# 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/1.10.12/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/1.10.12/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`

### `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/1.10.12/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]`

### `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 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.

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`](https://legacy-docs-v1.rasa.com/1.10.12/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.

**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/1.10.12/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`

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