Htykuut

I have written the following testing code for a website. The index shows a relatively empty page, but it'll open a stream from which it can receive more messages from the server, effectively allowing me to make server side events. For this, I need to insert a generator into the Response object.

from flask import Flask, Response, render_template



app = Flask(__name__)



def answer():

    while True:

        q = input("Whaddaya wanna say? ")

        yield 'data: {} nn'.format(q)



@app.route('/')

def index():

    return render_template('index.html')



@app.route('/stream')

def stream():

    return Response(answer(), mimetype="text/event-stream")



if __name__ == "__main__":

    app.run(threaded=True, debug=True)

Together with a file called index.html, this works perfectly fine. I am receiving any text that I have given as an input to the terminal. However, if a second user were to visit the server, Python starts going back and forth between the two users - some input will be sent to one user, the next will always be sent to the other. I understand that this is how it's supposed to work, but I wondered if it was possible to create a generator that would yield to all clients.

Currently, I could think of two possible ways to do this. The first one isn't too complicated, but I'm not sure if it's a good idea to put in practice. Here, one Messenger instance would be created, after which its ànswer() function would be given as a generator.

class Messenger:

    def __init__(self):

        self.message = ""

    def send_msg(self,msg):

        self.message = msg



    def answer(self):

        current_message = self.message

        while True:

            # Yield when the message has been updated

            if self.message != current_message:

                current_message = self.message

                yield current_message

I do not really like this code for two reasons. First off, it does not allow the user to send the same message twice in a row. Second, checking constantly seems like wasting a lot of time on checking stuff. There has to be a better way. Is there?

I have been trying multiple methods, but I just can't think of any. I couldn't find any solution on the internet either. My current guess is to somehow make the function wait until the update is made. Something like the following, though I wouldn't know how to finish this code.

class Messenger:

    def __init__(self):

        self.message = ""

    def send_msg(self,msg):

        self.message = msg



    def answer(self):

        while True:

            pass # Pause function until send_msg() is executed



            yield self.message

Is it possible to create such a function? Is there a better way to solve this issue? Would you instead recommend looking into finding an alternative to the generator? Is the first option not as bad as it seems, and if so, why?