C$50 Finance, a web app via which you can manage portfolios of stocks. Very small and simple, written in Flask. It's one of the projects from the Harvard's CS50 online course.
As a database it uses a module from the CS50 course itself called just 'SQL' which works with a very lightweight SQLite3 database.
For the stock's data the app connects to IEX API
As the frontend, it uses the 'Lux' theme from Bootswatch
The app file has a lot of comments explaining what the code does, although they are in spanish.