Run certain code every n seconds [duplicate]

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Run certain code every n seconds [duplicate]

Is there a way to, for example, print Hello World! every n seconds?
For example, the program would go through whatever code I had, then once it had been 5 seconds (with time.sleep()) it would execute that code. I would be using this to update a file though, not print Hello World.

For example:

startrepeat("print('Hello World')", .01) # Repeats print('Hello World') ever .01 seconds
for i in range(5):
    print(i)
>> Hello World!
>> 0
>> 1
>> 2
>> Hello World!
>> 3
>> Hello World!
>> 4

Answer #1:

import threading
def printit():
  threading.Timer(5.0, printit).start()
  print "Hello, World!"
printit()
# continue with the rest of your code

https://docs.python.org/3/library/threading.html#timer-objects

Answered By: Alex Martelli

Answer #2:

My humble take on the subject, a generalization of Alex Martelli’s answer, 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!
Answered By: MestreLion

Answer #3:

def update():
    import time
    while True:
        print 'Hello World!'
        time.sleep(5)

That’ll run as a function. The while True: makes it run forever. You can always take it out of the function if you need.

Answered By: avacariu

Answer #4:

Save yourself a schizophrenic episode and use the Advanced Python scheduler:
http://pythonhosted.org/APScheduler

The code is so simple:

from apscheduler.scheduler import Scheduler
sched = Scheduler()
sched.start()
def some_job():
    print "Every 10 seconds"
sched.add_interval_job(some_job, seconds = 10)
....
sched.shutdown()
Answered By: Yan King Yin

Answer #5:

Here is a simple example compatible with APScheduler 3.00+:

# note that there are many other schedulers available
from apscheduler.schedulers.background import BackgroundScheduler
sched = BackgroundScheduler()
def some_job():
    print('Every 10 seconds')
# seconds can be replaced with minutes, hours, or days
sched.add_job(some_job, 'interval', seconds=10)
sched.start()
...
sched.shutdown()

Alternatively, you can use the following. Unlike many of the alternatives, this timer will execute the desired code every n seconds exactly (irrespective of the time it takes for the code to execute). So this is a great option if you cannot afford any drift.

import time
from threading import Event, Thread
class RepeatedTimer:
    """Repeat `function` every `interval` seconds."""
    def __init__(self, interval, function, *args, **kwargs):
        self.interval = interval
        self.function = function
        self.args = args
        self.kwargs = kwargs
        self.start = time.time()
        self.event = Event()
        self.thread = Thread(target=self._target)
        self.thread.start()
    def _target(self):
        while not self.event.wait(self._time):
            self.function(*self.args, **self.kwargs)
    @property
    def _time(self):
        return self.interval - ((time.time() - self.start) % self.interval)
    def stop(self):
        self.event.set()
        self.thread.join()
# start timer
timer = RepeatedTimer(10, print, 'Hello world')
# stop timer
timer.stop()
Answered By: Six

Answer #6:

Here’s a version that doesn’t create a new thread every n seconds:

from threading import Event, Thread
def call_repeatedly(interval, func, *args):
    stopped = Event()
    def loop():
        while not stopped.wait(interval): # the first call is in `interval` secs
            func(*args)
    Thread(target=loop).start()
    return stopped.set

The event is used to stop the repetitions:

cancel_future_calls = call_repeatedly(5, print, "Hello, World")
# do something else here...
cancel_future_calls() # stop future calls

See Improve current implementation of a setInterval python

Answered By: jfs

Answer #7:

You can start a separate thread whose sole duty is to count for 5 seconds, update the file, repeat. You wouldn’t want this separate thread to interfere with your main thread.

Answered By: Kit
The answers/resolutions are collected from stackoverflow, are licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0 .

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