ENH: Add ability to style axis names with Styler

[tehunter]

• closes ENH: Styler apply_index and format_index applicable to index names  #48936
  • apply_index
  • format_index
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.
• Added documentation to Table Visualization page

cc: @attack68

[tehunter]

 column_name = [ _element( "th", ( f"{self.css['blank']} {self.css['level']}{r}" if name is None else f"{self.css['columns_name']} {self.css['level']}{r}" ), name if (name is not None and not self.hide_column_names) else self.css["blank_value"], not all(self.hide_index_), ) ]

Is this a breaking change? For column level names, it removes the index_name class and adds in the columns_names class in it's place. If users were purposefully doing styles with .index_name selectors with the intention of applying those to column level names, it will break that behavior.

[attack68]

Well it will break the example in the user guide because that styles class index_name.

However, this should be an easy fix:

index_names = { 'selector': '.index_name, .col_name', 'props': 'font-style: italic; color: darkgrey; font-weight:normal;' } 

As long as this break is documented I think including the additional functionality is worth it in long run.

[attack68]

Suggested change

	"columns_name": "columns_name",
	"col_name": "col_name",

[attack68]

Suggested change

	"columns_name": "columns_name",
	"col_name": "col_name",

[attack68]

is this following the same pattern as above?

[attack68]

I think this PR looks good but there are a few things to check off:

• editing the styler guide documentation and any other locations for the list of CSS classes that are added in the HTML: col_name is a new one.
• although we are re-using the apply and applymap methods with a small extension it is rather overkill to suggest that one would actually use a function to style these. It is probably easier just to supply a small list of styles to each name (of which there are probably a small number). In that case a simple documentation entry might help, something like:

styler.apply_index(lambda s: ["color: blue;", "color: red;"], names=True) 

should suffice.

• all other column CSS class names have col so I suggested sticking with the format.
• needs a whats new and a version added for the argument, and a note about minor breaking change.
• the copying mechanics are also changed. should review the docs there to see if it should be added.
• the tests seem to be for multiindexes. Does it also work just in the regular index case?

[github-actions]

This pull request is stale because it has been open for thirty days with no activity. Please update and respond to this comment if you're still interested in working on this.

[tehunter]

This pull request is stale because it has been open for thirty days with no activity. Please update and respond to this comment if you're still interested in working on this.

Still working on this

[tehunter]

Note to self on current progress:

• Completed implementation of ENH: Add ability to style axis names with Styler #48972 (comment) except for checking the copy mechanics
• Need to generate and check documentation, specifically example output and style user guide (version added)
• Need to validate basic Index behavior and test completeness

[mroeschke]

Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen.