Thread Basics

Take a look at the threading module.

An example :

from threading import Thread

# instanciate a new thread
t = Thread(target=my_task)
# let it do the time-consuming stuff
t.start()
# do extra stuff while t is working
do_extra_stuff()
# wait for t to finish
t.join()

Getting Task Result

However, if you want to get a value from my_task, you'll need to either use global variable, mutable parameter or wrap your task into a class extanding Thread.

Here's an example with a wrapping class :

class MyThread(Thread):

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.result = None

    def run(self):  # this is the Thread method you need to override
        # the time consuming stuff
        self.result = some_result

# same as before, but using the new class, so no need to specify target.
t = MyThread()
t.start() # will call t.run() for you. Never call t.run yourself (you'll lose every benefit from using Thread)
t.join() # wait for t to be finished before getting result
print(t.result)

Passing Arguments

To pass arguments to the task (including the callback), you can either put them as class fields and fill them in the construcor, or use the args kwarg from Thread's construcor, like this :

t = Thread(target=task_with_parametters, args=(arg1, arg2))

Thread will call task_with_parametters like this :

task_with_parametters(arg1, arg2)