When your facebook page recieves a message, the following code is used to extract the vital information from the message.

recieve_fb_data.py

@app.route('/', methods=['POST'])
def webhook():

    # endpoint for processing incoming messaging events

    data = request.get_json()
    log(data)  # you may not want to log every incoming message in production, but it's good for testing

    if data["object"] == "page":

        for entry in data["entry"]:
            for messaging_event in entry["messaging"]:

                if messaging_event.get("message"):  # someone sent us a message

                    sender_id = messaging_event["sender"]["id"]        # the facebook ID of the person sending you the message
                    recipient_id = messaging_event["recipient"]["id"]  # the recipient's ID, which should be your page's facebook ID
                    message_text = messaging_event["message"]["text"]  # the message's text