python并行化

#encoding=utf-8

from multiprocessing.dummy import Pool as ThreadPool
#导入pool类，命名为ThreadPool
import requests
import time

def getsource(url):
    html = requests.get(url)

urls = []
for i in range(1,21):
    newpage = 'http://tieba.baidu.com/p/3522395718?pn='+str(i)
    urls.append(newpage)

time1 = time.time()
# Python time time() 返回当前时间的时间戳（1970纪元后经过的浮点秒数）
for i in urls:
    print i
    getsource(i)
time2 = time.time()
print u'单线程耗时：'+str(time2-time1)

pool = ThreadPool(8)
time3 = time.time()
results = pool.map(getsource,urls)
pool.close()
pool.join()
time4 = time.time()
print u'并行耗时：'+str(time4-time3)