Basic calculator program in Python
This being Python, where indentation is significant, it is important to consistently follow the convention of four spaces per level.

You shouldn't format the square root as %d, since the result is rarely an integer.

There are several recommendations that I could make about organizing this code, but the single most important point is that functions should not be treated as goto labels.  If you need a loop, then write a loop using while or for.  Don't have main call main().  Don't have repeat call main().  Don't have repeat call repeat().  Otherwise, you end up with spaghetti code.