How to terminate a thread when main program ends

Question

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

User · Answer

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

User · Answer

Try with enabling the sub-thread as daemon-thread   For Instance   Recommended   from threading import Thread  t   Thread target  lt your-method gt   t daemon   True    This thread dies when main thread  only non-daemon thread  exits  t start     Inline   t   Thread target  lt your-method gt   daemon True  start     Old API   t setDaemon True  t start       When your main thread terminates   i e  when I press Ctrl C    other threads will also be killed by the instructions above

User · Answer

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

User · Answer

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

User · Answer

If you make your worker threads daemon threads  they will die when all your non-daemon threads  e g  the main thread  have exited   http   docs python org library threading html threading Thread daemon

User · Answer

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     See Check if the Main Thread is still alive from another thread

[python] How to terminate a thread when main program ends?

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