ENH: write Styler rendered output to file

[jorisvandenbossche]

I was answering a question on conditional formatting of html on SO.

So the OP was using to_html but wanted conditional formatting. Therefore, I pointed to Styler to do this more easily than using the formatters argument in to_html, but when you have a Styler object, there is no longer a to_html method to write the result to a html file.

Of course you can write the result of render manually to a file, but would this ability be a desired enhancement?

• Maybe we can add a to_file method to Styler? (to_html seems a bit specific, if we also want to use the Styler for other formats such as latex in the future)
• Alternatively, we could add a style option in to_html where you can pass a Styler object?

Related to #11610

@TomAugspurger

[jreback]

xref to #11700 as well

[TomAugspurger]

Another option is to take a buf_or_file in Styler.render, to match the to_html behavior. +1 to that or a to_file method.

For now I'd say just write the output of .render, but we could eventually add options for writing a standalone document, including other CSS files.

[toobaz]

This branch adds a to_html method. I used it a couple of times, but to be honest I don't remember whether it worked fine or had relevant issues.

Maybe we can add a to_file method to Styler? (to_html seems a bit specific, if we also want to use the Styler for other formats such as latex in the future)

I assumed the Styler could just have the output methods that DataFrame itself has.... but indeed this is not a good approach if we plan to massively/cheaply enlarge the number of supported formats, i.e. by relying on external converting libraries.

[jorisvandenbossche]

I assumed the Styler could just have the output methods that DataFrame itself has...

That depends a bit on how we see the Styler (I didn't use it lately, so I can't really remember). Would one Styler object both support to html and to latex, or would you rather have a Styler class for to html and a Styler class for to latex? (as the templates are different, many methods will have to add different syntax, ..)

[toobaz]

would you rather have a Styler class for to html and a Styler class for to latex?

I admit I hadn't even considered this option.

as the templates are different, many methods will have to add different syntax

Not sure I understand what a template is. Do you think that, say, the syntax of Style.to_latex should be different from a mere combination of the syntax of Style.to_html and the syntax of DataFrame.to_latex?

In particular, I never thought about having parameters in to_latex map to specific LaTeX formatting commands, because to my eyes not being able to transparently change the backend would defeat the purpose of supporting multiple backends. I rather see a set of supported formatting options which default to CSS ones (with, in the future, some additions if required), and other methods as a translation between CSS "language" and the desired format. Then CSS is huge, so each method would have in the docs a list of attributes it actually supports.