> ## Documentation Index
> Fetch the complete documentation index at: https://bazel-pr-29804.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# list

The built-in list type. Example list expressions:

```
x = [1, 2, 3]
```

Accessing elements is possible using indexing (starts from `0`):

```
e = x[1]   # e == 2
```

Lists support the `+` operator to concatenate two lists. Example:

```
x = [1, 2] + [3, 4]   # x == [1, 2, 3, 4]
x = ["a", "b"]
x += ["c"]            # x == ["a", "b", "c"]
```

Similar to strings, lists support slice operations:

```
['a', 'b', 'c', 'd'][1:3]   # ['b', 'c']
['a', 'b', 'c', 'd'][::2]  # ['a', 'c']
['a', 'b', 'c', 'd'][3:0:-1]  # ['d', 'c', 'b']
```

Lists are mutable, as in Python.

## Members

* [append](#append)
* [clear](#clear)
* [extend](#extend)
* [index](#index)
* [insert](#insert)
* [pop](#pop)
* [remove](#remove)

## append

```
None list.append(item)
```

Adds an item to the end of the list.

### Parameters

| Parameter | Description |
| --------- | ----------- |
| `item`    | required    |

## clear

```
None list.clear()
```

Removes all the elements of the list.

## extend

```
None list.extend(items)
```

Adds all items to the end of the list.

### Parameters

| Parameter | Description |
| --------- | ----------- |
| `items`   | required    |

## index

```
int list.index(x, start=None, end=None)
```

Returns the index in the list of the first item whose value is x. It is an error if there is no such item.

### Parameters

| Parameter | Description                                                                                                              |
| --------- | ------------------------------------------------------------------------------------------------------------------------ |
| `x`       | required                                                                                                                 |
| `start`   | [int](/versions/7.7.1/rules/lib/core/int); or `None`; default is `None`  The start index of the list portion to inspect. |
| `end`     | [int](/versions/7.7.1/rules/lib/core/int); or `None`; default is `None`  The end index of the list portion to inspect.   |

## insert

```
None list.insert(index, item)
```

Inserts an item at a given position.

### Parameters

| Parameter | Description                                |
| --------- | ------------------------------------------ |
| `index`   | required  The index of the given position. |
| `item`    | required  The item.                        |

## pop

```
unknown list.pop(i=-1)
```

Removes the item at the given position in the list, and returns it. If no `index` is specified, it removes and returns the last item in the list.

### Parameters

| Parameter | Description                                                                                   |
| --------- | --------------------------------------------------------------------------------------------- |
| `i`       | [int](/versions/7.7.1/rules/lib/core/int); or `None`; default is `-1`  The index of the item. |

## remove

```
None list.remove(x)
```

Removes the first item from the list whose value is x. It is an error if there is no such item.

### Parameters

| Parameter | Description                     |
| --------- | ------------------------------- |
| `x`       | required  The object to remove. |