Cancellable threading.Timer in Python

Question

I am trying to write a method that counts down to a given time and unless a restart command is given, it will execute the task. But I don't think Python threading.Timer class allows for timer to be cancelable.

import threading  def countdown(action):     def printText():         print 'hello!'      t = threading.Timer(5.0, printText)     if (action == 'reset'):         t.cancel()      t.start() 

I know the above code is wrong somehow. Would appreciate some kind guidance over here.

Answer 1

You would call the cancel method after you start the timer:

import time import threading  def hello():     print "hello, world"     time.sleep(2)  t = threading.Timer(3.0, hello) t.start() var = 'something' if var == 'something':     t.cancel() 

You might consider using a while-loop on a Thread, instead of using a Timer.
Here is an example appropriated from Nikolaus Gradwohl's answer to another question:

import threading import time  class TimerClass(threading.Thread):     def __init__(self):         threading.Thread.__init__(self)         self.event = threading.Event()         self.count = 10      def run(self):         while self.count > 0 and not self.event.is_set():             print self.count             self.count -= 1             self.event.wait(1)      def stop(self):         self.event.set()  tmr = TimerClass() tmr.start()  time.sleep(3)  tmr.stop()