I was recently surprised to find that there are no free, easy-to-use Python grammar-checking libraries. I forked some old code that uses a LanguageTool Java server (languagetool.org) as a backend for a Python grammar checker. I updated it to use the latest versions of Java and the LanguageTool API, added a few features, and voila! There is now a free, easy-to-use Python grammar-checking library :)