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BUG: SeriesGroupBy.apply sets name attribute if result is DataFrame #49908

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Merged
merged 4 commits into from
Nov 27, 2022
Merged

BUG: SeriesGroupBy.apply sets name attribute if result is DataFrame #49908

merged 4 commits into from
Nov 27, 2022

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MarcoGorelli
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@MarcoGorelli MarcoGorelli added Bug Groupby Apply Apply, Aggregate, Transform, Map labels Nov 25, 2022
@MarcoGorelli MarcoGorelli force-pushed the grp-apply-sets-name branch 2 times, most recently from a1b2edf to c863f89 Compare November 25, 2022 15:00
@MarcoGorelli MarcoGorelli added Regression Functionality that used to work in a prior pandas version and removed Bug labels Nov 25, 2022
rhshadrach
rhshadrach requested changes Nov 25, 2022
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Looking good!
pandas/core/groupby/generic.py
@@ -401,7 +401,8 @@ def _wrap_applied_output(
not_indexed_same=not_indexed_same,
is_transform=is_transform,
)
result.name = self.obj.name
if isinstance(result, Series):
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Can you use result.ndim == 1 here instead.
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sure, will do - though just for my understanding, why?
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@rhshadrach rhshadrach Nov 25, 2022 •
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Interesting - it used to be that isinstance checks were quite a bit more expensive than checking the ndim attribute; I'm now seeing isinstance is slightly cheaper. With type checkers able to naturally derive type information from isinstance checks in code paths, we should certainly prefer isinstance if they are just as performant.
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@MarcoGorelli - I'm good with either using ndim or isinstance here; I plan on taking a more in depth look of our usage. Let me know what you think.
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no preference from my end
@rhshadrach rhshadrach added this to the 1.5.3 milestone Nov 27, 2022
@rhshadrach rhshadrach added the Bug label Nov 27, 2022
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@MarcoGorelli I added back the Bug tag. I've been doing that on regressions to differ between e.g. a performance regression and a behavior regression. Let me know if you think differently.
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@MarcoGorelli I added back the Bug tag. I've been doing that on regressions to differ between e.g. a performance regression and a behavior regression. Let me know if you think differently.

Hey - sounds good to me
rhshadrach
rhshadrach approved these changes Nov 27, 2022
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lgtm
@rhshadrach rhshadrach merged commit 15e6abd into pandas-dev:main Nov 27, 2022
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Thanks @MarcoGorelli!
@meeseeksmachine meeseeksmachine mentioned this pull request Nov 27, 2022
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meeseeksmachine pushed a commit to meeseeksmachine/pandas that referenced this pull request Nov 27, 2022
@MarcoGorelli @meeseeksmachine
Backport PR pandas-dev#49908: BUG: SeriesGroupBy.apply sets name attr…
b7f105a 
…ibute if result is DataFrame
MarcoGorelli added a commit that referenced this pull request Nov 27, 2022
@meeseeksmachine @MarcoGorelli
Backport PR #49908 on branch 1.5.x ( BUG: SeriesGroupBy.apply sets na…
071bd27 
…me attribute if result is DataFrame) (#49928)

Backport PR #49908:  BUG: SeriesGroupBy.apply sets name attribute if result is DataFrame

Co-authored-by: Marco Edward Gorelli <33491632+MarcoGorelli@users.noreply.github.com>
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Labels
Apply Apply, Aggregate, Transform, Map Bug Groupby Regression Functionality that used to work in a prior pandas version
2 participants
@MarcoGorelli @rhshadrach