Repeat headings every n-th row in Jupyter-lab notebook

[elisamalzoni]

• closes Pandas - Repeat headings every n-th row in Jupyter-lab notebook #27563
• tests added / passed
• passes black pandas
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

Adds a new option in pd.set_option() method.

Usage:

# n is an int that represents the interval of rows which the headers are repeated (default = 0, no repetition)
pd.set_option("display.repeating_row_index", n)   

Before	After (n = 3)

@Leostayner

[pep8speaks]

Hello @elisamalzoni! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2019-08-22 14:55:02 UTC

[TomAugspurger]

Hmm, I'm not entirely sure about this. It doesn't mesh well with my idea of an HTML table.

If we proceed, we'd need tests, and we would need to handle it similar to the other options (a parameter that gets plumbed through from DataFrame.to_html down to the formatter, and looked up from the config if not specified)

[WillAyd]

Yea I think this is a little arbitrary. From the linked issue I get the problem we are trying to solve is that the headers aren't visible while scrolling through. Wouldn't it be possible to just pin the headers then with appropriate CSS?

cc @simonjayhawkins for insights

[simonjayhawkins]

I do think that this could be out-of-scope for pandas. presumably, it's an issue for any application/library display HTML in the notebook and the issue should be raised there?

[simonjayhawkins]

@elisamalzoni will look in detail, but on initially glance suspect that this may have issues with a multiIndex because of rowspan. Changes to _write_hierarchical_rows would also be needed. Can you add a test for this?

[gfyoung]

I agree that pinning is a preferable option to resolving this issue.

[WillAyd]

Thanks all for the input. Given there doesn't appear to be a lot of appetite for this from the maintainers I think going to close, but @elisamalzoni appreciate for sure the effort on this and would welcome that on any other issues out there