RA is a simple relational algebra interpreter written in Python 3. It is built on top of an SQL-based relational database system. It implements relational algebra queries by translating them into SQL and executing them on the underlying database system through SQLAlchemy. RA is packaged with SQLite, so you can use RA as a standalone relational-algebra database system. Alternatively, you can use RA as a relational-algebra front-end to connect to other database servers from various vendors.
You can follow the project on GitHub, or read its documentation here.