Schedule a repeating event in Python 3

Question

I'm trying to schedule a repeating event to run every minute in Python 3.

I've seen class sched.scheduler but I'm wondering if there's another way to do it. I've heard mentions I could use multiple threads for this, which I wouldn't mind doing.

I'm basically requesting some JSON and then parsing it; its value changes over time.

To use sched.scheduler I have to create a loop to request it to schedule the even to run for one hour:

scheduler = sched.scheduler(time.time, time.sleep)

# Schedule the event. THIS IS UGLY!
for i in range(60):
    scheduler.enter(3600 * i, 1, query_rate_limit, ())

scheduler.run()

What other ways to do this are there?

Answer 1

You could use threading.Timer, but that also schedules a one-off event, similarly to the .enter method of scheduler objects.

The normal pattern (in any language) to transform a one-off scheduler into a periodic scheduler is to have each event re-schedule itself at the specified interval. For example, with sched, I would not use a loop like you're doing, but rather something like:

def periodic(scheduler, interval, action, actionargs=()):
    scheduler.enter(interval, 1, periodic,
                    (scheduler, interval, action, actionargs))
    action(*actionargs)

and initiate the whole "forever periodic schedule" with a call

periodic(scheduler, 3600, query_rate_limit)

Or, I could use threading.Timer instead of scheduler.enter, but the pattern's quite similar.

If you need a more refined variation (e.g., stop the periodic rescheduling at a given time or upon certain conditions), that's not too hard to accomodate with a few extra parameters.