I’m a python dev, not really sure what’s most in-demand right now.

Strictly Android? I like SoloLearn. Pretty stream-lined. I’ve done a bunch of exercises on it to kill time.

Depending on your patience, exercism.org and termux or an in-browser ide.

Edit: I do agree with all the replies saying you can’t code on your phone to an extent.

It’s definitely not the best way to start but you can make it work for you if you use Termux to run your scripts.

Nano, the terminal editor is alright. Micro let’s you use the touch screen. There’s also Acode which is a straight-up android app that you can code in.

To be clear, learning to code on your phone is going to be way tougher than on a computer. There’s just more hurdles but it’s not impossible. I do a little coding on my phone here and there, mostly for little scripts or small bugfixes. If I’m coding big stuff on my phone, I use something like repl.it

I don’t know your situation but if a phone is all you got, then you can do it, just expect to be doing a lot more googling than if you were on a computer.