As per the title.

I'm thinking of learning to code and one of the things I'd like to use the knowledge for would be designing my own poker software/apps. Does anyone experienced in these matters know which programming language would be best for this purpose?

I've got courses in my locality on Java and Python, so one of those two would be preferable.

Probably C++

Out of those two I'd prob pick Python

It actually depends on your personality. I don't learn things step by step, I learn kind of by doing. So the thing that taught me how to code was forcing api keys to work ( so i could make a cool thing on a web page) in javascript/html/css despite not knowing html/css or javascript at all. How I didn't learn to code was step by step solving python algoritms and basic programs. I think html/css and javascript stuff if you're more creative and "right brained" and python if you're more "left brained" . Javascript/ python pretty much get you everything unless you're a hardcore hacker or a hardcore genius, then you might consider c or c++ but for most people that is counterproductive.