Warning: This document is for an old version of Rasa Core.

Custom Actions

There are two kinds of actions in Rasa Core. The simplest are UtterActions, which just send a message to the user. You define them by adding an entry to the action list in your rasa_core.domain.Domain. There also needs to be a matching utterance. For example, if there’s an action utter_greet then there should also be an utterance template called utter_greet in your domain.

What about more complicated actions? In general, an action can run any code you like. Custom actions can turn on the lights, add an event to a calendar, check a user’s bank balance, or anything else you can imagine.

Custom Actions Written in Python

In a restaurant bot, if the user says “show me a Mexican restaurant”, your bot could execute the action ActionCheckRestaurants, which might look like this:

from rasa_core.actions import Action
from rasa_core.events import SlotSet

class ActionCheckRestaurants(Action):
   def name(self):
      # type: () -> Text
      return "action_check_restaurants"

   def run(self, dispatcher, tracker, domain):
      # type: (Dispatcher, DialogueStateTracker, Domain) -> List[Event]

      cuisine = tracker.get_slot('cuisine')
      q = "select * from restaurants where cuisine='{0}' limit 1".format(cuisine)
      result = db.query(q)

      return [SlotSet("matches", result if result is not None else [])]

The action’s run method receives three arguments. You can access the values of slots and the latest message sent by the user using the tracker object, and you can send messages back to the user with the dispatcher object, by calling dispatcher.utter_template, dispatcher.utter_message, or any other Dispatcher method.

Details of the run method:

Action.run(dispatcher: Dispatcher, tracker: DialogueStateTracker, domain: Domain) → List[Event]

Execute the side effects of this action.

Parameters:

• dispatcher (Dispatcher) – the dispatcher which is used to send messages back to the user. Use dispatcher.utter_message() or any other rasa_core.dispatcher.Dispatcher method.
• tracker (DialogueStateTracker) – the state tracker for the current user. You can access slot values using tracker.get_slot(slot_name) and the most recent user message is tracker.latest_message.text.
• domain (Domain) – the bot’s domain

Returns:

A list of rasa_core.events.Event instances

Return type:

List[Event]