用到的库：datetime.datetime.now() datetime.datetime.strptime() datetime.timedelta()
数据模拟：
>>> from datetime import datetime, timedelta
>>> nowtime = datetime.now() # 现在的时间
>>> nowtime
datetime.datetime(2017, 6, 20, 20, 11, 12, 926763)
>>>
>>> lasthour = datetime(2017, 6, 20, 19, 11, 12, 926763) # 1个小时前的时间
>>> lasthour
datetime.datetime(2017, 6, 20, 19, 11, 12, 926763)
>>> lasthour_str = str(lasthour) # 模拟从数据库取出来的str类型时间数据
>>> lasthour_str
'2017-06-20 19:11:12.926763'
str时间数据转换：
# 将str类型时间数据转换为datetime.datetime类型时间数据
>>> lasthour_new = datetime.strptime(lasthour_str, '%Y-%m-%d %H:%M:%S.%f')
>>> lasthour_new
datetime.datetime(2017, 6, 20, 19, 11, 12, 926763)
时间比较：
# lasthour_new和nowtime的时间差是否大于1个小时
>>> nowtime - lasthour_new > timedelta(hours=1)
False
# lasthour_new和nowtime的时间差是否等于1个小时
>>> nowtime - lasthour_new == timedelta(hours=1)
True
# lasthour_new和nowtime的时间差是否大于60分钟
>>> nowtime - lasthour_new > timedelta(minutes=60)
False
# lasthour_new和nowtime的时间差是否等于60分钟
>>> nowtime - lasthour_new == timedelta(minutes=60)
True