First-time coder at 34, trying to build an API in Python. Can it be done in 3 months?

Yes, you definitely can.

A resource that I give everyone is Build APIs You Won't Hate, which is a programming-language agnostic approach to building professional APIs.

I am unsure about your current ability but I would ensure that you are competent with general programming concepts such as variables, loops, classes, functions, etc. before reading.

Best of luck!

Nice wishing you the best of luck! I think you can totally do it. It'll be challenging but if you have the time and determination you can do it. It would probably benefit you to find a mentor online to talk with or an accountability buddy.

It can absolutely be done.

I don't know whether you've decided what library/framework to build your API with, or how complicated it needs to be (e.g. are authentication and authorization needed?). But Flask is a simple, lightweight library to start with:
https://www.youtube.com/results?search_query=flask+api

For more heavyweight stuff, I'd look at Django Rest Framework. But to get a feel for the flow, I'd start with a simple Flask API first.

Of course you can build it, 3 months is more than enough time.
PyCharm is awesome tool, and it comes with built-in pyhton virtual environments. So for every python project you can have specific venv and they won't affect your host system.

Oh definitely! Maybe not something complex, but you'll for sure be able to build an API or something in 3 months. Just keep learning :)

Build and deploy an API in low-code using Linx
https://linx.software/build-and-deploy-api/

I learned php/mysql and jquery/bootstrap (but didnt learn any real javascript unfortunately) in ~2017 via youtube and stackoverflow. Within 3 months I made an entire SaaS web application for project management that currently around 30 companies use. Its definitely possible, if it is something you are focusing on full time. Once you get into part time, it really depends on what level of 'finished' you are looking for.

You can get something working in 2 days, but finishing it to a level you are happy with can take another 20 days on top of that. I once made an entire feature I was pretty proud of during an allnighter. And then took 2 weeks to make it nice. And that was once I already had a decent amount of experience.

One piece of advice that I think can actually help you.. as a TOTAL beginner, entire youtube tutorials of how to make something similar to what you want are very helpful. Sometimes I would spin my wheels blindly searching Stackoverflow without knowing exactly what I was doing.. only to the search youtube for a tutorial on that thing and get not only the exact answer I wanted but 20 minutes of discussion and explanation about it. Stackoverflow is very helpful for syntax and basic logic issues in basic code, but youtube tutorials are better for learning a slightly bigger concept.

Maybe something like this.. but warning.. I didnt even spend 20 seconds checking if this is any good.
https://www.youtube.com/watch?v=qbLc5a9jdXo