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REGR: DataFrame reduction with min_count #41711

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Jun 1, 2021
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.2.5.rst
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ including other versions of pandas.
Fixed regressions
~~~~~~~~~~~~~~~~~
- Regression in :func:`concat` between two :class:`DataFrames` where one has an :class:`Index` that is all-None and the other is :class:`DatetimeIndex` incorrectly raising (:issue:`40841`)
- Fixed regression in :meth:`DataFrame.sum` and :meth:`DataFrame.prod` when ``min_count`` and ``numeric_only`` are both given (:issue:`41074`)
- Regression in :func:`read_csv` when using ``memory_map=True`` with an non-UTF8 encoding (:issue:`40986`)
-

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3 changes: 1 addition & 2 deletions pandas/core/frame.py
Original file line number Diff line number Diff line change
Expand Up @@ -9775,7 +9775,6 @@ def _reduce(
**kwds,
):

min_count = kwds.get("min_count", 0)
assert filter_type is None or filter_type == "bool", filter_type
out_dtype = "bool" if filter_type == "bool" else None

Expand Down Expand Up @@ -9824,7 +9823,7 @@ def _get_data() -> DataFrame:
data = self._get_bool_data()
return data

if (numeric_only is not None or axis == 0) and min_count == 0:
if numeric_only is not None or axis == 0:
# For numeric_only non-None and axis non-None, we know
# which blocks to use and no try/except is needed.
# For numeric_only=None only the case with axis==0 and no object
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2 changes: 1 addition & 1 deletion pandas/core/internals/blocks.py
Original file line number Diff line number Diff line change
Expand Up @@ -393,7 +393,7 @@ def reduce(self, func, ignore_failures: bool = False) -> list[Block]:
return []
raise

if np.ndim(result) == 0:
if self.values.ndim == 1:
# TODO(EA2D): special case not needed with 2D EAs
res_values = np.array([[result]])
else:
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3 changes: 1 addition & 2 deletions pandas/core/nanops.py
Original file line number Diff line number Diff line change
Expand Up @@ -245,8 +245,7 @@ def _maybe_get_mask(
"""
if mask is None:
if is_bool_dtype(values.dtype) or is_integer_dtype(values.dtype):
# Boolean data cannot contain nulls, so signal via mask being None
return None
return np.broadcast_to(False, values.shape)
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@jorisvandenbossche jorisvandenbossche Jun 8, 2021

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@jbrockmendel didn't check the rest of the PR, but was this change a crucial part of the fix?

There are bunch of benchmarks showing a slowdown (almost all Ops benchmarks involving integer and boolean data), so that might be caused by this (didn't check to be sure).

See https://pandas.pydata.org/speed/pandas/#regressions?sort=1&dir=desc, scroll a bit down until "2021-06-02 00:29"

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but was this change a crucial part of the fix?

yes

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The reason this seemed necessary was because _maybe_null_out was returning a wrong shape when the mask was None -> #41920


if skipna or needs_i8_conversion(values.dtype):
mask = isna(values)
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31 changes: 23 additions & 8 deletions pandas/tests/frame/test_reductions.py
Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
from datetime import timedelta
from decimal import Decimal
import re

from dateutil.tz import tzlocal
import numpy as np
Expand Down Expand Up @@ -811,35 +812,36 @@ def test_sum_corner(self):
assert len(axis1) == 0

@pytest.mark.parametrize("method, unit", [("sum", 0), ("prod", 1)])
def test_sum_prod_nanops(self, method, unit):
@pytest.mark.parametrize("numeric_only", [None, True, False])
def test_sum_prod_nanops(self, method, unit, numeric_only):
idx = ["a", "b", "c"]
df = DataFrame({"a": [unit, unit], "b": [unit, np.nan], "c": [np.nan, np.nan]})
# The default
result = getattr(df, method)()
result = getattr(df, method)(numeric_only=numeric_only)
expected = Series([unit, unit, unit], index=idx, dtype="float64")
tm.assert_series_equal(result, expected)

# min_count=1
result = getattr(df, method)(min_count=1)
result = getattr(df, method)(numeric_only=numeric_only, min_count=1)
expected = Series([unit, unit, np.nan], index=idx)
tm.assert_series_equal(result, expected)

# min_count=0
result = getattr(df, method)(min_count=0)
result = getattr(df, method)(numeric_only=numeric_only, min_count=0)
expected = Series([unit, unit, unit], index=idx, dtype="float64")
tm.assert_series_equal(result, expected)

result = getattr(df.iloc[1:], method)(min_count=1)
result = getattr(df.iloc[1:], method)(numeric_only=numeric_only, min_count=1)
expected = Series([unit, np.nan, np.nan], index=idx)
tm.assert_series_equal(result, expected)

# min_count > 1
df = DataFrame({"A": [unit] * 10, "B": [unit] * 5 + [np.nan] * 5})
result = getattr(df, method)(min_count=5)
result = getattr(df, method)(numeric_only=numeric_only, min_count=5)
expected = Series(result, index=["A", "B"])
tm.assert_series_equal(result, expected)

result = getattr(df, method)(min_count=6)
result = getattr(df, method)(numeric_only=numeric_only, min_count=6)
expected = Series(result, index=["A", "B"])
tm.assert_series_equal(result, expected)

Expand Down Expand Up @@ -1685,7 +1687,7 @@ def test_minmax_extensionarray(method, numeric_only):


@pytest.mark.parametrize("meth", ["max", "min", "sum", "mean", "median"])
def test_groupy_regular_arithmetic_equivalent(meth):
def test_groupby_regular_arithmetic_equivalent(meth):
# GH#40660
df = DataFrame(
{"a": [pd.Timedelta(hours=6), pd.Timedelta(hours=7)], "b": [12.1, 13.3]}
Expand All @@ -1708,3 +1710,16 @@ def test_frame_mixed_numeric_object_with_timestamp(ts_value):
result = df.sum()
expected = Series([1, 1.1, "foo"], index=list("abc"))
tm.assert_series_equal(result, expected)


def test_prod_sum_min_count_mixed_object():
# https://github.com/pandas-dev/pandas/issues/41074
df = DataFrame([1, "a", True])

result = df.prod(axis=0, min_count=1, numeric_only=False)
expected = Series(["a"])
tm.assert_series_equal(result, expected)

msg = re.escape("unsupported operand type(s) for +: 'int' and 'str'")
with pytest.raises(TypeError, match=msg):
df.sum(axis=0, min_count=1, numeric_only=False)