If you make or use mods in your game which significantly expand on default behaviour (“script mods”) then this news is for you.
In an upcoming release, likely to be this November, The Sims 4 will update the version of Python it uses from 3.3.5 to 3.7.0. This will mean that older mods may stop working. There are a few major changes between these two releases which may break older code. For example, PEP 488 which was introduced in version 3.5 essentially replaced .pyo files with .pyc files. You can download all the game scripts for the current version of the game recompiled for Python 3.7.0 on The Sims 4 forum at the link below.
Modders who want to get ahead of this change and update their content can find more information here: https://forums.thesims.com/en_uS/discussion/949019/python-upgrade-coming-soon