python – What is the best way to repeatedly execute a function every x seconds?

python – What is the best way to repeatedly execute a function every x seconds?

If your program doesnt have a event loop already, use the sched module, which implements a general purpose event scheduler.

import sched, time
s = sched.scheduler(time.time, time.sleep)
def do_something(sc): 
    print(Doing stuff...)
    # do your stuff
    s.enter(60, 1, do_something, (sc,))

s.enter(60, 1, do_something, (s,))
s.run()

If youre already using an event loop library like asyncio, trio, tkinter, PyQt5, gobject, kivy, and many others – just schedule the task using your existing event loop librarys methods, instead.

Lock your time loop to the system clock like this:

import time
starttime = time.time()
while True:
    print(tick)
    time.sleep(60.0 - ((time.time() - starttime) % 60.0))

python – What is the best way to repeatedly execute a function every x seconds?

If you want a non-blocking way to execute your function periodically, instead of a blocking infinite loop Id use a threaded timer. This way your code can keep running and perform other tasks and still have your function called every n seconds. I use this technique a lot for printing progress info on long, CPU/Disk/Network intensive tasks.

Heres the code Ive posted in a similar question, with start() and stop() control:

from threading import Timer

class RepeatedTimer(object):
    def __init__(self, interval, function, *args, **kwargs):
        self._timer     = None
        self.interval   = interval
        self.function   = function
        self.args       = args
        self.kwargs     = kwargs
        self.is_running = False
        self.start()

    def _run(self):
        self.is_running = False
        self.start()
        self.function(*self.args, **self.kwargs)

    def start(self):
        if not self.is_running:
            self._timer = Timer(self.interval, self._run)
            self._timer.start()
            self.is_running = True

    def stop(self):
        self._timer.cancel()
        self.is_running = False

Usage:

from time import sleep

def hello(name):
    print Hello %s! % name

print starting...
rt = RepeatedTimer(1, hello, World) # it auto-starts, no need of rt.start()
try:
    sleep(5) # your long-running job goes here...
finally:
    rt.stop() # better in a try/finally block to make sure the program ends!

Features:

  • Standard library only, no external dependencies
  • start() and stop() are safe to call multiple times even if the timer has already started/stopped
  • function to be called can have positional and named arguments
  • You can change interval anytime, it will be effective after next run. Same for args, kwargs and even function!

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