How to programmatically exit without Traceback?

[nilamo]

Should I be able to run from the command line?

When I ran the file.py I initially got the print lines as output. I then entered sum_two(3.5,7) and got:
Output:'sum_two' is not recognized as an internal or external command,operable program or batch file.

You should be able to run the program from the command line, but not components within that program.