Example on how to use python-dbus to receive notification of song changes

dbus_mpris_notify.py

#!/usr/bin/env python

import gobject
import dbus
import dbus.service
import dbus.mainloop.glib

def on_properties_changed(interface, props, invalidated_props):
    if "Metadata" in props:
        metadata = props.get("Metadata")
        artists = metadata.get("xesam:artist")
        title = metadata.get("xesam:title")
        album = metadata.get("xesam:album")
        track_num = metadata.get("xesam:trackNumber")

        print " Track: " + str(track_num)
        print "Artist: " + artists[0]
        print " Album: " + album
        print " Title: " + title
        print ""
        
if __name__ == "__main__":
    dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)

    player = dbus.SessionBus().get_object("org.mpris.MediaPlayer2.rhythmbox", "/org/mpris/MediaPlayer2")
    player.connect_to_signal("PropertiesChanged", on_properties_changed)

    loop = gobject.MainLoop()
    loop.run()