Here's the list of Python packages we have been using / have discovered in June 2018:

Python Fire — turn (almost) any Python object into a CLI tool.
Hug — it will probably be another year or two before we can switch our Flask-based projects to Hug, but it is so close... Hug's main selling point (for us) is the ease of re-targeting (web, local, cli) with decorators. Hug has the potential to disrupt the Python REST framework scene.
Pipenv — makes working with virtual envs and pip much, much more easier than before AND makes package audits so much easier. You will forget that pip and virtualenv exist.