python3-flask binary package in Ubuntu Focal amd64

 Flask is a micro web framework for Python based on Werkzeug, Jinja 2 and good
 intentions. A minimal Flask application looks like that:
 .
   from flask import Flask
   app = Flask(__name__)
 .
   @app.route("/")
   def hello():
       return "Hello World!"
 .
   if __name__ == '__main__':
       app.run()
 .
 This package contains the Python 3.x module.

Source package