Passing data received from a json request to another function in python flask socketio

Question

I have a python flask app which receives data from json. I have also used socketio and threading in order to process data realtime. In my program I need to send the data, that I receive from json requests, to another python function. Below is the code that I wrote to do this: -

from flask_socketio import SocketIO, emit
from flask import Flask, render_template, request, url_for, copy_current_request_context
from random import random
from time import sleep
from pygeodesy.ellipsoidalVincenty import LatLon
from threading import Thread, Event

__author__ = 'shark'

app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret!'
app.config['DEBUG'] = True

# turn the flask app into a socketio app
socketio = SocketIO(app, async_mode=None, logger=True, engineio_logger=True)

# random number Generator Thread
thread = Thread()
thread_stop_event = Event()


@app.route('/platform-data', methods=['POST'])
def platformData():
    """
    Generate a random number every 1 second and emit to a socketio instance (broadcast)
    Ideally to be run in a separate thread?
    """
    # infinite loop of magical random numbers
    print("Receiving platform data")
    while not thread_stop_event.isSet():
        req_data = request.get_json()

        id = req_data['id']
        latitude = req_data['coordinates'][1]
        longitude = req_data['coordinates'][0]
        speed = req_data['speed']
        angle = req_data['angle']
        length = req_data['dimensions'][0]
        width = req_data['dimensions'][1]
        laneW = req_data['lane_width']
        spdLmt = req_data['speed_limit']

        return testProcess(speed)


        def testProcess(speed):
            if speed>30:
                print("slow down")


        socketio.emit('speed', {'speed': speed}, namespace='/test')
        socketio.sleep(.5)


@app.route('/')
def index():
    # only by sending this page first will the client be connected to the socketio instance
    return render_template('index.html')


@socketio.on('connect', namespace='/test')
def test_connect():
    # need visibility of the global thread object
    global thread
    print('Client connected')

    # Start the random number generator thread only if the thread has not been started before.
    if not thread.isAlive():
        print("Starting Thread")
        thread = socketio.start_background_task(platformData)


@socketio.on('disconnect', namespace='/test')
def test_disconnect():
    print('Client disconnected')


if __name__ == '__main__':
    socketio.run(app)

However, when I run the app and POST data from Postman, I get the below error in my console: -

TypeError: The view function did not return a valid response. The return type must be a string, dict, tuple, Response instance, or WSGI callable, but it was a int. 127.0.0.1 - - [05/Mar/2020 17:06:25] "POST /platform-data HTTP/1.1" 500 15625 0.008975

I know the reason for this is that I have declared return testProcess(speed).

Therefore, I need to know the correct way to pass speed variable to 'testProcess' function.

Answer 1

platformData() must return a a string, dict, tuple, Response instance, or WSGI callable but you make return the return of testProcess which is not defined try:

 def testProcess(speed):
        if speed>30:
            return "slow down"
        else:
            return "ok"

Or just call testProcess(speed) without return and then return something else