If this webserver is only for testing and demoing purposes. You can use ngrok, a open source too that tunnels your http traffic.
Bascially ngrok creates a public URL (both http and https) and then tunnels the traffic to whatever port your Flask process is running on.
It only takes a couple minutes to set up. You first have to download the software. Then run the command
./ngrok http [port number your python process is running on]
It will then open up a window in terminal giving you both an http and https url to access your web app.