ABAP_starter VS PyRFC

Specifically for ABAP, there is just one free SAP course for beginners. It is a decent course but it does not really teach classic ABAP that you're probably encountering if you're working with an on-premise system. For classic ABAP, to be honest, there is no better source than my own book. :) It was written for complete beginners, explains very basic IF... THEN... stuff. I've heard from many functional consultants who used it to learn ABAP and so far no unhappy customers. The book is also recommended by ABAP Starter.

Couple of resources to start with. This article describes different roles of SAP professionals. ABAP Starter is a great resource for anyone thinking about learning ABAP. Most of SAP development still revolves around ABAP. There are other specializations these days but there is already competition from trained developers and learning curve might be too challenging.

ABAP Starter is a good starting point.

This is a good resource for beginners too: https://github.com/Keller-Michael/ABAP_starter

ABAP Starter (not just for "starters" and has more links)

Read ABAP Starter.

There are several libraries that implement SAP RFC that you could use e.g. https://sap.github.io/PyRFC/, depending on the language you want to use. Other possibilities are wrapping the RFC in a web service to be able to call it via SOAP or wrap it in a OData Service and call this. Just one remark: Using this opens the door to the whole indirect use discussed. That means that depending on your use case SAP may want additional money for each call. Google SAP digital access if you are interested in learning more.

PyRFC

If you like to automatic something with python you should consider calling the appropriate functions directly (without going to the cmd line) via PyRFC.