# 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 or Hong Kong) 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. As mentioned above, for a `text` slot the value is irrelevant. 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"
```

There are multiple ways that slots are set during a conversation:

### 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.

### 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 like this:

```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](https://legacy-docs-v1.rasa.com/1.7.3/core/actions/#custom-actions). In this case, your stories need to include the slots.

```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"])]
```

### 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
```

- **Description:** The feature of this slot is set to `1` if a value with a list is set, where the list is not empty. If no value is set, or the empty list is the set value, the feature will be `0`.

#### 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
In the code below, we define a slot class called `NumberOfPeopleSlot`.

```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
```

```yaml
# story1
...
* inform{"people": "3"}
  - action_book_table
...
# story2
* inform{"people": "9"}
  - action_explain_table_limit
```

👋 I can help you get started with Rasa and answer your technical questions.