How do I change the qos level and message retain?

Hi I have some code for mqtt publish/subscribe in python. I want to change the qos value and message retain but I don't know how to because at the moment the qos value always only prints 0 and I want to change the message retain flag to either true or false and not 0. All help appreciated.

import paho.mqtt.client as mqtt
import time
class laser(mqtt.Client):
    def on_connect(self, mqttc, obj, flags, rc):
        print("rc: "+str(rc))
        print("Subscribing to topic","microscope/light_sheet_microscope/laser")
        mqttc.subscribe("microscope/light_sheet_microscope/laser")

    def on_message(self, mqttc, userdata, message):
        print("message received " ,str(message.payload.decode("utf-8")))
        print("message topic=",message.topic)
        print("message qos=",message.qos)
        print("message retain flag=",message.retain)

    def on_publish(self, mqttc, obj, mid):
        print("mid: "+str(mid))

    def on_subscribe(self, mqttc, obj, mid, granted_qos):
        print("Subscribed: "+str(mid)+" "+str(granted_qos))

    def on_log(self, mqttc, userdata, level, buf):
        print("log: ",buf)

    def run(self):
        self.connect("broker.hivemq.com", 1883, 60)

print("creating new instance")
client = laser("Laser")
client.run()

client.loop_start() #start the loop
time.sleep(2)
print("Publishing message to topic","microscope/light_sheet_microscope/laser")
client.publish("microscope/light_sheet_microscope/laser","Hello World Im a laser!")
time.sleep(2) # wait
client.loop_stop() #stop the loop

Thanks

Solution

From the Paho Python docs

PUBLISH()

publish(topic, payload=None, qos=0, retain=False)

This causes a message to be sent to the broker and subsequently from the broker to any clients subscribing to matching topics. It takes the following arguments:

topic the topic that the message should be published on

payload the actual message to send. If not given, or set to None a zero length message will be used. Passing an int or float will result in the payload being converted to a string representing that number. If you wish to send a true int/float, use struct.pack() to create the payload you require

qos the quality of service level to use

retain if set to True, the message will be set as the “last known good”/retained message for the topic.

To set QOS to 2 and the retained flag to true change the publish line to the following:

client.publish("microscope/light_sheet_microscope/laser","Hello World Im a laser!",2,True)