1、计算时间差：
import datetime
starttime = datetime.datetime.now()
endtime = datetime.datetime.now()
print (endtime - starttime).seconds
2、执行shell命令：
import subprocess
ret = subprocess.Popen(CMD,shell=True,stdout=subprocess.PIPE,stderr=subprocess.STDOUT)
for line in ret.stdout.readlines():
print line
3、简单的urllib2使用：
import urllib2
res=urllib2.urlopen(url)
print res.read()