argument parser: to execute single function, and subsequent functions also

[dalwood]

I'm going to suggest a slightly different approach. How about if you allowed options such as -f 1 2 3? Meaning, run function_1(), then function_2(), followed by function_3().

This can be done with a single add_argument like this:

parser.add_argument("-f", nargs='+', default=[])

nargs='+' means any number of args, but at least 1. You can also use nargs='*' to mean any number, including 0. Including default=[] is nice because then your code doesn't have keep testing first if cmd_arguments.f == None.

The namespace object returned by parse_args() (cmd_arguments in your example) will have a member named f of type list. Now you can use if statements like:

if 1 in cmd_arguments.f:
    function_1()

This approach also gives great flexibility on not only which functions are to be run, but even what order: -f 3 1 2.