Run a function at the start of every round 5 minute interval

Question

I want to run a function every 5 minutes, it must be at a "round" intervals, for example :

12:05:00, 12:10:00, 12:15:00...

It cannot be like this:

12:06:00, 12:11:00, 12:16:00...

Or like this:

12:05:14, 12:10:14, 12:15:14...

What is the most accurate way to do this in python?

Answer 1

You could use a threading.Timer. You have to do some math to calculate the next run time. datetime has a handy replace method for that.

from datetime import datetime, timedelta
from threading import Timer
from time import sleep
import random

def schedule_next_run():
    sleep_time = get_sleep_time()
    t = Timer(sleep_time, do_work)
    t.daemon = True
    t.start()
    print(f'sleeping for {sleep_time} seconds')

def get_sleep_time():
    now = datetime.now()
    last_run_time = now.replace(minute=now.minute // 5 * 5, second=0, microsecond=0)
    next_run_time = last_run_time + timedelta(minutes=5)
    return (next_run_time - now).total_seconds()

def do_work():
    now = datetime.now()
    print('Doing some work at', now)
    sleep(random.uniform(0, 29))
    print('Work complete. Scheduling next run.')
    schedule_next_run()

print('Starting work schedule')
schedule_next_run()
input('Doing work every 5 minutes. Press enter to exit:\n')

On my system, the function fires within a half millisecond of the target time

Note that the time calculation rounds down and then adds a timedelta to carefully wrap around the end of each hour. You would want to ponder how this will behave around daylight savings changes.

Suggestion: move all this logic to a class to clean it up.