How to execute a function asynchronously every 60 seconds in Python?

Question

Hello,

I want to execute a function every 60 seconds on Python but I don't want to be blocked meanwhile.

How can I do it asynchronously?

import threading
import time

def f():
    print("hello world")
    threading.Timer(3, f).start()

if __name__ == '__main__':
    f()    
    time.sleep(20)

With this code, the function f is executed every 3 seconds within the 20 seconds time.time. At the end it gives an error and I think that it is because the threading.timer has not been canceled.

How can I cancel it?

Thanks in advance!

Answer 1

Why dont you create a dedicated thread, in which you put a

while true:
   stuff_todo
   sleep 60

Answer 2

You could try the threading.Timer class: http://docs.python.org/library/threading.html#timer-objects.

def f():
    # do something here ...
    # call f() again in 60 seconds
    threading.Timer(60, f).start()

# start calling f now and every 60 sec thereafter
f()

Answer 3

The simplest way is to create a background thread that runs something every 60 seconds. A trivial implementation is:

class BackgroundTimer(Thread):   
   def run(self):
      while 1:
        Time.sleep(60)
        # do something


# ... SNIP ...
# Inside your main thread
# ... SNIP ...

timer = BackgroundTimer()
timer.start()

Obviously, this if the "do something" takes a long time, you'll need to accommodate for it in your sleep statement. But this serves as a good approximation.

Answer 4

It depends on what you actually want to do in the mean time. Threads are the most general and least preferred way of doing it; you should be aware of the issues with threading when you use it: not all (non-Python) code allows access from multiple threads simultaneously, communication between threads should be done using thread-safe datastructures like Queue.Queue, you won't be able to interrupt the thread from outside it, and terminating the program while the thread is still running can lead to a hung interpreter or spurious tracebacks.

Often there's an easier way. If you're doing this in a GUI program, use the GUI library's timer or event functionality. All GUIs have this. Likewise, if you're using another event system, like Twisted or another server-process model, you should be able to hook into the main event loop to cause it to call your function regularly. The non-threading approaches do cause your program to be blocked while the function is pending, but not between functioncalls.