用Python编写简单的定时器的方法

下面介绍以threading模块来实现定时器的方法。

首先介绍一个最简单实现：

    import threading

    def say_sth(str):
      print str
      t = threading.Timer(2.0, say_sth,[str])
      t.start()

    if __name__ == '__main__':
      timer = threading.Timer(2.0,say_sth,['i am here too.'])
      timer.start()

不清楚在某些特殊应用场景下有什么缺陷否。

下面是所要介绍的定时器类的实现：

    class Timer(threading.Thread): 
          """ 
          very simple but useless timer. 
          """ 
          def __init__(self, seconds): 
              self.runTime = seconds 
              threading.Thread.__init__(self) 
          def run(self): 
              time.sleep(self.runTime) 
              print "Buzzzz!! Time's up!" 

      class CountDownTimer(Timer): 
          """ 
          a timer that can counts down the seconds. 
          """ 
          def run(self): 
              counter = self.runTime 
              for sec in range(self.runTime): 
                  print counter 
                  time.sleep(1.0) 
                  counter -= 1 
              print "Done" 

      class CountDownExec(CountDownTimer): 
          """ 
          a timer that execute an action at the end of the timer run. 
          """ 
          def __init__(self, seconds, action, args=[]): 
              self.args = args 
              self.action = action 
              CountDownTimer.__init__(self, seconds) 
          def run(self): 
              CountDownTimer.run(self) 
              self.action(self.args) 

      def myAction(args=[]): 
          print "Performing my action with args:" 
          print args 
      if __name__ == "__main__": 
          t = CountDownExec(3, myAction, ["hello", "world"]) 
          t.start()