I have read vegaseat's "Projects for the Beginner" sticky and got really interrested in the eqaution solver for physics or mathematics problem. I just need a little Python hint how to get this started.

In C I used lots of switch/case statements. Now Python does not have a switch/case construct. You could use mutliple if/elif, or better a dictionary with lambda functions. Come to think of it, a Python dictionary almost looks like a C switch/case. Read up on lambda too.