These docs are for version 1.x of Rasa Open Source.

# Tracker

Trackers maintain the state of a dialogue between the assistant and the user in the form of conversation sessions. To learn more about how to configure the session behavior, check out the docs on [Session configuration](https://legacy-docs-v1.rasa.com/1.10.24/core/domains/#session-config).

## class rasa.core.trackers.DialogueStateTracker(sender_id, slots, max_event_history=None, sender_source=None)
Maintains the state of a conversation.

### Methods

- **applied_events()**  
  Returns all actions that should be applied - w/o reverted events.
  
  **Return type**: `List[Event]`

- **as_dialogue()**  
  Return a `Dialogue` object containing all of the turns. This can be serialised and later used to recover the state of this tracker exactly.

**Return type**: `Dialogue`

- **change_form_to(form_name)**  
  Activate or deactivate a form.

**Return type**: `None`

- **clear_followup_action()**  
  Clears follow up action when it was executed.

**Return type**: `None`

- **copy()**  
  Creates a duplicate of this tracker.

**Return type**: `DialogueStateTracker`

- **current_slot_values()**  
  Return the currently set values of the slots.

**Return type**: `Dict[str, Any]`

- **current_state(event_verbosity=<EventVerbosity.NONE: 1>)**  
  Return the current tracker state as an object.

**Return type**: `Dict[str, Any]`

- **events_after_latest_restart()**  
  Return a list of events after the most recent restart.

**Return type**: `List[Event]`

- **export_stories(e2e=False, include_source=False)**  
  Dump the tracker as a story in the Rasa Core story format. Returns the dumped tracker as a string.

**Return type**: `str`

- **export_stories_to_file(export_path='debug.md')**  
  Dump the tracker as a story to a file.

**Return type**: `None`

- **from_dict(sender_id, events_as_dict, slots=None, max_event_history=None)**  
  Create a tracker from dump. The dump should be an array of dumped events. When restoring the tracker, these events will be replayed to recreate the state.

**Return type**: `DialogueStateTracker`

- **generate_all_prior_trackers()**  
  Returns a generator of the previous trackers of this tracker. The resulting array represents the trackers before each action.

**Return type**: `Generator[DialogueStateTracker, None, None]`

- **get_last_event_for(event_type, action_names_to_exclude=None, skip=0)**  
  Gets the last event of a given type which was actually applied.

**Return type**: `Optional[Event]`

- **get_latest_entity_values(entity_type, entity_role=None, entity_group=None)**  
  Get entity values found for the passed entity type and optional role and group in the latest message.

**Return type**: `Iterator[str]`

- **get_latest_input_channel()**  
  Get the name of the input_channel of the latest UserUttered event.

**Return type**: `Optional[str]`

- **get_slot(key)**  
  Retrieves the value of a slot.

**Return type**: `Optional[Any]`

- **idx_after_latest_restart()**  
  Return the idx of the most recent restart in the list of events. If the conversation has not been restarted, `0` is returned.

**Return type**: `int`

- **init_copy()**  
  Creates a new state tracker with the same initial values.

**Return type**: `DialogueStateTracker`

- **is_paused()**  
  State whether the tracker is currently paused.

**Return type**: `bool`

- **last_executed_action_has(name, skip=0)**  
  Returns whether last ActionExecuted event had a specific name.

**Return type**: `bool`

- **past_states(domain)**  
  Generate the past states of this tracker based on the history.

**Return type**: `deque`

- **recreate_from_dialogue(dialogue)**  
  Use a serialised Dialogue to update the tracker’s state. This uses the state as is persisted in a `TrackerStore`. If the tracker is blank before calling this method, the final state will be identical to the tracker from which the dialogue was created.
  
  **Return type**: `None`

- **reject_action(action_name)**  
  Notify active form that it was rejected.

**Return type**: `None`

- **replay_events()**  
  Update the tracker based on a list of events.

**Return type**: `None`

- **set_form_validation(validate)**  
  Toggle form validation.

**Return type**: `None`

- **set_latest_action_name(action_name)**  
  Set latest action name and reset form validation and rejection parameters.

**Return type**: `None`

- **travel_back_in_time(target_time)**  
  Creates a new tracker with a state at a specific timestamp. A new tracker will be created and all events previous to the passed time stamp will be replayed. Events that occur exactly at the target time will be included.

**Return type**: `DialogueStateTracker`

- **trigger_followup_action(action)**  
  Triggers another action following the execution of the current.

**Return type**: `None`

- **update(event, domain=None)**  
  Modify the state of the tracker according to an `Event`.

**Return type**: `None`

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