1.c

topic = "user/path/topic"

2.c

from Pubnub import Pubnub

def callback(message, channel):
    print(message, channel)

pubnub = Pubnub('demo', 'demo')
pubnub.subscribe('my_channel', callback=callback)

3.c

import paho.mqtt.client as mqtt

def on_message(client, userdata, message):
    print(msg.topic, str(msg.payload))

def on_connect(client, userdata, flags, rc):
    client.subscribe('my_topic')

client = mqtt.Client()
client.on_message = on_message
client.on_connect = on_connect
client.connect('mqtt.pubnub.com', 1883)
client.loop_forever()