[FIXED] What is the best way for a Python script to communicate with a Python Flask server that transports content to the client?

Issue

The following scenario:

I have a Raspberry Pi running as a server. Currently I am using a Python script with Flask and I can also access the Raspberry Pi from my PC. (The flask server runs an react app.)

But the function should be extended. It should look like the following:

2nd Python script is running all the time. This Python script fetches data from an external API every second and processes it. If certain conditions are met, the data should be processed and then the data should be communicated to the Python Flask server. And the Flask server then forwards the data to the website running on the computer.

How or which method is best to program this "interprocess communication". Are there any libraries? I tried Celery, but then it throws up my second Python script whenever I want to access the external API, so I don't know if this is the right choice.

What else would be the best approach? Threading? Direct interprocess communication?

If important, this is how my server application looks so far:

from gevent import monkey
from flask import Flask, render_template
from flask_socketio import SocketIO
monkey.patch_all()

app = Flask(__name__, template_folder='./build', static_folder='./build/static')
socket_io = SocketIO(app)


@app.route('/')
def main():
    return render_template('index.html')


@socket_io.on('fromFrontend')
def handleInput(input):
    print('Input from Frontend: ' + input)
    send_time()


@socket_io.on('time')
def send_time():
    socket_io.emit('time', {'returnTime': "some time"})


if __name__ == '__main__':
    socket_io.run(app, host='0.0.0.0', port=5000, debug=True)

Solution

Well i found a solution for my specific problem i implemented it with a thread as follows:

import gevent.monkey
gevent.monkey.patch_all()


from flask import Flask, render_template
from flask_socketio import SocketIO
import time
import requests
from threading import Thread


app = Flask(__name__, template_folder='./build', static_folder='./build/static')
socket_io = SocketIO(app)


@app.route('/')
def main():
    thread = Thread(target=backgroundTask)
    thread.daemon = True
    thread.start()
    return render_template('index.html')


@socket_io.on('fromFrontend')
def handleInput(input):
    print('Input from Frontend: ' + input)

@socket_io.on('time')
def send_time():
    socket_io.emit('time', {'returnTime': 'hi frontend'})


def backgroundTask():
    # do something here
    # access socket to push some data
    socket_io.emit('time', {'returnTime': "some time"})


if __name__ == '__main__':
    socket_io.run(app, host='0.0.0.0', port=5000, debug=True)

Answered By - Saboteur