python 定义一个类，类里有一个实例属性是关于时间的，怎么样写才能让这个属性根据时间变化？

关于这个问题，我写了个简单的实例。下边的实例每次都是打印的时间是一样的，怎么才能打印当时的时间

import time
import schedule

class ShortMessage:
def init(self, message_time=None):
self.message_time = message_time

if self.message_time == '7':
self.time_sj = time.strftime(
'%Y%m%d %H:%M:%S 7', time.localtime())
elif self.message_time == '17':
self.time_sj = time.strftime(
'%Y%m%d %H:%M:%S 17', time.localtime())

def pr(self):
print(self.__time_sj)

task_07 = ShortMessage(message_time='7')
task_17 = ShortMessage(message_time='17')
schedule.every().day.at(
'08:15').do(task_07.pr)
schedule.every().day.at(
'08:20').do(task_17.pr)
schedule.every().day.at(
'08:25').do(task_07.pr)
schedule.every().day.at(
'08:30').do(task_17.pr)

while True:
schedule.run_pending()
time.sleep(60)