# 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 behaviour, check out the docs on [Session configuration](https://legacy-docs-v1.rasa.com/1.9.1/core/domains/#session-config). ## Class `rasa.core.trackers.DialogueStateTracker` Maintains the state of a conversation. ### Attributes - **max_event_history**: The field max_event_history will only give you these last events; it can be set in the tracker_store. ### 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 serialized 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()` Returns the currently set values of the slots. Return type: `Dict[str, Any]` - `current_state(event_verbosity=)` Returns the current tracker state as an object. Return type: `Dict[str, Any]` - `events_after_latest_restart()` Returns 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 is representing 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. Returns: event which matched the query or None if no event matched. 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 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 serialized Dialogue to update the trackers state. 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. 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`