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Highlight

Overview

Highlight is an extension that adds support for code highlighting. Its purpose is to provide a single place to configure syntax highlighting for code blocks. Both InlineHilite and SuperFences can use Highlight to configure their highlight settings, but Highlight will also run all non-fence code blocks through the highlighter as well.

The Highlight extension is inspired by CodeHilite, but differs in features. PyMdown Extensions chooses not to implement special language headers for standard Markdown code blocks like CodeHilite does; PyMdown Extensions takes the position that language headers are better suited in fenced code blocks. So standard Markdown code blocks will just be styled as plain text unless guess_language is enabled. If you wish to highlight lines and define line numbers per code block, it is advised to use the SuperFences extension.

As previously mentioned, both InlineHilite's and SuperFences' highlighting can be controlled by Highlight. Both can use Pygments or JavaScript highlighters to do their code syntax highlighting, but all of the settings here only affect highlighting via Pygments except use_pygments and css_class. If you want to use a JavaScript syntax highlighter, set use_pygments to False or make sure you don't have Pygments installed.

The Highlight extension can be included in Python Markdown by using the following:

import markdown
md = markdown.Markdown(extensions=['pymdownx.highlight'])

Syntax Highlighting

If Pygments is installed, it will be the default syntax highlighter, but if it is not, or if use_pygments is turned off, code tags will be rendered in the HTML5 format for JavaScript highlighting:

<pre class="highlight"><code class="language-mylanguage"></code></pre>

Extended Pygments Lexer Options

If using Pygments, some lexers have special settings. For instance, the php lexer has the option startinline which, if enabled, will parse PHP syntax without requiring <? at the beginning. Highlight allows you to configure these settings via the option extend_pygments_lang.

extend_pygments_lang allows you to create a special Pygments alias language where you can configure the language settings to your liking. So if you wanted to enable startinline for php, you might create a language alias called php-inline that maps to php with startinline enabled. This would allow you to use php for normal PHP blocks, but also allow you to do inline PHP code without the block specifiers. You can also use extend_pygments_lang to completely override the base language's options – assuming your specified name overrides an existing name.

extend_pygments_lang an array of dictionaries. Each dictionary contains three keys: name which is the new name you are adding, lang which is the language the new name maps to, and options which is a dictionary of the options you wish to apply.

Highlight Example

To create the above mentioned php-inline, this example illustrates the configuration, and Markdown syntax you would use.

$a = array("foo" => 0, "bar" => 1);

`#!php-inline $a = array("foo" => 0, "bar" => 1);`
extended_pygments_lang = [
    {"name": "php-inline", "lang": "php", "options": {"startinline": True}}
]

Line Number Styles

Pygments has two available styles when outputting source code with line numbers enabled: table and inline. table is the default output and creates a table output for lines with numbers. inline places the line numbers directly in the source code output and can sometimes be undesirable as copy and paste will always copy the line numbers as well.

The Highlight extension provides a third line number style called pymdownx-inline. Instead of writing line numbers directly in the pre like Pygments' default inline style does, it writes the line numbers as <span class="lineno" data-linenos="1 "></span>. This way the line numbers are un-selectable and can be displayed with CSS:

[data-linenos]:before {
  content: attr(data-linenos);
}

Line number styles are set with the option linenums_style as described in Options.

Options

Option Type Default Description
css_class string 'highlight Default class to apply to the wrapper element on code blocks. Other extensions can override this.
guess_lang bool False Guess what syntax language should be used if no language is specified.
pygments_style string 'default' Set the Pygments' style to use. This really only has an effect when used with noclasses.
noclasses bool False This will cause the styles to directly be written to the tag's style attribute instead of requiring a stylesheet.
use_pygments bool True Controls whether Pygments (if available) is used to style the code, or if the code will just be escaped and prepped for a JavaScript syntax highlighter.
linenums bool None Enable line numbers globally for block code. This will be ignored for inline code. If set to False line numbers will be disabled globally and can not be turned on, not even per code block.
linenums_special int 1 Globally sets the specified nth lines' gutter with the class "special". This can be overridden in SuperFences per fence if desired.
linenums_style string 'table' Controls the output style when linenums are enabled. Supported styles are Pygments default table and inline, but also supported is the pymdown-extensions pymdownx-inline which provides a special inline mode, see Line Number Styles for more info.
linenums_class string 'linenums' Controls the name of the line number class when Pygments is not used.
extend_pygments_lang list [] A list of extended languages to add. See Extended Pygments Lexer Options for more info.
legacy_no_wrap_code bool False A temporary option provided during the transition period to the new output format. From now on, all block code under pre elements will be wrapped in a code element as well under Pygments 2.4+. This disables this format. This option will be removed in the future.
language_prefix string 'language-' Controls the prefix applied to the language class when Pygments is not used. By default, uses the HTML5 language-.

New 6.2

legacy_no_wrap_code was added in 6.3, but is only provided to help transition to the format when using Pygments 2.4+. This option will be removed in the future.

New 7.1

linenums_class was added in 7.1.

New 7.2

linenums now accepts None as the default for allow line numbers to be enabled per code block. False now disables line numbers globally preventing line numbers even if specified per code block. True still enables globally.


Last update: August 3, 2020