Learn to use Flask with Python 3 to make a RESTful API in Fewer than 10 Minutes
I use this demo code in a lot of videos. To use it, clone it, then set up a virtual environment, activate it, and install flask with pip.
pip install flask
To run it, you need to either set the FLASK_APP environment variable, which is the subject of this video:
Or, you need to supply the file name containing the app:
flask run mds-flask-demo.py