Refer, please : https://docs.python.org/2/howto/argparse.html Search for the first instance of : args.square When you want to show that : Square of 5 is 25, calling the number '5' args.square is very counterintuitive. If you call it args.base_number, it does not at once tell whether the square or cube or root of the base is being calcaulated. Calling it args.num_to_be_squared is too long. But calling it args.square is so confusing. print args.num**2 ## print the square of the number reads better, and is not confusing. - dn