# Rasa SDK

Rasa SDK provides the tools you need to write custom actions in python.

## [Installation](https://legacy-docs-v1.rasa.com/1.10.11/api/rasa-sdk/#installation)
Use `pip` to install `rasa-sdk` on your action server.
```
pip install rasa-sdk
```
Note
You do not need to install `rasa` for your action server. E.g. if you are running Rasa in a docker container, it is recommended to create a separate container for your action server. In this separate container, you only need to install `rasa-sdk`.

## [Running the Action Server](https://legacy-docs-v1.rasa.com/1.10.11/api/rasa-sdk/#running-the-action-server)
If you have `rasa` installed, run this command to start your action server:
```
rasa run actions
```
Otherwise, if you do not have `rasa` installed, run this command:
```
python -m rasa_sdk --actions actions
```
You can verify that the action server is up and running with the command:
```
curl http://localhost:5055/health
```
You can get the list of registered custom actions with the command:
```
curl http://localhost:5055/actions
```
The file that contains your custom actions should be called `actions.py`. Alternatively, you can use a package directory called `actions` or else manually specify an actions module or package with the `--actions` flag.

## [Actions](https://legacy-docs-v1.rasa.com/1.10.11/api/rasa-sdk/#actions)
The `Action` class is the base class for any custom action. It has two methods that both need to be overwritten, `name()` and `run()`.

In a restaurant bot, if the user says “show me a Mexican restaurant”, your bot could execute the action `ActionCheckRestaurants`, which might look like this:
```python
from rasa_sdk import Action
from rasa_sdk.events import SlotSet

class ActionCheckRestaurants(Action):
   def name(self) -> Text:
      return "action_check_restaurants"

def run(self,
           dispatcher: CollectingDispatcher,
           tracker: Tracker,
           domain: Dict[Text, Any]) -> List[Dict[Text, Any]]:

cuisine = tracker.get_slot('cuisine')
      q = "select * from restaurants where cuisine='{0}' limit 1".format(cuisine)
      result = db.query(q)

return [SlotSet("matches", result if result is not None else [])]
```
You should add the action name `action_check_restaurants` to the actions in your domain file. The action’s `run()` method receives three arguments. You can access the values of slots and the latest message sent by the user using the `tracker` object, and you can send messages back to the user with the `dispatcher` object, by calling `dispatcher.utter_message`.

### [Customizing the session start action](https://legacy-docs-v1.rasa.com/1.10.11/api/rasa-sdk/#customizing-the-session-start-action)
The default behavior of the session start action is to take all existing slots and to carry them over into the next session. Let’s say you do not want to carry over all slots, but only a user’s name and their phone number. To do that, you’d override the `action_session_start` with a custom action that might look like this:
```python
from typing import Text, List, Dict, Any
from rasa_sdk import Action, Tracker
from rasa_sdk.events import SlotSet, SessionStarted, ActionExecuted, EventType
from rasa_sdk.executor import CollectingDispatcher

class ActionSessionStart(Action):
    def name(self) -> Text:
        return "action_session_start"

@staticmethod
    def fetch_slots(tracker: Tracker) -> List[EventType]:
        slots = []
        for key in ("name", "phone_number"):
            value = tracker.get_slot(key)
            if value is not None:
                slots.append(SlotSet(key=key, value=value))
        return slots

async def run(
        self,
        dispatcher: CollectingDispatcher,
        tracker: Tracker,
        domain: Dict[Text, Any],
    ) -> List[EventType]:
        events = [SessionStarted()]
        events.extend(self.fetch_slots(tracker))
        events.append(ActionExecuted("action_listen"))
        return events
```
Note
You need to explicitly add `action_session_start` to your domain to override this custom action.

## [Events](https://legacy-docs-v1.rasa.com/1.10.11/api/rasa-sdk/#events)
An action’s `run()` method returns a list of events. For more information on the different types of events, see [Events](https://legacy-docs-v1.rasa.com/1.10.11/api/events/#events). There is an example of a `SlotSet` event above.

## [Tracker](https://legacy-docs-v1.rasa.com/1.10.11/api/rasa-sdk/#tracker)
The `rasa_sdk.Tracker` lets you access the bot’s memory in your custom actions. You can get information about past events and the current state of the conversation through `Tracker` attributes and methods.