# 日期(两种方法)
# 1
str = time.strftime("%Y%m%d", time.localtime(time.time()))
# 2
today = datetime.date.today()
str = datetime.datetime.strftime(today , '%Y%m%d')
# 其中第二个datetime可以进行天数加减操作,例如(三天前):
threedaysbrfore = datetime.date.today() + datetime.timedelta(-3)