class SLTimer(multiprocessing.Process):     #from datetime import datetime     #import time     def __init__(self, target=None, args=(), kwargs={},date=None,time=None):         '''\         @param date 1900-01-01         @param time 00:00:00         '''         super(SLTimer,self).__init__(target=target,args=args,kwargs=kwargs)         _date = ''         if date is None:             _date = datetime.now().__str__()[:10]         else :             _date = date         _time = ''         if time is None:             _time = datetime.now().__str__()[11:19]         else:             _time = time         self.__runtime = '%s %s' % (_date,_time)     def run(self):         timeLen = len('1900-00-00 00:00:00')         while True:             now = datetime.now().__str__()[:timeLen]             if now>=self.__runtime:                 break             print 'sleeping... %s' % now             time.sleep(1.0)         super(SLTimer,self).run()

def show1():     from datetime import datetime     print 'hello,current time:%s' % datetime.now().__str__() def t23():     from  stock.task import SLTimer     timer = SLTimer(show1, time='16:31:50')     timer.start()