How to exit the entire application from a Python thread?

Question

How can I exit my entire Python application from one of its threads? sys.exit() only terminates the thread in which it is called, so that is no help.

I would not like to use an os.kill() solution, as this isn't very clean.

Answer 1

Short answer: use os._exit.

Long answer with example:

I yanked and slightly modified a simple threading example from a tutorial on DevShed:

import threading, sys, os

theVar = 1

class MyThread ( threading.Thread ):

   def run ( self ):

      global theVar
      print 'This is thread ' + str ( theVar ) + ' speaking.'
      print 'Hello and good bye.'
      theVar = theVar + 1
      if theVar == 4:
          #sys.exit(1)
          os._exit(1)
      print '(done)'

for x in xrange ( 7 ):
   MyThread().start()

If you keep sys.exit(1) commented out, the script will die after the third thread prints out. If you use sys.exit(1) and comment out os._exit(1), the third thread does not print (done), and the program runs through all seven threads.

os._exit "should normally only be used in the child process after a fork()" -- and a separate thread is close enough to that for your purpose. Also note that there are several enumerated values listed right after os._exit in that manual page, and you should prefer those as arguments to os._exit instead of simple numbers like I used in the example above.

Answer 2

If all your threads except the main ones are daemons, the best approach is generally thread.interrupt_main() -- any thread can use it to raise a KeyboardInterrupt in the main thread, which can normally lead to reasonably clean exit from the main thread (including finalizers in the main thread getting called, etc). Of course, if this results in some non-daemon thread keeping the whole process alive, you need to followup with os._exit as Mark recommends -- but I'd see that as the last resort (kind of like a kill -9;-) because it terminates things quite brusquely (finalizers not run, including try/finally blocks, with blocks, atexit functions, etc, etc).