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template: overrides/main.html
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# Code blocks

Code blocks and examples are an essential part of technical project
documentation. Material for MkDocs provides different ways to set up syntax
highlighting for code blocks, either during build time using [Pygments] or
during runtime using a JavaScript syntax highlighter.

  [Pygments]: https://pygments.org

## Configuration

This configuration enables syntax highlighting on code blocks and inline code 
blocks, and allows to include source code directly from other files. Add the 
following lines to `mkdocs.yml`

``` yaml
markdown_extensions:
  - pymdownx.highlight
  - pymdownx.inlinehilite
  - pymdownx.superfences
  - pymdownx.snippets
```

See additional configuration options:

- [Highlight]
- [InlineHilite]
- [SuperFences]
- [Snippets]

  [Highlight]: ../setup/extensions/python-markdown-extensions.md#highlight
  [InlineHilite]: ../setup/extensions/python-markdown-extensions.md#inlinehilite
  [SuperFences]: ../setup/extensions/python-markdown-extensions.md#superfences
  [Snippets]: ../setup/extensions/python-markdown-extensions.md#snippets

### Code annotations

[:octicons-heart-fill-24:{ .mdx-heart } Insiders][Insiders]{ .mdx-insiders } ·
:octicons-unlock-24: Feature flag ·
:octicons-beaker-24: Experimental ·
[:octicons-tag-24: insiders-2.2.0 ... present][Insiders]

Code annotations offer a comfortable and friendly way to attach arbitrary
content to specific sections of code blocks by adding numeric markers in block
and inline comments in the language of the block. Add the following to
`mkdocs.yml` to enable them globally:

``` yaml
theme:
  features:
    - content.code.annotate # (1)
```

1.  :man_raising_hand: I'm a code annotation! I can contain `code`, __formatted
    text__, images, ... basically anything that can be expressed in Markdown.

??? info "Enabling code annotations only for specific code blocks"

    If you don't want to enable code annotations globally, because you don't
    like the automatic inlining behavior, you can enable them for a specific
    code block by using a slightly different syntax based on the
    [Attribute List] extension:

    ```` yaml
    ``` { .yaml .annotate }
    # Code block content
    ```
    ````

    Note that the language shortcode which has to come first must now also be 
    prefixed by a `.`.

  [Insiders]: ../insiders/index.md
  [Attribute List]: ../setup/extensions/python-markdown.md#attribute-lists

## Usage

This section discusses how to use different syntax highlighting features with
[Pygments] – the default highlighter – so they don't apply when using
a JavaScript syntax highlighter.

### Specifying the language

Code blocks must be enclosed with two separate lines containing three backticks.
To add syntax highlighting to those blocks, add the language shortcode directly
after the opening block. See the [list of available lexers] to find the
shortcode for a given language.

_Example_:

```` markdown
``` python
import tensorflow as tf
```
````

_Result_:

``` python
import tensorflow as tf
```

  [list of available lexers]: https://pygments.org/docs/lexers/

### Adding annotations

Code annotations can be placed anywhere in a code block where a comment for the
language of the block can be placed, e.g. for JavaScript in `#!js // ...` and
`#!js /* ... */`, for Yaml `#!yaml # ...`, etc.[^1]

  [^1]:
    Code annotations require syntax highlighting with [Pygments] – they're
    currently not compatible with JavaScript syntax highlighters. Support will
    be added at a later point, allowing to always place code annotations at the
    end of lines.

_Example_:

```` markdown
``` yaml
theme:
  features:
    - content.code.annotate # (1)
```

1.  :man_raising_hand: I'm a code annotation! I can contain `code`, __formatted
    text__, images, ... basically anything that can be expressed in Markdown.
````

_Result_:

``` yaml
theme:
  features:
    - content.code.annotate # (1)
```

1.  :man_raising_hand: I'm a code annotation! I can contain `code`, __formatted
    text__, images, ... basically anything that can be expressed in Markdown.

### Adding line numbers

Line numbers can be added to a code block by using the `linenums="<start>"`
option directly after the shortcode, whereas `<start>` represents the starting
line number. A code block can start from a line number other than `1`, which
allows to split large code blocks for readability.

_Example_:

```` markdown
``` python linenums="1"
def bubble_sort(items):
    for i in range(len(items)):
        for j in range(len(items) - 1 - i):
            if items[j] > items[j + 1]:
                items[j], items[j + 1] = items[j + 1], items[j]
```
````

_Result_:

``` python linenums="1"
def bubble_sort(items):
    for i in range(len(items)):
        for j in range(len(items) - 1 - i):
            if items[j] > items[j + 1]:
                items[j], items[j + 1] = items[j + 1], items[j]
```

### Highlighting specific lines

Specific lines can be highlighted by passing the line numbers to the `hl_lines`
argument placed right after the language shortcode. Note that line counts start
at `1`, regardless of the starting line number specified as part of
[`linenums`][Adding line numbers].

=== "Line numbers"

    _Example_:

    ```` markdown
    ``` python hl_lines="2 3"
    def bubble_sort(items):
        for i in range(len(items)):
            for j in range(len(items) - 1 - i):
                if items[j] > items[j + 1]:
                    items[j], items[j + 1] = items[j + 1], items[j]
    ```
    ````

    _Result_:

    ``` python hl_lines="2 3"
    def bubble_sort(items):
        for i in range(len(items)):
            for j in range(len(items) - 1 - i):
                if items[j] > items[j + 1]:
                    items[j], items[j + 1] = items[j + 1], items[j]
    ```

=== "Line ranges"

    _Example_:

    ```` markdown
    ``` python hl_lines="2-5"
    def bubble_sort(items):
        for i in range(len(items)):
            for j in range(len(items) - 1 - i):
                if items[j] > items[j + 1]:
                    items[j], items[j + 1] = items[j + 1], items[j]
    ```
    ````

    _Result_:

    ``` python hl_lines="2-5"
    def bubble_sort(items):
        for i in range(len(items)):
            for j in range(len(items) - 1 - i):
                if items[j] > items[j + 1]:
                    items[j], items[j + 1] = items[j + 1], items[j]
    ```

  [Adding line numbers]: #adding-line-numbers

### Highlighting inline code blocks

When [InlineHilite] is enabled, syntax highlighting can be applied to inline
code blocks by prefixing them with a shebang, i.e. `#!`, directly followed by
the corresponding [language shortcode][list of available lexers].

_Example_:

``` markdown
The `#!python range()` function is used to generate a sequence of numbers.
```

_Result_:

The `#!python range()` function is used to generate a sequence of numbers.

### Embedding external files

When [Snippets] is enabled, content from other files can be embedded, which is particularly useful to reference and embed the contents of source files
directly in a document without copying.

_Example_:

```` markdown
```
--8<--​ ".browserslistrc"
```
````

_Result_:

```
last 4 years
```

## Customization

### Custom syntax theme

[:octicons-file-code-24: Source][Source] ·
:octicons-mortar-board-24: Difficulty: _easy_

If [Pygments] is used, Material for MkDocs provides the [styles for code blocks]
[Source], which are built with a custom and well-balanced palette that works
equally well for both [color schemes]:

- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-number-color) " } `--md-code-hl-number-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-special-color) " } `--md-code-hl-special-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-function-color) " } `--md-code-hl-function-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-constant-color) " } `--md-code-hl-constant-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-keyword-color) " } `--md-code-hl-keyword-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-string-color) " } `--md-code-hl-string-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-name-color) " } `--md-code-hl-name-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-operator-color) " } `--md-code-hl-operator-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-punctuation-color) " } `--md-code-hl-punctuation-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-comment-color) " } `--md-code-hl-comment-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-generic-color) " } `--md-code-hl-generic-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-variable-color) " } `--md-code-hl-variable-color`

Code block foreground, background and line highlight colors are defined via:

- :material-checkbox-blank-circle:{ style="color: var(--md-code-fg-color) " } `--md-code-fg-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-bg-color) " } `--md-code-bg-color`
- :material-checkbox-blank-circle:{ style="color: var(--md-code-hl-color) " } `--md-code-hl-color`

Let's say you want to change the color of `#!js "strings"`. While there are
several [types of string tokens], they use the same color. You can assign
a new color by using an [additional stylesheet]:

``` css
:root > * {
  --md-code-hl-string-color: #0FF1CE;
}
```

If you want to tweak a specific type of string, i.e. ``#!js `backticks` ``, you
can lookup the specific class name in the [syntax theme definition], and
override it as part of your additional stylesheet:

``` css
.highlight .sb {
  color: #0FF1CE;
}
```

  [Source]: https://github.com/squidfunk/mkdocs-material/blob/master/src/assets/stylesheets/main/_colors.scss
  [color schemes]: ../setup/changing-the-colors.md#color-scheme
  [types of string tokens]: https://pygments.org/docs/tokens/#literals
  [additional stylesheet]: ../customization.md#additional-css
  [syntax theme definition]: https://github.com/squidfunk/mkdocs-material/blob/master/src/assets/stylesheets/main/extensions/pymdownx/_highlight.scss