Python thread exit code

Question

Is there a way to tell if a thread has exited normally or because of an exception?

score 20 · Accepted Answer · edited Nov 22 '18 at 15:11

As mentioned, a wrapper around the Thread class could catch that state. Here's an example.

>>> from threading import Thread
>>> class MyThread(Thread):
    def run(self):
        try:
            Thread.run(self)
        except Exception as err:
            self.err = err
            pass # or raise err
        else:
            self.err = None


>>> mt = MyThread(target=divmod, args=(3, 2))
>>> mt.start()
>>> mt.join()
>>> mt.err
>>> mt = MyThread(target=divmod, args=(3, 0))
>>> mt.start()
>>> mt.join()
>>> mt.err
ZeroDivisionError('integer division or modulo by zero',)

score 0 · Answer 2 · answered Jun 12 '09 at 13:33

0

You could set some global variable to 0 if success, or non-zero if there was an exception. This is a pretty standard convention.

However, you'll need to protect this variable with a mutex or semaphore. Or you could make sure that only one thread will ever write to it and all others would just read it.

answered Jun 12 '09 at 13:33

samoz

56,849
55
141
195

1

0 for success may be a pretty standard convention, but wouldn't a boolean `succeded` be a little easier on the meat interpreter? – Daren Thomas Jun 12 '09 at 13:38
It doesn't have to be global if I subclass Thread, just need a member variable in that to indicate success. I was just wondering if there is any builtin way to do this, like the process exit code. – Jiayao Yu Jun 12 '09 at 13:48
9

Threads and global state. Two great tastes tthat tate gsrat eogetherrrrrrrrrrrrrrr Segmentation fault, core dumped. – Glyph Jun 15 '09 at 14:55
@Glyph note how I mentioned mutexs and semaphores though. – samoz Jun 15 '09 at 15:20

score 0 · Answer 3 · answered Jun 12 '09 at 13:43

Have your thread function catch exceptions. (You can do this with a simple wrapper function that just calls the old thread function inside a try...except or try...except...else block). Then the question just becomes "how to pass information from one thread to another", and I guess you already know how to do that.

Python thread exit code

3 Answers3

Linked