Rich can apply styles to patterns in text which you print() or 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 print() or log(), or by setting highlight=False on the 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 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 Theme.

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 RegexHighlighter is quite powerful, you can also extend its base class Highlighter to implement a custom scheme for highlighting. It contains a single method highlight which is passed the 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(f"color({randint(16, 255)})", index, index + 1)

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