STYLE, TYP frame-or-series-union check no longer relevant

[MarcoGorelli]

This check is no longer relevant:

pandas/.pre-commit-config.yaml

Lines 83 to 88 in 9ab55b4

	- id: frame-or-series-union
	name: Check for use of Union[Series, DataFrame] instead of FrameOrSeriesUnion alias
	entry: Union\[.*(Series,.*DataFrame|DataFrame,.*Series).*\]
	language: pygrep
	types: [python]
	exclude: ^pandas/_typing\.py$

Since using PEP604 rewrites, this would be written as

x: Series | DataFrame

anyway.

x: FrameOrSeriesUnion

is actually just as long as the above, and arguably less explicit.

---

@simonjayhawkins thoughts on replacing all the FrameOrSeriesUnion occurrences, removing the alias, and removing the above check?

[simonjayhawkins]

+1

[mohansaimandalapu]

Hi MarcoGorelli

I would like to take up this issue, this is my first open source PR, I couldn't understand the issue completely. It would be great if you can elucidate it. Thank you

[MarcoGorelli]

Sure. At the moment, we alias DataFrame | Series as FrameOrSeriesUnion, the issue is simply to remove the alias. So:

1. remove this check:

   pandas/.pre-commit-config.yaml

   Lines 83 to 88 in 895f0b4

   	- id: frame-or-series-union
   	name: Check for use of Union[Series, DataFrame] instead of FrameOrSeriesUnion alias
   	entry: Union\[.*(Series,.*DataFrame|DataFrame,.*Series).*\]
   	language: pygrep
   	types: [python]
   	exclude: ^pandas/_typing\.py$

2. remove this alias:

   pandas/pandas/_typing.py

   Lines 97 to 101 in 895f0b4

   	# FrameOrSeriesUnion means either a DataFrame or a Series. E.g.
   	# `def func(a: FrameOrSeriesUnion) -> FrameOrSeriesUnion: ...` means that if a Series
   	# is passed in, either a Series or DataFrame is returned, and if a DataFrame is passed
   	# in, either a DataFrame or a Series is returned.
   	FrameOrSeriesUnion = Union["DataFrame", "Series"]

3. Anywhere in the codebase which uses this alias, replace it with DataFrame | Series

If anything is unclear, please do ask :)

[Swanand01]

Hello @MarcoGorelli, first time contributor here. I would like to take up this issue.
If I understand correctly, the check and alias have to be removed, and all instances of FrameOrSeriesUnion in the codebase have to be replaced with Series | DataFrame.
Thank you.

[joonlim9]

take

[MarcoGorelli]

I think @mohansaimandalapu is already working on this

[joonlim9]

I think @mohansaimandalapu is already working on this
I thought multiple contributors on a single issue is allowed, my bad.

[MarcoGorelli]

I think @mohansaimandalapu is already working on this
I thought multiple contributors on a single issue is allowed, my bad.

Hey @joonlim9 - it doesn't look like they're working on it

Anyone is free to work on this now

[Anupam-USP]

PR is merged so is this issue closed? @MarcoGorelli