Why do you want to do this? If you're looking to trace the program flow, check out the built-in debugger. You can step through your program, set breakpoints on lines, subroutines, and conditionals. You can also print stack backtraces and print complex data structures on the fly to verify that they're correct.

I suspect that a lot of people overlook the usefulness of the debugger as many questions that are answered here would quickly be resolved with a quick debugger session.

Check it out. It will quickly become your best friend. And yes, if you step through your program, it will automatically say what line the program is on at all times :) In fact, everything that you describe in your title is contained in the debugger.

Cheers,
Ovid

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