This tutorial is adapted from a forum post answered by Krydos, How do I use Flask on the HelioNet forum.
It is worth to note that flask on the Tommy and Johnny servers use python 3.7, and if you want to use flask on python 2.7 you have to be on the Ricky server.
About Flask
Flask is a Python web framework built with a small core and easy-to-extend philosophy. Full Stack Python
Create a file named flask.wsgi in the flask directory.
import os, sys
# edit your username below
sys.path.append("/home/username/public_html/flask")
sys.path.insert(0, os.path.dirname(__file__))
from myapp import app as application
# make the secret code a little better
application.secret_key = 'secret'
Create a python script named myapp.py in the flask directory.