Python threading: Is there a way to detect a join() call in a thread?

Question

I have created a program that runs X number of threads which all need to be able to be closed down by the main thread. Currently I can stop the program so that each thread will be abruptly killed. I want to be able to detect the close and handle it more gracefully. To do this I want to use the join() function, which waits for the threads to finish. The issue is that the threads don't have a set end and so calling join() would mean that the main thread will wait forever for the threads to end.

So the question is. Is there a way to detect a join() call in a thread and write a customized response to it?

Why do you want `join` to be the signal? Why not use a mechanism designed for sending messages between threads? — user2357112, Jan 29 '18 at 21:34
That would work just as well. I'm relatively new to python threading. Would you mind pushing me in the right direction regarding passing messages between threads? — Frederik Petersen, Jan 29 '18 at 21:36
For this particular use case, an [Event](https://docs.python.org/3/library/threading.html#threading.Event) seems appropriate. — user2357112, Jan 29 '18 at 21:38

score 1 · Accepted Answer · answered Jan 29 '18 at 21:37

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You can handle the stop signal outside your threads (with signal module, like this), set a flag on your threads asking them to stop processing and call join in your main thread.

answered Jan 29 '18 at 21:37

Thiago F. Pappacena

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Python threading: Is there a way to detect a join() call in a thread?

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