# 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/1.9.3/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. The field max_event_history will only give you these last events, it can be set in the tracker_store ### `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`](https://legacy-docs-v1.rasa.com/1.9.3/api/tracker/#rasa.core.trackers.DialogueStateTracker) ### `current_slot_values()` Return the currently set values of the slots. Return type: `Dict`[`str`, `Any`] ### `current_state`( _event_verbosity=_) 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`](https://legacy-docs-v1.rasa.com/1.9.3/api/tracker/#rasa.core.trackers.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`](https://legacy-docs-v1.rasa.com/1.9.3/api/tracker/#rasa.core.trackers.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. Parameters: - **event_type** – The type of event you want to find. - **action_names_to_exclude** – Events of type ActionExecuted which should be excluded from the results. Can be used to skip action_listen events. - **skip** – Skips n possible results before return an event. 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. Returns: Entity values. 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. Return type: `int` ### `init_copy()` Creates a new state tracker with the same initial values. Return type: [`DialogueStateTracker`](https://legacy-docs-v1.rasa.com/1.9.3/api/tracker/#rasa.core.trackers.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. Returns: True if last executed action had name name, otherwise False. 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 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. Return type: [`DialogueStateTracker`](https://legacy-docs-v1.rasa.com/1.9.3/api/tracker/#rasa.core.trackers.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` *I can help you get started with Rasa and answer your technical questions.*