Highlighting text ranges with Rich | python
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Today I've been playing with py-tree-sitter a bit and I wanted to highlight match ranges, but was unable to figure out how to do it with rich, so I reached...

Date: August 24, 2022

Today I’ve been playing with py-tree-sitter <https://github.com/tree-sitter/py-tree-sitter> a bit and I wanted to highlight match ranges, but was unable to figure out how to do it with rich <https://github.com/Textualize/rich>, so I reached out to @textualizeio <https://twitter.com/textualizeio> for help.

https://twitter.com/_WaylonWalker/status/1562469770766589952

While waiting for that reply let’s show how we got this far.

imports
───────

Lets import all the classes that we need from rich <https://github.com/Textualize/rich> and setup a console to print to.

[code]
  from rich.console import Console
  from rich.syntax import Syntax
  from rich.style import Style

  console = Console()

some code
─────────

Now we need some code to highlight. I am going to rip my register_pipeline from another post <https://waylonwalker.com/designing-kedro-router>.

[code]
  code = '''
  from find_kedro import find_kedro
  
  def register_pipelines(self) -> Dict[str, Pipeline]:
      """Register the project's pipeline.
      Returns:
          A mapping from a pipeline name to a ``Pipeline`` object.
      """
      return find_kedro()
  '''

print
─────

We could simply print out the code we have as a variable, but thats a bit hard to read.

Image: print-register-pipelines.webp <https://dropper.waylonwalker.com/api/file/765c471d-990f-4c7c-9c99-7a039c4db900.webp>

console.print
─────────────

printing with rich <https://github.com/Textualize/rich>’s console makes it a little better, but not much by default.

Image: console-print-register-pipelines.webp <https://dropper.waylonwalker.com/api/file/b946c8b4-c1f0-4d58-8709-90c8f95a1f77.webp>

Syntax
──────

We can pull from rich <https://github.com/Textualize/rich>’s syntax module to really pretty this up.

[code]
  syntax = Syntax(code, 'python', line_numbers=True)
  console.print(syntax)

Image: syntax-print-register-pipelines.webp <https://dropper.waylonwalker.com/api/file/f9329423-c0f5-4263-b241-b8f470fc758c.webp>

Now we are getting some really impressive print outs right in the terminal!

│ note that I have ipython set to use rich <https://github.com/Textualize/rich>, you will need to console.print() in scripts

highlight lines
───────────────

Now we can start highlighting lines right when we initialize our Syntax instance. It looks ok. It’s not super visible, but more importantly its not granular enough. I want to highlight specific ranges like the word register_pipelines.

[code]
  syntax = Syntax(code, 'python', line_numbers=True, highlight_lines=[4])
  console.print(syntax)

Image: syntax-print-register-pipelines-highlight-line.webp <https://dropper.waylonwalker.com/api/file/20b4564e-3a08-4e5a-9bed-cda07779c8fb.webp>

This hows the line, but still is not very accurate.

highlight text
──────────────

[@textualizeio] got back to me, let’s see if What we can do with stylize_range!

https://twitter.com/textualizeio/status/1562487302274043904

[code]
  syntax = Syntax(code, 'python', line_numbers=True)
  style = Style(bgcolor='deep_pink4')
  syntax.stylize_range(style, (4, 4), (4, 22))
  console.print(syntax)

This gives us the final result we are looking for, we can easily see what is being targeted here. In this case the function name register_pipelines.

Image: syntax-highlight-range-register-pipelines.webp <https://dropper.waylonwalker.com/api/file/b5f27c34-6ffe-425c-b2df-8ade7c5b6f8b.webp>

This turns out to be exacly what I am looking for. Now I have an easy way to print out highlighted code wtih my py-tree-sitter <https://github.com/tree-sitter/py-tree-sitter> query results.

Links
─────

- @textualizeio
- another post
- py-tree-sitter
- rich