Check out https://www.pantsbuild.org/python_readme.html#configure-the-python-version for how you can mark what interpreter versions your targets and overall project is compatible with. https://www.pantsbuild.org/python_readme.html#configure-the-python-version You can have some targets that are Python 2 only, some that are Python 3 only, etc, and Pants will understand it all 🙂 Pants will error with a helpful message if it can’t find a compatible interpreter because the constraints conflict, e.g. when you try to use a Python-2 only target with a Python-3 target.