首先Python提供的协程库gevent好像并不能知道那些程序使用了io  所以要加一个补丁，mondey，以下同步和异步各爬一次的案例 ：

,

from urllib import request

import gevent,time

from gevent import monkey

monkey.patch_all() #把当前程序的所有的io操作给我单独的做上标记

def f(url):

print('GET: %s' % url)

resp = request.urlopen(url)

data = resp.read()

print('%d bytes received from %s.' % (len(data), url))

urls = ['https://www.python.org/',

'https://www.yahoo.com/',

'https://github.com/' ]

time_start = time.time()

for url in urls:

f(url)

print("同步cost",time.time() - time_start)

async_time_start = time.time()

gevent.joinall([

gevent.spawn(f, 'https://www.python.org/'),

gevent.spawn(f, 'https://www.yahoo.com/'),

gevent.spawn(f, 'https://github.com/'),

])

print("异步cost",time.time() - async_time_start)