python MQTT wrapper

mqtt.py

import thread, mosquitto, random, time
# mosquitto reference and download can be found here: http://mosquitto.org/documentation/python/

class mqtt():    
    def __init__(self, broker = "127.0.0.1", port = 1883, clientID = None):
        self.__broker = broker
        self.__port = port
        self._client = None
        self.__subscriptionsList = []
        self.__pendingSubscriptionsList = []
        self.__pendingUnsubscriptionsList = []
        self.__publishQueue = []
        self.__connected = False
        self.__tryToConnect = False
        self.clientID = clientID
        if self.clientID == None:
            self.clientID = "PythonMQTTClient" + str(random.randint(0, 1000))
    
    def subscribe(self, topic, QoS = 0):
        if(self.__connected):
            self._client.subscribe(topic, QoS)
            self.__subscriptionsList.append(topic)
            print "Subscribing to " + topic
        else:
            self.__pendingSubscriptionsList.append((topic, QoS))
            print "Client is not connected at the moment. Will subscribe on connection"
    
    def unsubscribe(self, topic):
        if(self.__connected):
            self.__subscriptionsList.remove(topic)
            self._client.unsubscribe(topic)
            print "Unsubscribing from " + topic
        else:
            self.__pendingUnsubscriptionsList.append(topic)
            print "Client is not connected at the moment. Will unsubscribe on connection"
            
    def publish(self, topic, message, QoS = 0, retain = False):
        self.__publishQueue.append((topic, message, QoS, retain));
    
    # override this methods to add your functionality
    def on_connect(self, obj, rc):
#        print "on_connect",obj, rc
        pass
    
    def on_disconnect(self, obj, rc):
#        print "on_disconnect"
        pass
            
    def on_subscribe(self, obj, mid, qos_list):
#        print "on_subscribe", mid, qos_list
        pass
        
    def on_unsubscribe(self, obj, mid):
#        print "on_unsubscribe", mid
        pass
    
    def on_publish(self, obj, mid):
#        print "on_publish", mid
        pass
            
    def on_message(self, obj, msg):
#        print "Message received on topic " + msg.topic + " with QoS " + str(msg.qos) + " and payload " + msg.payload
        pass

    # actual MQTT callbacks
    def __on_connect(self, mosquitto_instance, obj, rc):
        #rc 0 successful connect
        if rc == 0:
            print "MQTT Connected"
            self.__connected = True
            self.__tryToConnect = False
            while(len(self.__pendingSubscriptionsList) != 0):
                (topic, QoS) = self.__pendingSubscriptionsList.pop()
                print "executing pending subscription to " + topic + " with QoS " + str(QoS)
                self.subscribe(topic, QoS)
            while(len(self.__pendingUnsubscriptionsList) != 0):
                topic = self.__pendingUnsubscriptionsList.pop()
                print "executing pending unsubscription from " + topic
                self.unsubscribe(topic)
            self.on_connect(obj, rc)
        else:
            print "We have an error here.\nERROR CODE IS " + rc + "\nCleaning up ..."
            self.__cleanup()
                  
    def __on_disconnect(self, mosquitto_instance, obj, rc):
        self.__connected = False
        print "Disconnected successfully. Return Code:", rc
        self.on_disconnect(obj, rc)
            
    def __on_subscribe(self, mosquitto_instance, obj, mid, qos_list):
        self.on_subscribe(obj, mid, qos_list)
    
    def __on_unsubscribe(self,mosquitto_instance, mid):
        self.on_unsubscribe(obj, mid)
    
    def __on_publish(self, mosquitto_instance, obj, mid):
        self.on_publish(obj, mid)
    
    def __on_message(self, mosquitto_instance, obj, message):
        self.on_message(obj, message)

    #called on exit
    # disconnect MQTT and clean up subscriptions
    def __cleanup(self):
        print "Ending and cleaning up"
        while(len(self.__subscriptionsList) != 0):
                topic = self.__subscriptionsList[0]
                self.unsubscribe(topic)
        self._client.disconnect()
    
    def loop(self):
        print "starting mqtt loop"
        try:
		while self._client.loop(10) == 0:
                	while self.__publishQueue: # if publish queue is not empty
                    		(topic, message, QoS, retain) = self.__publishQueue.pop(0)
                    		self._client.publish(topic, message, QoS, retain)
        except Exception as e:
		print "connection lost. try to restart", e
        self._client.connect(self.__broker, self.__port, 60)
        self.__tryToConnect = True
        thread.start_new_thread(self.loop, ())
    
    def startMQTT(self):
        self._client = mosquitto.Mosquitto(self.clientID)
        #attach MQTT callbacks
        self._client.on_connect = self.__on_connect
        self._client.on_disconnect = self.__on_disconnect
        self._client.on_subscribe = self.__on_subscribe
        self._client.on_unsubscribe = self.__on_unsubscribe
        self._client.on_publish = self.__on_publish
        self._client.on_message = self.__on_message

        #connect to broker
        self.__tryToConnect = True
        if(self._client.connect(self.__broker, self.__port, 60) != 0):
            raise Exception("Can't connect to broker")

        thread.start_new_thread(self.loop, ())
            
    def stopMQTT(self):
        self.__cleanup()