glib main loop hangs after Popen

Question

I'm trying to build a script that logs the window title when a different window becomes active. This is what I have so far:

import glib
import dbus
from dbus.mainloop.glib import DBusGMainLoop

def notifications(bus, message):
    if message.get_member() == "event":
        args = message.get_args_list()
        if args[0] == "activate":
            print "Hello world"
            activewindow = Popen("xdotool getactivewindow getwindowname", stdout=PIPE, stderr=PIPE); 
            print activewindow.communicate()



DBusGMainLoop(set_as_default=True)

bus = dbus.SessionBus()
bus.add_match_string_non_blocking("interface='org.kde.KNotify',eavesdrop='true'")
bus.add_message_filter(notifications)

mainloop = glib.MainLoop()
mainloop.run()

However, something is apparently wrong with my Popen call, and glib seems to swallow the error. At least, that is what someone on a IRC channel told me. When I remove the Popen and activewindow.communicate() calls, everything keeps working and I get a message "Hello world!" printed in the shell whenever I switch to a new window.

With the Popen and communicate() calls, the script prints a single "Hello world" and hangs after that.

Does anyone know:

• How I can get a proper error message?
• What I'm doing wrong in my Popen call?

Thanks in advance!

Answer 1

I can't just comment... you haven't imported process module, or its members (Popen, PIPE).