Python gevent模块

gevent是第三方库，通过greenlet实现协程，其基本思想是：

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，经常使程序处于等待状态，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。

由于切换是在IO操作时自动完成，所以gevent需要修改Python自带的一些标准库，这一过程在启动时通过monkey patch完成：

# -*- coding: utf-8 -*-'''Created on 2016/6/30@author: wwhhff11'''from gevent import monkeyimport geventmonkey.patch_socket()""" 线程数只有1个"""def f(n):    for i in range(n):        print gevent.getcurrent(), i        gevent.sleep(0)g1 = gevent.spawn(f, 5)g2 = gevent.spawn(f, 5)g3 = gevent.spawn(f, 5)g1.join()g2.join()g3.join()

# -*- coding: utf-8 -*-'''Created on 2016/6/30@author: wwhhff11'''from gevent import monkeyimport geventimport urllib2from time import timefrom gevent.pool import Poolfrom gevent.threadpool import ThreadPoolmonkey.patch_all()def f(url):    print 'GET: %s' % url    respone = urllib2.urlopen(url)    data = respone.read()    print '%d bytes received from %s.' % (len(data), url)start=time()# 7.55209708214gevent.joinall([gevent.spawn(f,"http://www.qq.com") for i in xrange(100)])# 35.4669699669# for i in xrange(100):#     f("http://www.qq.com")end=time()print end-start

# -*- coding: utf-8 -*-'''Created on 2016/6/30@author: wwhhff11'''from gevent import monkeyimport geventimport urllib2from time import timefrom gevent.pool import Poolfrom gevent.threadpool import ThreadPoolfrom gevent.queue import JoinableQueue, Emptyqueue = JoinableQueue()STOP="stop"monkey.patch_all()def html_reader():    while True:        try:            url=queue.get(0)            print 'GET: %s' % url            respone = urllib2.urlopen(url)            data = respone.read()            print '%d bytes received from %s.' % (len(data), url)        except Empty:            breakstart=time()readers = [gevent.spawn(html_reader) for i in xrange(10)]for i in range(100):    queue.put("http://www.qq.com")gevent.joinall(readers)end=time()print end-start

# -*- coding: utf-8 -*-'''Created on 2016/6/30@author: wwhhff11'''from gevent import monkeyimport geventimport urllib2from time import timefrom gevent.pool import Poolfrom gevent.threadpool import ThreadPoolfrom gevent.queue import JoinableQueue, Emptyqueue = JoinableQueue()STOP="stop"monkey.patch_all()def html_reader():    while True:        try:            url=queue.get(0)            print 'GET: %s' % url            respone = urllib2.urlopen(url)            data = respone.read()            print '%d bytes received from %s.' % (len(data), url)        except Empty:            breakstart=time()pool=ThreadPool(10)for i in range(100):    queue.put("http://www.qq.com")for i in xrange(10):    pool.spawn(html_reader)pool.join()end=time()print end-start

html_reader个数为1->33s
html_reader个数为10->6s

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