ENH: Styler.highlight_null can accepts subset argument

[immaxchen]

As proposed in #31345 and as a follow-up PR for #29118

• closes ENH: Styler.highlight_null to accept subset argument #31345
• tests added / passed
• passes black pandas
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[MarcoGorelli]

I know this was already absent, but should the default (red) be mentioned here in the docstring?

[immaxchen]

sure~

[WillAyd]

This isn't an IndexSlice right? Just a label or list of labels?

[immaxchen]

It is an IndexSlice, since it calls self.applymap and applymap uses IndexSlice.

< code >

pandas/pandas/io/formats/style.py

Lines 729 to 736 in e22a656

	def _applymap(self, func: Callable, subset=None, **kwargs) -> "Styler":
	func = partial(func, **kwargs) # applymap doesn't take kwargs?
	if subset is None:
	subset = pd.IndexSlice[:]
	subset = _non_reducing_slice(subset)
	result = self.data.loc[subset].applymap(func)
	self._update_ctx(result)
	return self

< proof >

< the doc >

[WillAyd]

The test case here though is not for an IndexSlice rather a list of labels. I think for a natural API should go with Label / Sequence of Labels as mentioned above

[immaxchen]

It can take Label / Sequence of Labels as well, just like other Styler built-in methods.

[WillAyd]

Can you update this to label or list of labels?

[immaxchen]

sure.

[WillAyd]

Can you update this to label or list of labels?

[WillAyd]

minor nit on annotation otherwise lgtm

@TomAugspurger care to look?

[TomAugspurger]

Won't have time near-term to look.

…

On Tue, Mar 3, 2020 at 7:24 PM William Ayd ***@***.***> wrote: ***@***.**** requested changes on this pull request. minor nit on annotation otherwise lgtm @TomAugspurger <https://github.com/TomAugspurger> care to look? ------------------------------ In pandas/io/formats/style.py <#31350 (comment)>: > @@ -1003,19 +1003,23 @@ def hide_columns(self, subset) -> "Styler": def _highlight_null(v, null_color: str) -> str: return f"background-color: {null_color}" if pd.isna(v) else "" - def highlight_null(self, null_color: str = "red") -> "Styler": + def highlight_null(self, null_color: str = "red", subset=None) -> "Styler": ⬇️ Suggested change - def highlight_null(self, null_color: str = "red", subset=None) -> "Styler": + def highlight_null(self, null_color: str = "red", subset: Optional[Union[Label, Sequence[Label]]]=None) -> "Styler": — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#31350?email_source=notifications&email_token=AAKAOIVIA555AZZ3BF32TA3RFWUUFA5CNFSM4KMDQDK2YY3PNVWWK3TUL52HS4DFWFIHK3DMKJSXC5LFON2FEZLWNFSXPKTDN5WW2ZLOORPWSZGOCX3AUCA#pullrequestreview-368445960>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAKAOIXD3STROVYY3QN3RKLRFWUUFANCNFSM4KMDQDKQ> .

[TomAugspurger]

LGTM once the CI issue is sorted out.

[immaxchen]

Thanks, it's ok now.

[WillAyd]

Thanks @immaxchen nice PR!