###
14.3.2.1 Understanding option actions

Actions tell `optparse` what to do when it encounters an option on the command line. There is a fixed set of actions hard-coded into `optparse`; adding new actions is an advanced topic covered in section 14.3.5, Extending `optparse`. Most actions tell `optparse` to store a value in some variable--for example, take a string from the command line and store it in an attribute of `options`.

If you don't specify an option action, `optparse` defaults to `store`.