Running a background thread in python

Question

All the examples I've been able to get to don't really address my problem, of having a certain procedure in the background constantly looping, while the rest of the program continues.

Here is a simple example of a method that works, using _thread:

import _thread
import time


def countSeconds():
    time.sleep(1)
    print("Second")
    _thread.start_new(countSeconds, ())

def countTenSeconds():
    time.sleep(10)
    print("Ten seconds passed")
    _thread.start_new(countTenSeconds, ())


_thread.start_new(countSeconds, ())
_thread.start_new(countTenSeconds, ())

Ignoring the obvious fact that we could track the seconds, and just print something different if it's a multiple of ten, how would I go about creating this more efficiently.

In my actual program, the threading seems to be guzzling RAM, I assume from creating multiple instance of the thread. Do I have to "start_new" thread at the end of each procedure?

Thanks for any help.

Re-calling a thread in itself doesn't seem really reasonable, maybe something like this is what you need: stackoverflow.com/questions/12435211/… — Philip Feldmann
– Philip Feldmann, Commented Jan 12, 2016 at 16:59
Is there any reason you're not using the threading module? It will be simpler than using the low-level _thread module. Also, thanks to the GIL, threaded Python applications are not actually parallel - you need multiprocessing for that. — skrrgwasme
– skrrgwasme, Commented Jan 12, 2016 at 17:03
i agree with @skrrgwasme. I would be using threading (or asyncio). Furthermore, this is the whole objective of threading (run multiple threads [tasks] concurrently within a single process)... — darren
– darren, Commented Nov 22, 2023 at 14:55

tglaria · Accepted Answer · 2023-11-23 16:46:22Z

8

All the examples I've been able to get to don't really address my problem Which examples?

This does work for me.

import threading
import time

def f():
    time.sleep(1)
    print "Function out!"

t1 = threading.Thread(target=f)

print "Starting thread"
t1.start()
time.sleep(0.1)
print "Something done"
t1.join()
print "Thread Done"

You're asking for a repeated thread, I don't get what exactly you need, this might work:

import threading
import time

var = False
def f():
    counter = 0
    while var:
        time.sleep(0.1)
        print "Function {} run!".format(counter)
        counter+=1

t1 = threading.Thread(target=f)

print "Starting thread"
var = True
t1.start()
time.sleep(3)
print "Something done"
var = False
t1.join()
print "Thread Done"

edited Nov 23, 2023 at 16:46

answered Jan 12, 2016 at 18:31

tglaria

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1 Comment

Constantly Confused Over a year ago

The problem with this example is that it is not recursive. It is running the function once, and then quitting.

Freakin · Accepted Answer · 2017-10-23 21:34:25Z

4

use the threading.timer to continue launching a new background thread

import threading
import time


def countSeconds():
    print("Second")
    threading.Timer(1, countSeconds).start()

def countTenSeconds():
    print("Ten seconds passed")
    threading.Timer(10, countTenSeconds).start()


threading.Timer(1, countSeconds).start()
threading.Timer(10, countTenSeconds).start()

answered Oct 23, 2017 at 21:34

Freakin

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