Stopping a process pygtk

Question

I am trying to make a simple application to play and stop a midi file using pygtk.

Here's what I have so far :

import pygtk
pygtk.require('2.0')
import gtk
import subprocess


class Teacher:

    def __init__(self):

        window = gtk.Window(gtk.WINDOW_TOPLEVEL)
        window.set_size_request(400, 200)
        window.set_title("Music Teacher")
        window.connect("delete_event",
                   lambda w,e: gtk.main_quit())

        table = gtk.Table(4, 4, True)
        window.add(table)

        play = gtk.Button("Play")
        play.connect("clicked", self.clicked_play)
        play.show()

        stop = gtk.Button("Stop")
        stop.show()

        table.attach(play, 0, 1, 0, 1)
        table.attach(stop, 0, 1, 1, 2)

        window.show_all()

    def clicked_play(self, widget):
        subprocess.Popen(["timidity", "~/somefile.mid"])

    def main(self):
        gtk.main()
        return 0


Teacher().main()

Is there I can send interrupt from stop and delete_event to kill the process? Should I be using threads?

Answer 1

You can handle getting a SIGTERM , a Ctrl+C, or the stop button being pushed like this:

import pygtk
pygtk.require('2.0')
import gtk
import subprocess
import signal


class Teacher:

    def __init__(self):
        self.proc = None  # Initialize the handle to our subprocess
        window = gtk.Window(gtk.WINDOW_TOPLEVEL)
        window.set_size_request(400, 200)
        window.set_title("Music Teacher")
        window.connect("delete_event",
                   lambda w,e: gtk.main_quit())

        table = gtk.Table(4, 4, True)
        window.add(table)

        play = gtk.Button("Play")
        play.connect("clicked", self.clicked_play)
        play.show()

        stop = gtk.Button("Stop")
        stop.connect("clicked", self.clicked_stop)
        stop.show()

        table.attach(play, 0, 1, 0, 1)
        table.attach(stop, 0, 1, 1, 2)

        window.show_all()

    def clicked_play(self, widget):
        self.proc = subprocess.Popen(["timidity", "~/somefile.mid"])

    def clicked_stop(self, widget=None):
        if self.proc:
            self.proc.terminate()
            self.proc.wait()

    def handle_sigterm(self, *args):
        self.clicked_stop()
        sys.exit()

    def main(self):
        signal.signal(signal.SIGTERM, self.handle_sigterm)
        try:
            gtk.main()
        except KeyboardInterrupt:
            self.clicked_stop()
            raise
        return 0


Teacher().main()

We just save a reference to the Popen object we created in clicked_play , and then use that handle to send a SIGTERM to the process using the terminate instance method in click_stop . We then call wait (which should finish instantly, unless timidity doesn't close on SIGTERM ) to reap the terminated process (so it won't leave a zombie behind).

I also added a try / except around the call to gtk.main() so that clicked_stop will be called if you issue a Ctrl+C, and a SIGTERM handler that does the same, should that signal be received.