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pythonkeyboardinterrupt
Rolli
Rolli

Reputation: 41

Handle KeyboardInterrupt in the shell if no script is running

Is it possible to handle KeyboardInterrupt in the shell if no script is running?

The background of my question is the following: I use python to send commands to a motor controller via a socket connection. The function sends a target position of a motor to the controller and immediately returns, i.e. before the motor actually reaches its target position. Now it can happen that a user enters a wrong position and wants to interrupt the motor motion as quick as possible. This could be done by typing stop() which sends a stop command to the controller. But it would be more intuitive and faster if the motor could be stopped by pressing Ctrl+C. Is there a way to let python execute a function by pressing Ctrl+C while no script is running?

I know how to handle the KeyboardInterrupt exception or the signal.SIGINT within a running script, but could not find any hints on how to solve my goal.

I would be very grateful for any help!

Upvotes: 0

Views: 889

Answers (2)

James
James

Reputation: 36781

If the controller can handle having multiple connections to the socket, you can launch an entire new process that makes use of the keyboard module to listen for ctrl+c and then have that process send the stop command to controller.

First install the keyboard package from pypi

pip install keyboard

Create a file to listen for ctrl+c:

# file named 'wait_stop.py
##########################

import keyboard

# code here to establish connection to controller

def wait_stop():
    keyboard.wait('ctrl+c')
    print('sending stop signal')
    # function that sends stop signal here...
    # ...
    # call wait_stop again to continue listening.
    wait_stop()

if __name__ == '__main__':
    wait_stop()

Now you can launch the process in a separate shell via:

python wait_stop.py

As long as the wait_stop process shell is NOT the active window, hitting ctrl+c will cause send the stop() function to the controller. If the window is active, it will also kill the wait_stop.py process.

Upvotes: 1

Louis Saglio
Louis Saglio

Reputation: 1148

KeyboardInterrupt send SIGINT signal (code 2).

So instead of hitting CTRL+C you could send KeyboardInterrupt with kill -2 <pid>.

To display your program pid use os.getpid().

Upvotes: 0

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