# 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/1.10.8/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/1.10.8/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=<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`

### `classmethod 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/1.10.8/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, None, None]`

### Additional methods  
- `get_last_event_for(event_type, action_names_to_exclude=None, skip=0)`  
- `get_latest_entity_values(entity_type, entity_role=None, entity_group=None)`  
- `get_latest_input_channel()`  
- `get_slot(key)`  
- `idx_after_latest_restart()`  
- `init_copy()`  
- `is_paused()`  
- `last_executed_action_has(name, skip=0)`  
- `past_states(domain)`  
- `recreate_from_dialogue(dialogue)`  
- `reject_action(action_name)`  
- `replay_events()`  
- `set_form_validation(validate)`  
- `set_latest_action_name(action_name)`  
- `travel_back_in_time(target_time)`  
- `trigger_followup_action(action)`  
- `update(event, domain=None)`