Run certain code every n seconds

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

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!

Save yourself a schizophrenic episode and use the Advanced Python scheduler:

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()

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.