Modern Python Standard Library Cookbook

How it works...

We used the ArgumentParser.add_argument method to populate the list of available options. For every argument, it's possible to also provide a help option, which will declare the help string for that argument.

Positional arguments are provided with just the name of the argument:

parser.add_argument("number", 
                    help="One or more numbers to perform an operation on.",
                    nargs='+', type=int)

The nargs option tells ArgumentParser how many times we expect that argument to be specified, the + value means at least once or more than once. Then type=int tells us that the arguments should be converted to integers.

Once we have the numbers to which we want to apply the operation, we need to know the operation itself:

parser.add_argument('-o', ...