pyScss
A Sass compiler for Python
pyScss is a pure-Python implementation of the Sass language, the CSS superset that adds variables, nesting, mixins, and functions. I started it in 2011, back when “compile your CSS” meant shelling out to a Ruby toolchain and Node wasn’t really on the table for a Python shop. pyScss let a Python web stack compile Sass in-process, and for a stretch it was the de-facto Sass compiler in that ecosystem.
It covered most of what people actually used: roughly 95% of Sass 3.2 and a good chunk of Compass, MIT-licensed, running on Python 2 and 3 and PyPy. It’s around 586 stars now and mostly dormant. The world has moved on to libsass and Dart Sass, which is exactly what you want to happen to a piece of infrastructure: it did its job for the years it was needed.