Python class instance starts method in new thread

Question

I spent the last hour(s???) looking/googling for a way to have a class start one of its methods in a new thread as soon as it is instanciated.

I could run something like this:

x = myClass()

def updater():
    while True:
        x.update()
        sleep(0.01)

update_thread = Thread(target=updater) 
update_thread.daemon = True
update_thread.start()

A more elegant way would be to have the class doing it in init when it is instanciated. Imagine having 10 instances of that class... Until now I couldn't find a (working) solution for this problem... The actual class is a timer and the method is an update method that updates all the counter's variables. As this class also has to run functions at a given time it is important that the time updates won't be blocked by the main thread.

Any help is much appreciated. Thx in advance...

Answer 1

You can subclass directly from Thread in this specific case

from threading import Thread

class MyClass(Thread):
    def __init__(self, other, arguments, here):
        super(MyClass, self).__init__()
        self.daemon = True
        self.cancelled = False
        # do other initialization here

    def run(self):
        """Overloaded Thread.run, runs the update 
        method once per every 10 milliseconds."""

        while not self.cancelled:
            self.update()
            sleep(0.01)

    def cancel(self):
        """End this timer thread"""
        self.cancelled = True

    def update(self):
        """Update the counters"""
        pass

my_class_instance = MyClass()

# explicit start is better than implicit start in constructor
my_class_instance.start()

# you can kill the thread with
my_class_instance.cancel()

Answer 2

In order to run a function (or memberfunction) in a thread, use this:

th = Thread(target=some_func)
th.daemon = True
th.start()

Comparing this with deriving from Thread , it has the advantage that you don't export all of Thread's public functions as own public functions. Actually, you don't even need to write a class to use this code, self.function or global_function are both equally usable as target here.

I'd also consider using a context manager to start/stop the thread, otherwise the thread might stay alive longer than necessary, leading to resource leaks and errors on shutdown. Since you're putting this into a class, start the thread in __enter__ and join with it in __exit__ .