rich/docs/source/highlighting.rst

Highlighting
============

Rich can apply styles to patterns in text which you :meth:`~rich.console.Console.print` or :meth:`~rich.console.Console.log`. With the default settings, Rich will highlight things such as numbers, strings, collections, booleans, None, and a few more exotic patterns such as URLs and UUIDs.

You can disable highlighting either by setting ``highlight=False`` on :meth:`~rich.console.Console.print` or :meth:`~rich.console.Console.log`, or by setting ``highlight=False`` on the :class:`~rich.console.Console` constructor which disables it everywhere. If you disable highlighting on the constructor, you can still selectively *enable* highlighting with ``highlight=True`` on print/log.


Custom Highlighters
-------------------

If the default highlighting doesn't fit your needs, you can define a custom highlighter. The easiest way to do this is to extend the :class:`~rich.highlighter.RegexHighlighter` class which applies a style to any text matching a list of regular expressions.

Here's an example which highlights text that looks like an email address::

    from rich.console import Console  
    from rich.highlighter import RegexHighlighter      
    from rich.theme import Theme

    class EmailHighlighter(RegexHighlighter):
        """Apply style to anything that looks like an email."""

        base_style = "example."
        highlights = [r"(?P<email>[\w-]+@([\w-]+\.)+[\w-]+)"]


    theme = Theme({"example.email": "bold magenta"})
    console = Console(highlighter=EmailHighlighter(), theme=theme)
    console.print("Send funds to money@example.org")


The ``highlights`` class variable should contain a list of regular expressions. The group names of any matching expressions are prefixed with the ``base_style`` attribute and used as styles for matching text. In the example above, any email addresses will have the style "example.email" applied, which we've defined in a custom :ref:`Theme <themes>`.

Setting the highlighter on the Console will apply highlighting to all text you print (if enabled). You can also use a highlighter on a more granular level by using the instance as a callable and printing the result. For example, we could use the email highlighter class like this::


    console = Console(theme=theme)
    highlight_emails = EmailHighlighter()
    console.print(highlight_emails("Send funds to money@example.org"))


While :class:`~rich.highlighter.RegexHighlighter` is quite powerful, you can also extend its base class :class:`~rich.highlighter.Highlighter` to implement a custom scheme for highlighting. It contains a single method :class:`~rich.highlighter.Highlighter.highlight` which is passed the :class:`~rich.text.Text` to highlight.

Here's a silly example that highlights every character with a different color::

    from random import randint

    from rich import print
    from rich.highlighter import Highlighter


    class RainbowHighlighter(Highlighter):
        def highlight(self, text):
            for index in range(len(text)):
                text.stylize(str(randint(16, 255)), index, index + 1)


    rainbow = RainbowHighlighter()
    print(rainbow("I must not fear. Fear is the mind-killer."))