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GH1671 Improve testing for Transformation/Reduction methods on Groupby #1672

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GH1671 Improve testing for Transformation/Reduction methods on Groupby #1672

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171 changes: 171 additions & 0 deletions tests/test_groupby.py
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Original file line number Diff line number Diff line change
Expand Up @@ -31,9 +31,12 @@
RollingGroupby,
)

from pandas.errors import Pandas4Warning

from tests import (
TYPE_CHECKING_INVALID_USAGE,
check,
pytest_warns_bounded,
)

if TYPE_CHECKING:
Expand Down Expand Up @@ -925,3 +928,171 @@ def test_frame_groupby_aggregate() -> None:

check(assert_type(df.groupby("b").agg(a=("a", "mean")), DataFrame), DataFrame)
check(assert_type(df.groupby("b").agg(**dico), DataFrame), DataFrame)


def test_frame_groupby_transform_reduction_kernels() -> None:
"""Test DataFrameGroupBy.transform with ReductionKernelType literals."""
check(assert_type(GB_DF.transform("all"), DataFrame), DataFrame)
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@cmp0xff cmp0xff Feb 13, 2026

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I think for DataFrame.transform, all str's are accepted by the stubs at the moment. Shall we switch to a Literal and also add one or two negative tests in TYPE_CHECKING_INVALID_USAGE?

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@loicdiridollou loicdiridollou Feb 13, 2026

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Happy to make the switch, I was just worried there are some functions not in the list and we would break for the user. What do you think? Should we take the risk?

check(assert_type(GB_DF.transform("any"), DataFrame), DataFrame)
with pytest_warns_bounded(Pandas4Warning, "corrwith is deprecated", lower="2.99"):
check(assert_type(GB_DF.transform("corrwith", other=DF), DataFrame), DataFrame)
Comment on lines +937 to +938
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@cmp0xff cmp0xff Feb 13, 2026

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We don't support 2.x anymore, do we?

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@loicdiridollou loicdiridollou Feb 13, 2026

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in pytest_warns_bounded the check for version is strict so if you put 3.0 it will not trigger for the 3.0 version, that way I am forced to stick to 2.99. (we had the issue in a different PR).

check(assert_type(GB_DF.transform("count"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("first"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("idxmax"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("idxmin"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("last"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("max"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("mean"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("median"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("min"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("nunique"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("prod"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("quantile"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("sem"), DataFrame), DataFrame)
# TODO: pandas-dev/pandas-stubs#1671, size, cumcount, ngroup return Series at runtime on DataFrameGroupBy
check(assert_type(GB_DF.transform("skew"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("std"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("sum"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("var"), DataFrame), DataFrame)


def test_frame_groupby_transform_transformation_kernels() -> None:
"""Test DataFrameGroupBy.transform with TransformationKernelType literals."""
check(assert_type(GB_DF.transform("bfill"), DataFrame), DataFrame)
# TODO: pandas-dev/pandas-stubs#1671, cumcount and ngroup return Series at runtime on DataFrameGroupBy
check(assert_type(GB_DF.transform("cummax"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("cummin"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("cumprod"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("cumsum"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("diff"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("ffill"), DataFrame), DataFrame)
# TODO: pandas-dev/pandas-stubs#1671, fillna is not a valid function name for transform(name) at runtime
check(assert_type(GB_DF.transform("pct_change"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("rank"), DataFrame), DataFrame)
check(assert_type(GB_DF.transform("shift"), DataFrame), DataFrame)


def test_series_groupby_transform_reduction_kernels() -> None:
"""Test SeriesGroupBy.transform with ReductionKernelType literals."""
check(assert_type(GB_S.transform("all"), Series), Series)
check(assert_type(GB_S.transform("any"), Series), Series)
# TODO: pandas-dev/pandas-stubs#1671, corrwith does not exist on SeriesGroupBy
check(assert_type(GB_S.transform("count"), Series), Series)
check(assert_type(GB_S.transform("first"), Series), Series)
check(assert_type(GB_S.transform("idxmax"), Series), Series)
check(assert_type(GB_S.transform("idxmin"), Series), Series)
check(assert_type(GB_S.transform("last"), Series), Series)
check(assert_type(GB_S.transform("max"), Series), Series)
check(assert_type(GB_S.transform("mean"), Series), Series)
check(assert_type(GB_S.transform("median"), Series), Series)
check(assert_type(GB_S.transform("min"), Series), Series)
check(assert_type(GB_S.transform("nunique"), Series), Series)
check(assert_type(GB_S.transform("prod"), Series), Series)
check(assert_type(GB_S.transform("quantile"), Series), Series)
check(assert_type(GB_S.transform("sem"), Series), Series)
check(assert_type(GB_S.transform("size"), Series), Series)
check(assert_type(GB_S.transform("skew"), Series), Series)
check(assert_type(GB_S.transform("std"), Series), Series)
check(assert_type(GB_S.transform("sum"), Series), Series)
check(assert_type(GB_S.transform("var"), Series), Series)


def test_series_groupby_transform_transformation_kernels() -> None:
"""Test SeriesGroupBy.transform with TransformationKernelType literals."""
check(assert_type(GB_S.transform("bfill"), Series), Series)
check(assert_type(GB_S.transform("cumcount"), Series), Series)
check(assert_type(GB_S.transform("cummax"), Series), Series)
check(assert_type(GB_S.transform("cummin"), Series), Series)
check(assert_type(GB_S.transform("cumprod"), Series), Series)
check(assert_type(GB_S.transform("cumsum"), Series), Series)
check(assert_type(GB_S.transform("diff"), Series), Series)
check(assert_type(GB_S.transform("ffill"), Series), Series)
# TODO: pandas-dev/pandas-stubs#1671, fillna is not a valid function name for transform(name) at runtime
check(assert_type(GB_S.transform("ngroup"), Series), Series)
check(assert_type(GB_S.transform("pct_change"), Series), Series)
check(assert_type(GB_S.transform("rank"), Series), Series)
check(assert_type(GB_S.transform("shift"), Series), Series)


def test_frame_groupby_agg_reduction_kernels() -> None:
"""Test DataFrameGroupBy.agg with ReductionKernelType literals."""
check(assert_type(GB_DF.agg("all"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("any"), DataFrame), DataFrame)
with pytest_warns_bounded(Pandas4Warning, "corrwith is deprecated", lower="2.99"):
check(assert_type(GB_DF.agg("corrwith", other=DF), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("count"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("first"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("idxmax"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("idxmin"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("last"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("max"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("mean"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("median"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("min"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("nunique"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("prod"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("quantile"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("sem"), DataFrame), DataFrame)
check(assert_type(GB_DF.aggregate("size"), Series), Series)
check(assert_type(GB_DF.agg("skew"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("std"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("sum"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("var"), DataFrame), DataFrame)


def test_frame_groupby_agg_transformation_kernels() -> None:
"""Test DataFrameGroupBy.agg with TransformationKernelType literals."""
check(assert_type(GB_DF.agg("bfill"), DataFrame), DataFrame)
# TODO: pandas-dev/pandas-stubs#1671, cumcount and ngroup return Series at runtime on DataFrameGroupBy
check(assert_type(GB_DF.agg("cummax"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("cummin"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("cumprod"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("cumsum"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("diff"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("ffill"), DataFrame), DataFrame)
# TODO: pandas-dev/pandas-stubs#1671, fillna is not a valid function for DataFrameGroupBy at runtime
check(assert_type(GB_DF.agg("pct_change"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("rank"), DataFrame), DataFrame)
check(assert_type(GB_DF.agg("shift"), DataFrame), DataFrame)


def test_series_groupby_agg_reduction_kernels() -> None:
"""Test SeriesGroupBy.agg with ReductionKernelType literals."""
check(assert_type(GB_S.agg("all"), Series), Series)
check(assert_type(GB_S.agg("any"), Series), Series)
# TODO: pandas-dev/pandas-stubs#1671, corrwith does not exist on SeriesGroupBy
check(assert_type(GB_S.agg("count"), Series), Series)
check(assert_type(GB_S.agg("first"), Series), Series)
check(assert_type(GB_S.agg("idxmax"), Series), Series)
check(assert_type(GB_S.agg("idxmin"), Series), Series)
check(assert_type(GB_S.agg("last"), Series), Series)
check(assert_type(GB_S.agg("max"), Series), Series)
check(assert_type(GB_S.agg("mean"), Series), Series)
check(assert_type(GB_S.agg("median"), Series), Series)
check(assert_type(GB_S.agg("min"), Series), Series)
check(assert_type(GB_S.agg("nunique"), Series), Series)
check(assert_type(GB_S.agg("prod"), Series), Series)
check(assert_type(GB_S.agg("quantile"), Series), Series)
check(assert_type(GB_S.agg("sem"), Series), Series)
check(assert_type(GB_S.agg("size"), Series), Series)
check(assert_type(GB_S.agg("skew"), Series), Series)
check(assert_type(GB_S.agg("std"), Series), Series)
check(assert_type(GB_S.agg("sum"), Series), Series)
check(assert_type(GB_S.agg("var"), Series), Series)


def test_series_groupby_agg_transformation_kernels() -> None:
"""Test SeriesGroupBy.agg with TransformationKernelType literals."""
check(assert_type(GB_S.agg("bfill"), Series), Series)
check(assert_type(GB_S.agg("cumcount"), Series), Series)
check(assert_type(GB_S.agg("cummax"), Series), Series)
check(assert_type(GB_S.agg("cummin"), Series), Series)
check(assert_type(GB_S.agg("cumprod"), Series), Series)
check(assert_type(GB_S.agg("cumsum"), Series), Series)
check(assert_type(GB_S.agg("diff"), Series), Series)
check(assert_type(GB_S.agg("ffill"), Series), Series)
# TODO: pandas-dev/pandas-stubs#1671, fillna does not exist on SeriesGroupBy at runtime
check(assert_type(GB_S.agg("ngroup"), Series), Series)
check(assert_type(GB_S.agg("pct_change"), Series), Series)
check(assert_type(GB_S.agg("rank"), Series), Series)
check(assert_type(GB_S.agg("shift"), Series), Series)