How do I use a function with a parameter not previously defined

Question

I'm using Alpaca's API with websocket to get stock price data. I want to use the variable position outside the function on_message but message is not previously defined so I get an error when I run the code name message is not defined

def on_message(ws, message):
    global position
    json.loads(message)
    position = (message[0]['bp'])

import websocket, json

def on_open(ws):

    print("opened")
    auth_data = {
        "action": "auth", "key": <API_KEY>, "secret": <API_SECRET>
    }
    ws.send(json.dumps(auth_data))

    listen_message = {"action":"subscribe","quotes":["AAPL"]}

    ws.send(json.dumps(listen_message))

def on_message(ws, message):
    global position
    json.loads(message)
    position = (message[0]['bp'])

socket = "wss://stream.data.alpaca.markets/v2/iex"
             
ws = websocket.WebSocketApp(socket, on_open=on_open, on_message=on_message)
ws.run_forever()

sorry if this is a badly worded question it's about 1 am and im tired.