kill-process.py

#!/usr/bin/env python
"""
- read output from a subprocess in a background thread
- show the output in the GUI
- stop subprocess using a Tkinter button

https://stackoverflow.com/questions/15362372/display-realtime-output-of-a-subprocess-in-a-tkinter-widget
"""
from __future__ import print_function
import sys
from subprocess import Popen, PIPE, STDOUT
from textwrap import dedent
from threading import Thread

try:
    import Tkinter as tk
except ImportError:
    import tkinter as tk  # Python 3

info = print


class StopProcessDemo:
    def __init__(self, root):
        self.root = root

        # show subprocess' stdout in GUI
        self._var = tk.StringVar()  # put subprocess output here
        tk.Label(root, textvariable=self._var).pack()

        # to access event's .data use tcl to bind the event
        # https://stackoverflow.com/questions/41912004/how-to-use-tcl-tk-bind-function-on-tkinters-widgets-in-python
        on_reading_line = root.register(self._var.set)
        root.tk.call("bind", root, '<<line>>', on_reading_line + " %d")

        # stop subprocess using a button
        tk.Button(root, text="Stop subprocess", command=self.stop).pack()

        for t in range(1):
            # start dummy subprocess to generate some output
            self.process = Popen([sys.executable, "-u", "-c", dedent("""
            import itertools, sys, time

            for i in itertools.count():
                print(i, sys.argv[1])
                time.sleep(0.1)
            """), str(t)], stdout=PIPE, stderr=STDOUT, universal_newlines=True)

            # launch thread to read the subprocess output:
            #   process.readline -> event <<line>> -> label
            t = Thread(target=self.reader_thread,
                       # https://mail.python.org/pipermail/tkinter-discuss/2013-November/003526.html
                       args=[lambda line: root.event_generate('<<line>>', when='tail', data=line)])
            t.daemon = True  # close pipe if GUI process exits
            t.start()

    def reader_thread(self, emit):
        """Read subprocess output and emit lines."""
        with self.process.stdout as pipe:
            for line in iter(pipe.readline, ''):
                emit(line)

    def stop(self):
        """Stop subprocess and quit GUI."""
        info('stoping')
        self.process.terminate()  # tell the subprocess to exit

        # kill subprocess if it hasn't exited after a countdown
        def kill_after(countdown):
            if self.process.poll() is None:  # subprocess hasn't exited yet
                countdown -= 1
                if countdown < 0:  # do kill
                    info('killing')
                    self.process.kill()  # more likely to kill on *nix
                else:
                    self.root.after(100, kill_after, countdown)
                    return  # continue countdown
            # clean up
            self.process.stdout.close()  # close fd
            self.process.wait()          # wait for the subprocess' exit
            self.root.destroy()       # exit GUI
        kill_after(countdown=5)


root = tk.Tk()
app = StopProcessDemo(root)
root.protocol("WM_DELETE_WINDOW", app.stop)  # exit subprocess if GUI is closed
root.mainloop()
info('exited')

God bless you! I'm working on my first python project with a limited coding background. After weeks of researching the possible methods to stream live data to my graph while keeping it interactive, I think this is the winner.