explicit joining of python threads?

Question

I need to start some threads in a python program. The threads perform a background task which might take a long time, so I don't want to block the main thread waiting on the task to happen.

Python provides the ability to 'reap' threads using Thread.join() and Thread.isAlive(). But I don't actually care about finding out when the thread has finished. I'm content to start up the thread, let it do it's thing and never worry about it again.

The question is, do I need to keep references around to the Thread objects that I start so that I can later join() them? Or can I just let the reference to the Thread object go out of scope and not worry about it? Is there a 'right' thing to do in this case?

Answer 1

You don't have to explicitly join threads -- just make sure they're not "daemonized" (leave their daemon attribute to the default, False) so they'll keep the process alive until they're all done (if you make your threads daemons, then you must make sure the main thread does not terminate until all relevant threads are done, or else the threads will be killed by the OS).

I think the right thing is the simplest one: forget about your "background threads", just make them non-daemons (which is after all their default state).