet at 0x1fa4a2c13a0: work(3)> 0
<_DummyThread(Dummy-3, started daemon 2174497854368)>
<Greenlet at 0x1fa4a1a3e20: work(3)> 1
<_DummyThread(Dummy-1, started daemon 2174496685600)>
<Greenlet at 0x1fa4a2b1120: work(3)> 1
<_DummyThread(Dummy-2, started daemon 2174497788192)>
<Greenlet at 0x1fa4a2c13a0: work(3)> 1
<_DummyThread(Dummy-3, started daemon 2174497854368)>
<Greenlet at 0x1fa4a1a3e20: work(3)> 2
<_DummyThread(Dummy-1, started daemon 2174496685600)>
<Greenlet at 0x1fa4a2b1120: work(3)> 2
<_DummyThread(Dummy-2, started daemon 2174497788192)>
<Greenlet at 0x1fa4a2c13a0: work(3)> 2
<_DummyThread(Dummy-3, started daemon 2174497854368)>
<_MainThread(MainThread, started 2174463857152)>

我们可以用threading.current_thread()来查看每个g1、g2和g3，查看的结果为DummyThread-n，即假线程

注意

当前程序是一个死循环并且还能有耗时操作，就不需要加上join方法了,因为程序需要一直运行不会退出。

代码示例：

import gevent
import time
from gevent import monkey

# 打补丁，让gevent框架识别耗时操作，比如：time.sleep，网络请求延时
monkey.patch_all()


# 任务1
def work1(num):
    for i in range(num):
        print("work1....")
        time.sleep(0.2)
        # gevent.sleep(0.2)

# 任务1
def work2(num):
    for i in range(num):
        print("work2....")
        time.sleep(0.2)
        # gevent.sleep(0.2)



if __name__ == '__main__':
    # 创建协程指定对应的任务
    g1 = gevent.spawn(work1, 3)
    g2 = gevent.spawn(work2, 3)

    while True:
        print("主线程中执行")
        time.sleep(0.5)

结果：

主线程中执行
work1....
work2....
work1....
work2....
work1....
work2....
主线程中执行
主线程中执行
主线程中执行
..省略..

Gevent之同步与异步

from gevent import spawn,joinall,monkey;monkey.patch_all()

import time
def task(pid):
    """
    Some non-deterministic task
    """
    time.sleep(0.5)
    print('Task %s done' % pid)


def synchronous():
    for i in range(10):
        task(i)

def asynchronous():
    g_l=[spawn(task,i) for i in range(10)]
    joinall(g_l)

if __name__ == '__main__':
    print('Synchronous:')
    synchronous()

    print('Asynchronous:')
    asynchronous()
#上面程序的重要部分是将task函数封装到Greenlet内部线程的gevent.spawn。 初始化的greenlet列表存放在数组threads中，此数组被传给gevent.joinall 函数，后者阻塞当前流程，并执行所有给定的greenlet。执行流程只会在 所有greenlet执行完后才会继续向下走。

Gevent之应用举例一

协程应用：爬虫

from gevent import monkey;monkey.patch_all()
import gevent
import requests
import time

def get_page(url):
    print('GET: %s' %url)
    response=requests.get(url)
    if response.status_code == 200:
        print('%d bytes received from %s' %(len(response.text),url))


start_time=time.time()
gevent.joinall([
    gevent.spawn(get_page,'https://www.python.org/'),
    gevent.spawn(get_page,'https://www.yahoo.com/'),
    gevent.spawn(get_page,'https://github.com/'),
])
stop_time=time.time()
print('run time is %s' %(stop_time-start_time))

Gevent之应用举例二

通过gevent实现单线程下的socket并发（from gevent import monkey;monkey.patch_all()一定要放到导入socket模块之前，否则gevent无法识别socket的阻塞。

服务端：

from gevent import monkey;monkey.patch_all()
from socket import *
import gevent

#如果不想用money.patch_all()打补丁,可以用gevent自带的socket
# from gevent import socket
# s=socket.socket()

def server(server_ip,port):
    s=socket(AF_INET,SOCK_STREAM)
    s.setsockopt(SOL_SOCKET,SO_REUSEADDR,1)
    s.bind((server_ip,port))
    s.listen(5)
    while True:
        conn,addr=s.accept()
        gevent.spawn(talk,conn,addr)

def talk(conn,addr):
    try:
        while True:
            res=conn.recv(1024)
            print('client %s:%s msg: %s' %(addr[0],addr[1],res))
            conn.send(res.upper())
    except Exception as e:
        print(e)
    finally:
        conn.close()

if __name__ == '__main__':
    server('127.0.0.1',8080)

客户端：

from socket import *

client=socket(AF_INET,SOCK_STREAM)
client.connect(('127.0.0.1',8080))


while True:
    msg=input('>>: ').strip()
    if not msg:continue

    client.send(msg.encode('utf-8'))
    msg=client.recv(1024)
    print(msg.decode('utf-8'))

多线程并发多个客户端:

from threading import Thread
from socket import *
import threading

def client(server_ip,port):
    c=socket(AF_INET,SOCK_STREAM) #套接字对象一定要加到函数内，即局部名称空间内，放在函数外则被所有线程共享，则大家公用一个套接字对象，那么客户端端口永远一样了
    c.connect((server_ip,port))

    count=0
    while True:
        c.send(('%s say hello %s' %(threading.current_thread().getName(),count)).encode('utf-8'))
        msg=c.recv(1024)
        print(msg.decode('utf-8'))
        count+=1
if __name__ == '__main__':
    for i in range(500):
        t=Thread(target=client,args=('127.0.0.1',8080))
        t.start()

标签：__,spawn,编程,并发,Gevent,gevent,time,print,import
From： https://www.cnblogs.com/xiao01/p/18049749

并发编程之Gevent模块