Powers on the bluetooth adapter, connects to the headset and sets it as the default PulseAudio sink.

pabt-raindance.py

#!/usr/bin/env python3
# Powers on the bluetooth adapter, connects to the headset and sets it as
# the default PulseAudio sink.
#
# Released into the public domain.
# http://creativecommons.org/publicdomain/zero/1.0/

from sys import stderr
from gi.repository import GLib, Gio
from subprocess import Popen

CONTROLLER_MAC = None
HEADSET_MAC = "00:11:22:33:44:55"

OBJMAN = "org.freedesktop.DBus.ObjectManager"
DBPROP = "org.freedesktop.DBus.Properties"
BLZDEV = "org.bluez.Device1"
ADPDEV = "org.bluez.Adapter1"

def BTHeadsetRaindance():
	headsetMacUnderscores = HEADSET_MAC.replace(":", "_")
	headsetMacEnd = "/dev_" + headsetMacUnderscores
	headsetPath = None

	bus = Gio.bus_get_sync(Gio.BusType.SYSTEM, None)
	bluezObjman = Gio.DBusProxy.new_sync(
		bus, Gio.DBusProxyFlags.NONE, None, 'org.bluez', '/', OBJMAN,
		None
	)
	managedObjects = bluezObjman.GetManagedObjects('()')
	for obj in managedObjects.keys():
		if obj.endswith(headsetMacEnd):
			headsetPath = obj

	if headsetPath is None:
		print("Headset device not found!", file=stderr)
		return

	# power to the controller
	controllerPath = headsetPath[:headsetPath.rindex("/")]
	controllerProxy = Gio.DBusProxy.new_sync(
		bus, Gio.DBusProxyFlags.NONE, None, 'org.bluez', controllerPath,
		DBPROP, None
	)
	controllerProxy.Set(
		'(ssv)', ADPDEV, 'Powered', GLib.Variant.new_boolean(True)
	)

	# connect the headset
	headsetProxy = Gio.DBusProxy.new_sync(
		bus, Gio.DBusProxyFlags.NONE, None, 'org.bluez', headsetPath,
		BLZDEV, None
	)
	headsetProxy.Connect('()')

	# tell PulseAudio to use it by default
	Popen([
		"pactl", "set-default-sink",
		"bluez_sink.{0}".format(headsetMacUnderscores)
	]).wait()

if __name__ == '__main__':
	BTHeadsetRaindance()