Question

The following program hangs the terminal such that it ignores Ctrl+C. This is rather annoying since I have to restart the terminal every time one of the threads hang.

Is there any way to catch the KeyboardInterrupt while waiting on an event?

import threading
def main():
    finished_event = threading.Event()
    startThread(finished_event)
    finished_event.wait()#I want to stop the program here
    print('done!')
def startThread(evt):
    """Start a thread that will trigger evt when it is done"""
    #evt.set()
if __name__ == '__main__':
    main()

Answer 1

Update: On the current Python 3 finished_event.wait() works on my Ubuntu machine (starting with Python 3.2). You don’t need to specify the timeout parameter, to interrupt it using Ctrl+C. You need to pass the timeout parameter on CPython 2.

Here’s a complete code example:

#!/usr/bin/env python3
import threading

def f(event):
    while True:
        pass
    # never reached, otherwise event.set() would be here

event = threading.Event()
threading.Thread(target=f, args=[event], daemon=True).start()
try:
    print('Press Ctrl+C to exit')
    event.wait()
except KeyboardInterrupt:
    print('got Ctrl+C')

There could be bugs related to Ctrl+C. Test whether it works in your environment.

---

^{Old polling answer:}

You could try to allow the interpreter to run the main thread:

while not finished_event.wait(.1): # timeout in seconds
    pass

If you just want to wait until the child thread is done:

while thread.is_alive():
    thread.join(.1)