I managed to publish and I can see the changes of the button at Adafruit but I cannot subscribe. I want to control the led at lopy to switch on and off at Adafruit.

the coding for mqtt.py follow exactly same as the code in github, sometimes I get the error "subscribe callback is not set"

mqtt.py

def subscribe(self, topic, qos=0):
        assert self.cb is not None, "Subscribe callback is not set"
        pkt = bytearray(b"\x82\0\0\0")
        self.pid += 1
        struct.pack_into("!BH", pkt, 1, 2 + 2 + len(topic) + 1, self.pid)
        #print(hex(len(pkt)), hexlify(pkt, ":"))
        self.sock.write(pkt)
        self._send_str(topic)
        self.sock.write(qos.to_bytes(1, "little"))
        while 1:
            op = self.wait_msg()
            if op == 0x90:
                resp = self.sock.read(4)
                #print(resp)
                assert resp[1] == pkt[2] and resp[2] == pkt[3]
                if resp[3] == 0x80:
                    raise MQTTException(resp[3])
                return

main.py coding from alex's corner
https://www.youtube.com/watch?v=3NDPSbr5J14&t=997s

def settimeout(duration): 
   pass

def sub_cb(topic, msg): 
   print(msg)

client = MQTTClient(client_id="xxx", server="io.adafruit.com",user="xxx",
password="xxx", port=1883) 
client.settimeout=settimeout
client.set_callback(sub_cb)

client.connect()
print("connected to broker\n")
client.publish(topic="vickyho/feeds/lights",msg="False")
print("Published!")
time.sleep(10)
client.subscribe(topic="vickyho/feeds/lights")
print("Subscribed!")

while True:
     client.check_msg()
     if client.subscribe(topic="vickyho/feeds/digital",msg="ON")  
          pycom.rgbled(0xff00)
          print("Led ON")
          time.sleep(3)

     if client.subscribe(topic="vickyho/feeds/digital",msg="OFF")
          pycom.heartbeat(False)  
          pycom.rgbled(0x0000)
          print("Led OFF")
          time.sleep(3)

here is the error:

  File "main.py", line 40
SyntaxError: invalid syntax

line 40 is at pycom.rgbled(0xff00)

Can anyone help? Im new to python language so I dont know how to code. Thanks!

The main.py code you posted above is only 31 lines line

Here is the whole main.py

from network import WLAN
from mqtt import MQTTClient
import machine
import time
import pycom

#from machine import Pin
#pin=Pin('P10',mode=Pin.IN, pull=Pin.PULL_UP)

wlan = WLAN(mode=WLAN.STA)
wlan.antenna(WLAN.EXT_ANT)
wlan.connect("xxx", auth=(WLAN.WPA2, "xxx"), timeout=5000)

while not wlan.isconnected(): 
     machine.idle()
print("Connected to Wifi\n")

def settimeout(duration): 
   pass

def sub_cb(topic, msg): 
   print(msg)

client = MQTTClient(client_id="xxx", server="io.adafruit.com",user="vickyho",
                    password="xxx", port=1883) 
client.settimeout=settimeout
client.set_callback(sub_cb)

client.connect()
print("connected to broker\n")
client.publish(topic="vickyho/feeds/lights",msg="False")
print("Published!")
time.sleep(10)
client.subscribe(topic="vickyho/feeds/lights")
print("Subscribed!")

while True:
     client.check_msg()
     if client.subscribe(topic="vickyho/feeds/digital",msg="ON")  
          pycom.rgbled(0xff00)
          print("Led ON")
          time.sleep(3)

     if client.subscribe(topic="vickyho/feeds/digital",msg="OFF")
          pycom.heartbeat(False)  
          pycom.rgbled(0x0000)
          print("Led OFF")
          time.sleep(3)

thanks for your reply btw!