python 定时任务

import time,datetime
res = datetime.datetime(2018,1,11,11,0,0)     #设置一个时间，从某个时刻开始。本例子是从今天11点开始，每隔5秒钟执行以下打印命令
while True:
    now = datetime.datetime.now()
    # res = datetime.datetime(2018,1,11,9,55,0)
    # print(datetime.datetime(2018,1,11,9,50,10))
    if   res < now < (res + datetime.timedelta(seconds=5)):
        res = res + datetime.timedelta(seconds=5)
        a = str(now)
        b = a[17]+a[18]
        print('time.time.time%s'%b)
        # func()
        time.sleep(5)