6.21.4 Option Callbacks
When optparse's built-in actions and types aren't quite enough for your needs, you have two choices: extend optparse or define a callback option. Extending optparse is more general, but overkill for a lot of simple cases. Quite often a simple callback is all you need.
There are two steps to defining a callback option:
-
define the option itself using the
callback
action -
write the callback; this is a function (or method) that
takes at least four arguments, as described below
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