Split MQTT messages to AWS IoT Core

Question

I am trying to send messages from multiple devices to the same iot/topic in AWS IoT Core using a python script. The script is below:

#!/usr/bin/python

# Lab 1 - Setting up.
# Make sure your host and region are correct.

import sys
import ssl
from AWSIoTPythonSDK.MQTTLib import AWSIoTMQTTClient
import json
import time

#Setup our MQTT client and security certificates
#Make sure your certificate names match what you downloaded from AWS IoT

mqttc = AWSIoTMQTTClient("1234")

#Make sure you use the correct region!
mqttc.configureEndpoint("Masked-ats.iot.us-west-2.amazonaws.com",8883)
mqttc.configureCredentials("./rootCA.pem","./privateKey.pem","./certificate.pem")

#Function to encode a payload into JSON
def json_encode(string):
        return json.dumps(string)

mqttc.json_encode=json_encode

#Declaring our variables
with open('flatdata.txt') as f:
    df = json.load(f)
message = df

#Encoding into JSON
message = mqttc.json_encode(message)

#This sends our test message to the iot topic
def send():
    mqttc.publish("iot/topic", message, 0)
    print "Message Published"


#Connect to the gateway
mqttc.connect()
print "Connected"

#Loop until terminated
while True:
    send()
    time.sleep(5)

mqttc.disconnect()
#To check and see if your message was published to the message broker go to the MQTT Client and subscribe to the iot topic and you should see your JSON Payload

My flat data file looks like this:

[
 {
  "timestamp": 1519516800,
  "condition": true,
  "id": 4
 },
 {
  "timestamp": 1519517100,
  "condition": true,
  "id": 2
 }
]

Right now, the code dumps the data from both id's as a single message payload. But, I want it to loop through the txt file and send one section at a time. Section being defined by {} and not by id (because I can have duplicate id's). Additionally, I need it to ignore the [] in my data file and send the data as a json payload.

Answer 1

Your code is already parsing and then re-encoding the JSON so the simplest approach is probably just iterate through the parsed array sending a message for each element i.e.:

import json 

messageJSON = """[
 {
  "timestamp": 1519516800,
  "condition": true,
  "id": 4
 },
 {
  "timestamp": 1519517100,
  "condition": true,
  "id": 2
 }
]"""

message = json.loads(messageJSON)
for payload in message:
  pubJson = json.dumps(payload)
  print("sending: ", pubJson) 
  # mqttc.publish("iot/topic", pubJson, 0)

Result:

sending:  {"timestamp": 1519516800, "condition": true, "id": 4}
sending:  {"timestamp": 1519517100, "condition": true, "id": 2}

If that is not what you are looking for then please provide an example of the output you need (but once the JSON has been parsed it's pretty easy to work with in Python and your question is really about processing JSON not MQTT/Paho/AWS).