1. 计算给出两个时间之间的时间差
import datetime as dt
# current time
cur_time = dt.datetime.today()
# one day
pre_time = dt.date(2016, 5, 20) # eg: 2016.5.20
delta = cur_time - pre_time
# if you want to get discrepancy in days
print delta.days
# if you want to get discrepancy in hours
print delta.hours
# and so
