# Slots

## What are slots?
**Slots are your bot’s memory.** They act as a key-value store which can be used to store information the user provided (e.g their home city) as well as information gathered about the outside world (e.g. the result of a database query).

Most of the time, you want slots to influence how the dialogue progresses. There are different slot types for different behaviors.

For example, if your user has provided their home city, you might have a `text` slot called `home_city`. If the user asks for the weather, and you _don’t_ know their home city, you will have to ask them for it. A `text` slot only tells Rasa Core whether the slot has a value. The specific value of a `text` slot (e.g. Bangalore or New York) doesn’t make any difference.

If the value itself is important, use a `categorical` or a `bool` slot. There are also `float`, and `list` slots. If you just want to store some data, but don’t want it to affect the flow of the conversation, use an `unfeaturized` slot.

## How Rasa Uses Slots
The `Policy` doesn’t have access to the value of your slots. It receives a featurized representation. The policy just sees a `1` or `0` depending on whether it is set.

**You should choose your slot types carefully!**

## How Slots Get Set
You can provide an initial value for a slot in your domain file:
```yaml
slots:
  name:
    type: text
    initial_value: "human"
```
You can get the value of a slot using `.get_slot()` inside `actions.py` for example:
```python
data = tracker.get_slot("slot-name")
```

### Slots Set from NLU
If your NLU model picks up an entity, and your domain contains a slot with the same name, the slot will be set automatically. For example:
```yaml
# story_01
* greet{"name": "Ali"}
  - slot{"name": "Ali"}
  - utter_greet
```
In this case, you don’t have to include the `- slot{}` part in the story, because it is automatically picked up.

To disable this behavior for a particular slot, you can set the `auto_fill` attribute to `False` in the domain file:
```yaml
slots:
  name:
    type: text
    auto_fill: False
```

### Slots Set By Clicking Buttons
You can use buttons as a shortcut. Rasa Core will send messages starting with a `/` to the `RegexInterpreter`, which expects NLU input in the same format as in story files, e.g. `/intent{entities}`. For example, if you let users choose a color by clicking a button, the button payloads might be `/choose{"color": "blue"}` and `/choose{"color": "red"}`.
You can specify this in your domain file:
```yaml
utter_ask_color:
- text: "what color would you like?"
  buttons:
  - title: "blue"
    payload: '/choose{"color": "blue"}'
  - title: "red"
    payload: '/choose{"color": "red"}'
```

### Slots Set by Actions
The second option is to set slots by returning events in custom actions. In this case, your stories need to include the slots. For example:
```yaml
slots:
   account_type:
      type: categorical
      values:
      - premium
      - basic
```

```python
from rasa_sdk.actions import Action
from rasa_sdk.events import SlotSet
import requests

class FetchProfileAction(Action):
    def name(self):
        return "fetch_profile"

def run(self, dispatcher, tracker, domain):
        url = "http://myprofileurl.com"
        data = requests.get(url).json()
        return [SlotSet("account_type", data["account_type"])]
```

```yaml
# story_01
* greet
  - action_fetch_profile
  - slot{"account_type" : "premium"}
  - utter_welcome_premium

# story_02
* greet
  - action_fetch_profile
  - slot{"account_type" : "basic"}
  - utter_welcome_basic
```

## Slot Types
### Text Slot
`text`
**Use For**: User preferences where you only care whether or not they’ve been specified.
**Example**:
```yaml
slots:
   cuisine:
      type: text
```
**Description**: Results in the feature of the slot being set to `1` if any value is set. Otherwise, the feature will be set to `0` (no value is set).

### Boolean Slot
`bool`
**Use For**: True or False
**Example**:
```yaml
slots:
   is_authenticated:
      type: bool
```
**Description**: Checks if slot is set and if True.

### Categorical Slot
`categorical`
**Use For**: Slots which can take one of N values.
**Example**:
```yaml
slots:
   risk_level:
      type: categorical
      values:
      - low
      - medium
      - high
```
**Description**: Creates a one-hot encoding describing which of the `values` matched.

### Float Slot
`float`
**Use For**: Continuous values
**Example**:
```yaml
slots:
   temperature:
      type: float
      min_value: -100.0
      max_value:  100.0
```

### List Slot
`list`
**Use For**: Lists of values
**Example**:
```yaml
slots:
   shopping_items:
      type: list
```

### Unfeaturized Slot
`unfeaturized`
**Use For**: Data you want to store which shouldn’t influence the dialogue flow.
**Example**:
```yaml
slots:
   internal_user_id:
      type: unfeaturized
```

## Custom Slot Types
Maybe your restaurant booking system can only handle bookings for up to 6 people. In this case, you want the value of the slot to influence the next selected action. You can do this by defining a custom slot class.

```python
from rasa.core.slots import Slot

class NumberOfPeopleSlot(Slot):
    def feature_dimensionality(self):
        return 2

def as_feature(self):
        r = [0.0] * self.feature_dimensionality()
        if self.value:
            if self.value <= 6:
                r[0] = 1.0
            else:
                r[1] = 1.0
        return r
```

Now we also need some training stories, so that Rasa Core can learn from these how to handle the different situations:
```yaml
# story1
...
* inform{"people": "3"}
  - action_book_table
...
# story2
* inform{"people": "9"}
  - action_explain_table_limit
```