show-subprocess-output-io-watch.py

#!/usr/bin/python
from subprocess import Popen, PIPE

from gi.repository import GObject, Gtk

# create GUI to show subprocess output
win = Gtk.Window()
win.set_default_size(640, 480)
label = Gtk.Label('process output')
win.add(label)

# start dummy subprocess to generate some output
proc = Popen(["python", "-u", "-c", """import itertools, sys, time
for i in itertools.count():
    print(i)
    sys.stderr.write(".") # show that we are alive in terminal
    time.sleep(0.5)
"""], stdout=PIPE)

# read from subprocess
def read_data(source, condition):
    line = source.readline() # might block
    if not line:
        source.close()
        return False # stop reading
    # update text
    label.set_text('Subprocess output: %r' % (line.strip(),))
    return True # continue reading
io_id = GObject.io_add_watch(proc.stdout, GObject.IO_IN, read_data)

# exit subprocess if GUI is closed
def quit(win, event, proc):
    GObject.source_remove(io_id) # stop watching
    proc.terminate()

    # kill subprocess if it hasn't exited in timeout seconds
    timeout = 5
    def poll(proc, countdown):
        if proc.poll() is None: # subprocess hasn't exited yet
            countdown[0] -= 1
            if countdown[0] <= 0:
                proc.kill()
                proc.wait()
                Gtk.main_quit()
            else:
                return True # continue polling
        else: # subprocess exited
            Gtk.main_quit()
    # call poll() once a second
    GObject.timeout_add(1000, poll, proc, [timeout])

win.connect('delete-event', quit, proc)

win.show_all()
Gtk.main()

show-subprocess-output-thread.py

#!/usr/bin/python
from contextlib import closing
from threading import Thread
from subprocess import Popen, PIPE

from gi.repository import GObject, Gtk
GObject.threads_init()  # all Gtk is in the main thread;
                        # only GObject.idle_add() is in the background thread

# create GUI to show subprocess output
win = Gtk.Window()
win.set_default_size(640, 480)
label = Gtk.Label('process output')
win.add(label)

# start dummy subprocess to generate some output
proc = Popen(["python", "-u", "-c", """import itertools, sys, time
for i in itertools.count():
    print(i)
    sys.stderr.write(".") # show that we are alive in terminal
    time.sleep(0.5)
"""], stdout=PIPE)

# read from subprocess in a separate thread
def reader_thread(proc, update_text):
    with closing(proc.stdout) as file:
        for line in iter(file.readline, b''):
            # execute update_text() in GUI thread
            GObject.idle_add(update_text, 'Subprocess output: %r' % (
                    line.strip(),))

t = Thread(target=reader_thread, args=[proc, label.set_text])
t.daemon = True # exit with the program
t.start()

# exit subprocess if GUI is closed
def quit(win, event, proc):
    proc.terminate()

    # kill subprocess if it hasn't exited in timeout seconds
    timeout = 5
    def poll(proc, countdown):
        if proc.poll() is None: # subprocess hasn't exited yet
            countdown[0] -= 1
            if countdown[0] <= 0:
                proc.kill()
                proc.wait()
                Gtk.main_quit()
            else:
                return True # continue polling
        else: # subprocess exited
            Gtk.main_quit()
    # call poll() once a second
    GObject.timeout_add(1000, poll, proc, [timeout])

win.connect('delete-event', quit, proc)

win.show_all()
Gtk.main()