协程下的爬虫

from urllib import request
import gevent, time
from gevent import monkey  //在没有加上此句和下一句时，运行速度理论上是一样的，因为gevent检测不到I/O端口
monkey.patch_all()

def f(url):
    print('GET:%s'%url)
    resp = request.urlopen(url)
    data = resp.read()
    print('%d bytes received from %s' % (len(data),url))
#用循环的方式爬虫，也就时串行
urls = ['https://www.python.org/','https://www.yahoo.com/']
start_time = time.time()
for url in urls:
    f(url)
print('The asynchronous total time is {time}'.format(time = time.time() - start_time))
#用协程方式爬虫
async_time = time.time()
gevent.joinall([gevent.spawn(f,'https://www.python.org/'),
                gevent.spawn(f,'https://www.yahoo.com/'),
                ])
print('The total time is {time}'.format(time = time.time() - async_time))

 运行的结果如下：

GET:https://www.python.org/
48835 bytes received from https://www.python.org/
GET:https://www.yahoo.com/
498399 bytes received from https://www.yahoo.com/
The total time is 12.665598630905151
GET:https://www.python.org/
GET:https://www.yahoo.com/
48835 bytes received from https://www.python.org/
498546 bytes received from https://www.yahoo.com/
The asynchronous total time is 5.80000114440918