CODEWITHSUNDEEP
pythonmultithreading
linkmaster03
linkmaster03

Reputation: 4358

How to exit the entire application from a Python thread?

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.

Upvotes: 109

Views: 134648

Answers (6)

user3901917
user3901917

Reputation: 167

Use threading.Event()

It allows you to handle errors and works on Windows and Linux.

Use this script to end all threads whenever you reach your desired threshold. In this case, I use it as a timeout.

Other solutions rely on potentially problematic os._exit, which this intentionally does not so that you can handle exceptions with try/except/finally blocks instead of just exiting. It also works for Python 2 and 3, which many answers do not.

This script will wait until either of your functions completes before finishing.

import time, queue, threading

def my_func(s):  # Function that you want to set a time limit for.
    # Insert your code here. Sleep is used to mimic operation time.
    print('Running my_func for {}s'.format(s))
    time.sleep(s)
    print('my_func complete {}s'.format(time.time()-t0))
    e.set()

def timeout_func(s):  # Controls timeout
    print('Starting timeout_func for {}s'.format(s))
    time.sleep(s)
    print('timeout_func complete {}s'.format(time.time()-t0))
    e.set()

t0 = time.time()
q = queue.Queue()
myfunc_runtime = 5  # Mimics the amount of time your function runs
timeout_threshold = 10  # Seconds until timeout

# Initialize and start threads
thread_timeout = threading.Thread(target=timeout_func, args=[timeout_threshold])
thread_myfunc = threading.Thread(target=my_func, args=[myfunc_runtime])
thread_timeout.daemon = True  # Essential for event to stop thread
thread_myfunc.daemon = True  # Essential for event to stop thread
e = threading.Event()
thread_timeout.start()
thread_myfunc.start()

# Wait until your event is set. Script completion time is always the minimum of runtime for both funcs
e.wait()
print('Script completion time: ' + str(time.time()-t0))

Upvotes: 0

TheLogicGuy
TheLogicGuy

Reputation: 690

For Linux you can use the kill() command and pass the current process' ID and the SIGINT signal to start the steps to exit the app.

import signal

os.kill(os.getpid(), signal.SIGINT)

Upvotes: 4

GR Tech School
GR Tech School

Reputation: 81

The easiest way to exit the whole program is, we should terminate the program by using the process id (pid).

import os
import psutil

current_system_pid = os.getpid()

ThisSystem = psutil.Process(current_system_pid)
ThisSystem.terminate()

To install psutl:- "pip install psutil"

Upvotes: 7

Nagasaki45
Nagasaki45

Reputation: 2850

Using thread.interrupt_main() may not help in some situation. KeyboardInterrupts are often used in command line applications to exit the current command or to clean the input line.

In addition, os._exit will kill the process immediately without running any finally blocks in your code, which may be dangerous (files and connections will not be closed for example).

The solution I've found is to register a signal handler in the main thread that raises a custom exception. Use the background thread to fire the signal.

import signal
import os
import threading
import time


class ExitCommand(Exception):
    pass


def signal_handler(signal, frame):
    raise ExitCommand()


def thread_job():
    time.sleep(5)
    os.kill(os.getpid(), signal.SIGUSR1)


signal.signal(signal.SIGUSR1, signal_handler)
threading.Thread(target=thread_job).start()  # thread will fire in 5 seconds
try:
    while True:
        user_input = raw_input('Blocked by raw_input loop ')
        # do something with 'user_input'
except ExitCommand:
    pass
finally:
    print('finally will still run')

Related questions:

Upvotes: 28

Alex Martelli
Alex Martelli

Reputation: 881665

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).

Upvotes: 71

Mark Rushakoff
Mark Rushakoff

Reputation: 258188

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.

Upvotes: 121

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