If I have a thread in an infinite loop, is there a way to terminate it when the main program ends (for example, when I press Ctrl+C)?
Check this question. The correct answer has great explanation on how to terminate threads the right way:
Is there any way to kill a Thread in Python?
To make the thread stop on Keyboard Interrupt signal (ctrl+c) you can catch the exception “KeyboardInterrupt” and cleanup before exiting. Like this:
try: start_thread() except (KeyboardInterrupt, SystemExit): cleanup_stop_thread() sys.exit()
This way you can control what to do whenever the program is abruptly terminated.
You can also use the built-in signal module that lets you setup signal handlers (in your specific case the SIGINT signal): http://docs.python.org/library/signal.html
If you make your worker threads daemon threads, they will die when all your non-daemon threads (e.g. the main thread) have exited.
Use the atexit module of Python’s standard library to register “termination” functions that get called (on the main thread) on any reasonably “clean” termination of the main thread, including an uncaught exception such as
KeyboardInterrupt. Such termination functions may (though inevitably in the main thread!) call any
stop function you require; together with the possibility of setting a thread as
daemon, that gives you the tools to properly design the system functionality you need.
If you spawn a Thread like so –
myThread = Thread(target = function) – and then do
myThread.start(); myThread.join(). When CTRL-C is initiated, the main thread doesn’t exit because it is waiting on that blocking
myThread.join() call. To fix this, simply put in a timeout on the .join() call. The timeout can be as long as you wish. If you want it to wait indefinitely, just put in a really long timeout, like 99999. It’s also good practice to do
myThread.daemon = True so all the threads exit when the main thread(non-daemon) exits.
from threading import Thread t = Thread(target=desired_method) t.daemon = True # Dies when main thread (only non-daemon thread) exits. t.start()
t = Thread(target=desired_method, daemon=True).start()
When your main thread terminates (e.g. Ctrl+C keystrokes), other threads will also be killed by the instructions above.
Daemon threads are killed ungracefully so any finalizer instructions are not executed.
A possible solution is to check is main thread is alive instead of infinite loop.
E.g. for Python 3:
while threading.main_thread().isAlive(): do.you.subthread.thing() gracefully.close.the.thread()