In http://docs.python.org/dev/library/argparse.html#action, when describing an arbitrary action, the documentation states, "You can also specify an arbitrary action by passing an object that implements the Action API." This statement does not link to any documentation on the Action API and does not describe the API except to give an example.

Furthermore, the example contradicts the description. The description says "pass an object" but the example passes a class.

The documentation should clarify the text relating to the example and should document the expected interface for a custom action.