from datetime import datetime, timedelta
now_time = datetime.now() # datetime.datetime(2015, 10, 22, 16, 56, 51, 924895)
str_now = str(now_time).split(‘.‘)[0]
date_last_time = datetime.strptime(last_pull_time,‘%Y-%m-%d %H:%M:%S‘)
原文：http://my.oschina.net/u/2367514/blog/520903