bus = dbus.Bus (dbus.Bus.TYPE_SYSTEM)
hal_service = bus.get_object ('org.freedesktop.Hal', '/org/freedesktop/Hal')
hal_manager_obj = bus.get_object('org.freedesktop.Hal', '/org/freedesktop/Hal/Manager')
hal_manager = dbus.Interface(hal_manager_obj, 'org.freedesktop.Hal.Manager')

device_list = hal_manager.GetAllDevices()
for udi in device_list:
   device = hal_service.get_object ('org.freedesktop.Hal.Device', udi)