# Scheduling tasks for the future

Let's say we want to run a task X seconds in the future. The way to do that is defined in the reactor interface `twisted.internet.interfaces.IReactorTime`:

    from twisted.internet import reactor

    def f(s):
        print "this will run in 3.5 seconds: %s" % s

    reactor.callLater(3.5, f, "hello, world")

If we want a task to run every X seconds repeatedly, we can just re-add it every time it's run:

    from twisted.internet import reactor

    def runEverySecond():
        print "a second has passed"
        reactor.callLater(1, runEverySecond)

    reactor.callLater(1, runEverySecond)

If we want to cancel a task that we've scheduled:

    from twisted.internet import reactor

    def f():
        print "I'll never run."

    callID = reactor.callLater(5, f)
    callID.cancel()