The following is an (incomplete) list of Open Source projects which I have started or contributed to, with various degrees of involvement. See my Github page for a more complete list of my projects.

PyPy

I have been a core contributor to various aspects of PyPy since 2006, including the development of the CLI/.NET and JVM backends, the CLI JIT backend, the PyPy JIT compiler generator, the PyPy Python interpreter and the testing infrastructure.
Currently, my main interest is to improve the performance of C extensions, and in particular of the scientific stack: in the recent years I worked on improving cpyext and started HPy.
In the past, I leaded the migration of the PyPy repository from Subversion to Mercurial, and for a short period of time I was the project lead of the py3k subproject, whose goal is to have a PyPy interpreter compatible with Python 3.

HPy

In 2019, I founded and started the HPy project together with other PyPy, CPython and Cython developers. HPy is an ambitious project, whose final goal is to greatly improve the quality of the Python ecosystem. Among the other things,, it will help to greatly improve the performance of C/scientific extensions on PyPy. See also the talk which I gave to the Python Language Summit 2020 and the corresponding slides.

pdb++

pdb++ is a project which I started and currently maintain. It is an extension of the pdb Python debugger which is found in the standard library. It comes with lots of fancy features, including: colorful TAB completion of Python expressions, optional syntax highlighting of code listings, sticky mode (see picture), several new commands to be used from the interactive (Pdb++) prompt.

fancycompleter

fancycompleter is a project which I started and currently maintain. It is a module to improve your experience in Python by adding TAB completion to the interactive prompt. It is an extension of the standard library's rlcompleter module. Its best feature is that the completions are displayed in different colors, depending on their type.

pytest

pytest is one of the best test tools for Python. I have used it extensively both with PyPy and in my own projects, and I have contributed some patches and features to it. Moreover, I wrote some plugins and extensions, such as pytest-initargs and pytest-emacs.

vcsdeploy

vcsdeploy is a project which I started and currently maintain. vcsdeploy allows you to easily deploy updates of your application to your customers through your favorite Version Control System (e.g. Mercurial).

Camelot

Camelot is an open source RAD framework that leverages Python, Sqlalchemy and Qt to build rich desktop applications. I have contributed various patches and features to Camelot. Moreover, I have developed xmlot, an extension which makes it possible to build Camelot-based applications to edit XML files.