Just started learning Python yesterday. I have previous student experience in FORTRAN, and Java. The app is called SoloLearn and it has more than one programming self tutor on it.
Don't have to download anything else special, such as a compiler since it executes line by line by the interpretor.
You want the language that is cross-platform. Check out SoloLearn, each lesson had comments already written by previous students so don't get stuck if need help.
Check out this chart here to choose:
According to above chart, Python is the easiest to learn.