import paho.mqtt.client as mqtt
def on_message(client, userdata, msg):
    print 'Received: ' + msg.payload

client = mqtt.Client()
client.on_message = on_message

client.connect('localhost', 1883)
client.subscribe('hello/#')

client.loop_forever()

import paho.mqtt.client as mqtt

client = mqtt.Client()

client.will_set('hello/will', 'Last will', 0, False)
client.connect('localhost', 1883)

client.publish('hello/world', 'Regular msg', 0, False)
client.disconnect()

Received: Last will