Aqui está um código de exemplo que responde à minha pergunta:
#!/usr/bin/python
# This is some example code on howto use dbus to detect when the system returns
#+from hibernation or suspend.
import dbus # for dbus communication (obviously)
import gobject # main loop
from dbus.mainloop.glib import DBusGMainLoop # integration into the main loop
def handle_resume_callback():
print "System just resumed from hibernate or suspend"
DBusGMainLoop(set_as_default=True) # integrate into main loob
bus = dbus.SystemBus() # connect to dbus system wide
bus.add_signal_receiver( # defince the signal to listen to
handle_resume_callback, # name of callback function
'Resuming', # singal name
'org.freedesktop.UPower', # interface
'org.freedesktop.UPower' # bus name
)
loop = gobject.MainLoop() # define mainloop
loop.run() # run main loop
Veja o tutorial do dbus-python .