# Dictionary Access

To get the value for a specific key from a dictionary, the access syntax can be used: The dictionary is followed by an opening square bracket `[`, the key, and ends with a closing square bracket `]`.

Accessing a key returns an optional: If the key is found in the dictionary, the value for the given key is returned, and if the key is not found, `nil` is returned.

```
// Declare a constant that has type `{Bool: Int}`,
// a dictionary mapping integers to booleans.
//
let booleans = {
    1: true,
    0: false
}

// The result of accessing a key has type `Bool?`.
//
booleans[1]  // is `true`
booleans[0]  // is `false`
booleans[2]  // is `nil`

// Invalid: Accessing a key which does not have type `Int`.
//
booleans["1"]
```

```
// Declare a constant that has type `{Bool: Int}`,
// a dictionary mapping booleans to integers.
//
let integers = {
    true: 1,
    false: 0
}

// The result of accessing a key has type `Int?`
//
integers[true] // is `1`
integers[false] // is `0`
```

To set the value for a key of a dictionary, the access syntax can be used as well.

```
// Declare a constant that has type `{Int: Bool}`,
// a dictionary mapping booleans to integers.
//
let booleans = {
    1: true,
    0: false
}

// Assign new values for the keys `1` and `0`.
//
booleans[1] = false
booleans[0] = true
// `booleans` is `{1: false, 0: true}`
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://max-daunarovich.gitbook.io/flow-network/introduction/values-and-types/dictionaries/dictionary-access.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.