Writing a text editor is way harder than it looks so I wouldn't start with that.

(On the other hand, if people knew how hard it was to make a particular program before they started, we wouldn't have most of the software we have today.)

Exactly. Laugh in the face of people who "know", and aim for the sky.

Write a new O/S. Write new firmware for something... The world is our oyster.

I only mention it because it's one of the apps I first wrote when learning.

You get to understand about UI, data structures etc etc Even if you end up only implementing some pop down menus, it's still worth doing. By that time you may have decided to do something else anyway...

The key is choose anything and start building it.

Cloning Tetris is a good start: It's easy and you know when you are finished. PyGame works well for that.

I'd advise against using any framework. Maybe use it to start with, realize why it completely sucks, and write your own.

PyGame is a binding to SDL. "Simple DirectMedia Layer is a cross-platform multimedia library designed to provide low level access to audio, keyboard, mouse, joystick, 3D hardware via OpenGL, and 2D video framebuffer."

May I suggest that going to the bare metal (yes, programming languages are a kind of framework, too) for implementing Tetris is a bit over the top?

Maybe :) but most of the fun is straying from the often walked tracks.

Which basically amounts to "Don't write a twitter client" right now.