Expose Formatters via API and Improve Documentation

[WillAyd]

See the discussion in #22759 (comment) - we could potentially expose the formatters via the public API and allow users to subclass them or even assign properties to them which give finer control over what gets exported.

I've had an actual use case for this for at least the ExcelFormatter to change the exported header formatting. Haven't had as much of a use case for other Formatters but would love input

[geoffrey-eisenbarth]

Has there been any progress on this? I ended up just changing the new header_style property to return None in the source so I can to have full control of formatting with XlsxWriter. Not ideal, but gives me what I need for now.

Is there a more appropriate way to do this?

[WillAyd]

No community PRs against it to date - would certainly welcome a contribution from you if you’d like to try

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On Apr 3, 2019, at 1:34 PM, Geoffrey B. Eisenbarth ***@***.***> wrote: Has there been any progress on this? I ended up just changing the new header_style property to return None in the source so I can to have full control of formatting with XlsxWriter. Not ideal, but gives me what I need for now. Is there a more appropriate way to do this? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or mute the thread.

[geoffrey-eisenbarth]

I would love to contribute, I'll look more into the relevant code tonight and tomorrow.

[johncthomas]

So I spent half a day trying to write a workaround to this that failed in certain cases so I should probably fix it in the source code. I've never contributed to an open source project so here's what I'm thinking in case I'm planning something dumb:

• Add header_format & index_format args to DataFrame.to_excel with default value of pandas.io.formats.excel.ExcelFormatter.header_style

• Change ExcelFormatter to implement any passed style dict, or None with no formatting applied

edit: Oh, I'm only talking about the header/index formatters, looks like the scope of this issue is wider and I don't really know what people are looking for there.