MODDERS BEWARE: The Sims 4 is getting a Python Upgrade

SimGuruModSquad has published a forum post on The Sims Official Forums saying that The Sims 4’s upcoming update is going to change and upgrade the current version of Python – a programming language and software which is used to help develop the game itself.

The upgrade will change the .pyo extension which is going to be replaced by .pyc. This change is going to affect ALL script mods meaning that since November they’ll completely stop functioning.

SimGuruModSquad wanted to make sure that all modders are ready and aware of this change so they can prepare and upgrade their script mods in time.

Hi everyone,

I want to give you a heads up that in an upcoming release, we will be upgrading the version of Python used by the game. We currently use Python 3.3.5 and will be moving to Python 3.7.0. Once this change is released, all compiled script mods will completely stop working. Note that in this new version of Python, the .pyo extension is replaced by .pyc, see

We know this will have impact on your script mod authoring pipelines so wanted to provide notice in advance so you can be ready for the change when it arrives. To assist, I’ve attached the Python scripts from the currently released version of the game (v1.46.18) recompiled under Python 3.7.0.

If all goes as planned, this change should arrive in November.

Note that there will not be any fundamental changes to tuning data, other than the typical types of changes we make to tuning for patches.



Written by Jovan Jovic

Founder of the Sims Community website. I do plenty of things around here including writing articles such as "Top 10 Disney Princesses in The Sims", social media management, video content creation, streaming and more!


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  1. it’s nice that they’re giving modders a heads up! are script mods the mods that change the way the game works, instead of new clothes and makeup and stuff?

    • Script mods are mostly used to add custom interactions, so functional objects that contain custom functionality are also affected. Note that only adding new interactions requires scripting, modifying vanilla interactions only requires tuning, many game mods are done entirely by xml tuning.

      • So the ones that are just a .PACKAGE file are fine, it’s just the ones that have a .TS4SCRIPT after them that are affected? That’s easy enough. Thanks for the help!

        • Absolutely not!
          The mods that change the game will stopworking (I can give you some exemples … Like Go To School by Zerbu or Road to Fame by Sacrificial) Basically every mods changing how the game works even the .package ones

          But the custom content (clothes, hair …) will stay unchanged 🙂

      • Thanks so much for the verification, I heard on tumblr to delete all your cas cc and I was freaking out. I don’t use many game play mods so I should be good!

  2. This’ll break MC Command Center, which is the most essential scripting mod and without it, Sims 4 is basically unplayable trash.

    Obviously best thing you can do is wait and don’t update Sims 4 until MC Command Center and any other scripted mod you need is updated to work with the new python update.

    The MC Command Center is very actively developed so it’ll eventually get working, depending on the complexity of converting to the new format. The biggest problem is really old mods that are basically abandoned, those will be completely useless after this.

    Hopefully this will improve performance… so tired of seeing huge delays between commands…

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