Heroku Cannot Work With My Python Script

I'm new to python and flask. The flask's document says you can deploy your app to heroku for public access. So I turned to heroku site. I followed the getting started guide step by

Solution 1:

The problem is with your Procfile.

web:gunicorn app:app

This tells gunicorn to run the WSGI application named app that can be found in a module or package named app. Your module, however, is named index.

You can either rename index.py to app.py or change the contents of your Procfile to

web:gunicorn index:app