Countdown using twisted LoopingCall class

countdown.py

from twisted.internet import reactor
from twisted.internet.task import LoopingCall


class Countdown(object):

    def __init__(self, counter, freq):
        self.counter = counter
        self.freq = freq
        self.lc = LoopingCall(self.count)
        self.lc.start(self.freq)

    def count(self):
        if self.counter == 0:
            self.lc.stop()
            reactor.stop()
        else:
            print "%s: %s" % (self.freq, self.counter)
            self.counter -= 1


print 'Start!'

Countdown(5, 1)
Countdown(6, 2)
Countdown(7, 3)

reactor.run()

print 'Stop!'