Python API - How to get data from the uplink_callback method?

Application Development
1

Hi,

I’m currently trying to get a copy of the UplinkMessage object from the uplink_callback method to process some values in some kind of endless loop with the Python API.
My code looks something like this:

import time
import ttn
import csv
import os, sys
import queue

#Configuration data
app_id = "------------------------"
access_key = "--------------------"

message_path = os.path.abspath(os.path.dirname(sys.argv[0]))
message_path += '/messages.csv'


last_message = queue.Queue() #initialises a first in first out queue

#Define uplink method
def uplink_callback(msg, client):
    #Create CSV file with message content
    with open (message_path,'a',newline='') as message_file:
        csv_writer=csv.writer(message_file)
        csv_writer.writerow([msg.app_id,msg.dev_id,msg.payload_raw,msg.payload_fields.altitude,msg.payload_fields.hdop,msg.payload_fields.latitude,msg.payload_fields.longitude,msg.metadata.time])
        csv_writer.close()
    global last_message
    last_message.put((msg))




#Create handler for "The Things Network"
handler = ttn.HandlerClient(app_id, access_key, discovery_address="discovery.thethings.network:1900")


#Start mqtt client
mqtt_client = handler.data()
mqtt_client.set_uplink_callback(uplink_callback)
mqtt_client.connect()


while True:
    time.sleep(10)
    if not last_message.empty():
        print(last_message.get())

Despite the “last_message” queue is flagged as global in the uplink_callback method, I wasn’t able to show the data in the endless loop.
Does anyone has an answer to this issue?

2

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