If you are a 3d printing enthusiast then you probably know about or use Octoprint the phenomenal piece of open-source software developed and maintained by Gina Häußge. Octoprint is built on python and is compatible with python version 2 and 3. Gina and others have worked hard to prepare for python 2 EOL. Currently a large majority of users are using python 2. Python 3 support is ready and the majority of plugins are python 3 compatible so now is a good time to upgrade.
To help you with the process, Charlie Powell has created a script that will automate the process. See the blog post here. I’ve been on the python 3 version for awhile and have no issues.