How to run a method in the background using Python

Question

I'm trying to run a method in the background of python (a class that is constantly updated by messages from an aws server) and I'm using this as a template. Problem is, I can't get it to print('checkpoint') or print('bye'). It just keeps running the run(self). Why is that?

import threading
import time


class ThreadingExample(object):
    """ Threading example class
    The run() method will be started and it will run in the background
    until the application exits.
    """

    def __init__(self, interval=1):
        """ Constructor
        :type interval: int
        :param interval: Check interval, in seconds
        """
        self.interval = interval

        thread = threading.Thread(target=self.run, args=())
        thread.daemon = True                            # Daemonize thread
        thread.start()                                  # Start the execution

    def run(self):
        """ Method that runs forever """
        while True:
            # Do something
            print('Doing something imporant in the background')

            time.sleep(self.interval)

example = ThreadingExample()
time.sleep(3)
print('Checkpoint')
time.sleep(2)
print('Bye')

EDIT: I forgot to mention I'm using Python 2.7.6 on Ubuntu 14.04 LTS 64-bit

could you show your output and your expected output. It seems to work in my python 2.7 environment output Doing something imporant in the background Doing something imporant in the background Doing something imporant in the background Checkpoint Doing something imporant in the background Doing something imporant in the background Bye — The6thSense
– The6thSense, Commented Jan 5, 2016 at 5:57
My expected output is exactly what you put but instead it just keeps repeating 'Doing something important in the background' until I interupt it — Rishi
– Rishi, Commented Jan 5, 2016 at 6:01
did you try running it through cmd line and not your interpreter like canopy , pycharm etc.. — The6thSense
– The6thSense, Commented Jan 5, 2016 at 6:05
You should ensure the thread started before starting your loop — smac89
– smac89, Commented Jan 5, 2016 at 6:08
Why don't you use Python 3? Your use of print with a function syntax suggests it is Python 3 already, so you wouldn' even have to change anything. — Ulrich Eckhardt
– Ulrich Eckhardt, Commented Jan 5, 2016 at 6:11

The6thSense · Accepted Answer · 2016-01-05 06:05:02Z

1

I've run your code it works fine (python34, ubuntu14)

with thread.daemon = True:

Doing something important in the background
Doing something important in the background
Doing something important in the background
Checkpoint
Doing something important in the background
Doing something important in the background
Bye

with daemon = False:

Doing something imporant in the background
Doing something important in the background
Doing something important in the background
Checkpoint
Doing something important in the background
Doing something important in the background
Bye
Doing something important in the background
Doing something important in the background
Doing something important in the background
Doing something important in the background
...

edited Jan 5, 2016 at 6:05

The6thSense

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answered Jan 5, 2016 at 6:02

Yoav Glazner

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Comments

Rishi · Accepted Answer · 2016-01-05 06:20:43Z

0

NEVER MIND I FIXED IT

Instead of

 thread = threading.Thread(target=self.run, args=())

I had

 thread = threading.Thread(target=self.run(), args=())

I don't know why but those brackets made it run forever

answered Jan 5, 2016 at 6:20

Rishi

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1 Comment

Yoav Glazner Over a year ago

when you write self.run() the function run is called from the current thread (and loops forever), -therefor you get stuck the in that call. no other thread will be created...

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