How can I avoid to use global variables? (python - flask-socketio app)

Question

I'm trying to figure out how to not use global variables for my application but I can't think of anything else.

I'm actually coding a web interface with the help of the Flask-SocketIO module to interact in real time with a music player.

This is a snippet of my code containing the play function (I think I only need one example and then I can adapt it for all the other functions):

from flask import Flask, render_template
from flask_socketio import SocketIO

app = Flask(__name__)
socketio = SocketIO(app)
isPlaying = False #This is the variable that I would like to avoid making global

@socketio.on('request_play')
def cycle_play():
    global isPlaying
    if isPlaying == True:
        socketio.emit('pause', broadcast=True)
        isPlaying = False
    else:
        socketio.emit('play', broadcast=True)
        isPlaying = True

if __name__ == '__main__':
    socketio.run(app, port=5001)

This is only a stripped down version of the code but I think it's enough to understand what I'm trying to accomplish.

I need to access that variable also from other functions and I need to do the same with the song name, duration and current time.

Thanks in advance for the help and sorry if my English is not clear.

---

Here is the solution that I used:

from flask import Flask, render_template
from flask_socketio import SocketIO

app = Flask(__name__)
socketio = SocketIO(app)

class Player():
    def __init__(self):
        self.isPlaying = False


    def cycle_play(self):
        if self.isPlaying == True:
            socketio.emit('pause', broadcast=True)
            self.isPlaying = False
        else:
            socketio.emit('play', broadcast=True)
            self.isPlaying = True


if __name__ == '__main__':
    player = Player()
    socketio.on('request_play')(player.cycle_play) #this is the decorator
    socketio.run(app, port=5001)

Answer 1

You can use the user session to store such values. You can read up more about the session object here: flask.pocoo.org/docs/0.12/quickstart/#sessions.

from flask import session

@socketio.on('initialize')
def initialize(isPlaying):
    session['isPlaying'] = isPlaying

@socketio.on('request_play')
def cycle_play():
    # Note, it's good practice to use 'is' instead of '==' when comparing against builtin constants.
    # PEP8 recommended way is to check for trueness rather than the value True, so you'd want to first assert that this variable can only be Boolean.
    assert type(session['isPlaying']) is bool

    if session['isPlaying']: 
        socketio.emit('pause', broadcast=True)
        session['isPlaying'] = False
    else:
        socketio.emit('play', broadcast=True)
        session['isPlaying'] = True