Rasa Fallback tutorial

actions.py

from rasa_sdk import Tracker, Action
from typing import Any, Text
from rasa_sdk.executor import CollectingDispatcher
from rasa_sdk.types import DomainDict


# DO NOT copy paste whole file

class ActionFallback(Action):
    def name(self) -> Text:
        return "action_fallback"

    def run(
            self,
            dispatcher: "CollectingDispatcher",
            tracker: Tracker,
            domain: "DomainDict",
    ) -> List[Dict[Text, Any]]:
        # add different functionalities like google search, wiki search, etc to provide more answer
        latest_message = tracker.latest_message.get("text")
        dispatcher.utter_message(text="sorry, can you please repharse your question and try again?")
        return []

config.yml

# This config.yml is based on 2.x you can still use below values of FallbackClassifier and RulePolicy in 3.x 
# DO NOT copy paste this whole file
language: en

pipeline:
  - name: WhitespaceTokenizer
  - name: LexicalSyntacticFeaturizer
  - name: CountVectorsFeaturizer
  - name: CountVectorsFeaturizer
    analyzer: char_wb
    min_ngram: 1
    max_ngram: 4
  - name: DIETClassifier
    epochs: 100
    constrain_similarities: true
  - name: FallbackClassifier
    threshold: 0.3 # make sure to test the confidences of your intents and then specify this value
    fallback_action: "action_fallback" # automatically gets triggered when fallback occurs

policies:
  - name: MemoizationPolicy
  - name: RulePolicy # added alternative to above fallback classifier, you can use any one or both.
    core_fallback_threshold: 0.3 # make sure to test the confidences of your stories, rules and domain and then specify this value
    core_fallback_action_name: action_fallback
    enable_fallback_prediction: true
  - name: TEDPolicy
    max_history: 5
    epochs: 100
    constrain_similarities: true

rules.yml

version: "2.0" # make sure to change as per your rasa version
  - rule: fallback
    steps:
      - intent: nlu_fallback
      - action: action_fallback

domain.yml also needs to be updated with the following lines.

actions:

• action_fallback