Make sure you have Node 18 selected in your Project Settings to use python@3.9. If you have it deployed on Node 20 or later, it will not work as Python 3.9 uses legacy build image: Using the Python Runtime with Vercel Functions
python 3.9 is indeed too old, as i use 3.12. But v0 told me to use 3.9 instead of 3.12 although vercel docs say the opposite. However, this has nothing to do with node or something like that. It is pure python.
Even though you aren’t using Node in your application, the Node version matters to deploy in our build system. This means you need to make sure Node version is set to Node 20+ in order to use Python 3.12
If you are using Python 3.9, you need to make sure Node version is set to 18.x in your project.