test_frame_apply.py

from datetime import datetime
from itertools import chain
import warnings

import numpy as np
import pytest

from pandas.core.dtypes.dtypes import CategoricalDtype

import pandas as pd
from pandas import (
    DataFrame,
    MultiIndex,
    Series,
    Timestamp,
    date_range,
)
import pandas._testing as tm
from pandas.tests.frame.common import zip_frames


def test_apply(float_frame):
    with np.errstate(all="ignore"):
        # ufunc
        result = np.sqrt(float_frame["A"])
        expected = float_frame.apply(np.sqrt)["A"]
        tm.assert_series_equal(result, expected)

        # aggregator
        result = float_frame.apply(np.mean)["A"]
        expected = np.mean(float_frame["A"])
        assert result == expected

        d = float_frame.index[0]
        result = float_frame.apply(np.mean, axis=1)
        expected = np.mean(float_frame.xs(d))
        assert result[d] == expected
        assert result.index is float_frame.index

    # GH 9573
    df = DataFrame({"c0": ["A", "A", "B", "B"], "c1": ["C", "C", "D", "D"]})
    result = df.apply(lambda ts: ts.astype("category"))

    assert result.shape == (4, 2)
    assert isinstance(result["c0"].dtype, CategoricalDtype)
    assert isinstance(result["c1"].dtype, CategoricalDtype)


def test_apply_axis1_with_ea():
    # GH#36785
    expected = DataFrame({"A": [Timestamp("2013-01-01", tz="UTC")]})
    result = expected.apply(lambda x: x, axis=1)
    tm.assert_frame_equal(result, expected)


def test_apply_mixed_datetimelike():
    # mixed datetimelike
    # GH 7778
    expected = DataFrame(
        {
            "A": date_range("20130101", periods=3),
            "B": pd.to_timedelta(np.arange(3), unit="s"),
        }
    )
    result = expected.apply(lambda x: x, axis=1)
    tm.assert_frame_equal(result, expected)


def test_apply_empty(float_frame):
    # empty
    empty_frame = DataFrame()

    result = empty_frame.apply(np.sqrt)
    assert result.empty

    result = empty_frame.apply(np.mean)
    assert result.empty

    no_rows = float_frame[:0]
    result = no_rows.apply(lambda x: x.mean())
    expected = Series(np.nan, index=float_frame.columns)
    tm.assert_series_equal(result, expected)

    no_cols = float_frame.loc[:, []]
    result = no_cols.apply(lambda x: x.mean(), axis=1)
    expected = Series(np.nan, index=float_frame.index)
    tm.assert_series_equal(result, expected)

    # GH 2476
    expected = DataFrame(index=["a"])
    result = expected.apply(lambda x: x["a"], axis=1)
    tm.assert_frame_equal(result, expected)


def test_apply_with_reduce_empty():
    # reduce with an empty DataFrame
    empty_frame = DataFrame()

    x = []
    result = empty_frame.apply(x.append, axis=1, result_type="expand")
    tm.assert_frame_equal(result, empty_frame)
    result = empty_frame.apply(x.append, axis=1, result_type="reduce")
    expected = Series([], index=pd.Index([], dtype=object), dtype=np.float64)
    tm.assert_series_equal(result, expected)

    empty_with_cols = DataFrame(columns=["a", "b", "c"])
    result = empty_with_cols.apply(x.append, axis=1, result_type="expand")
    tm.assert_frame_equal(result, empty_with_cols)
    result = empty_with_cols.apply(x.append, axis=1, result_type="reduce")
    expected = Series([], index=pd.Index([], dtype=object), dtype=np.float64)
    tm.assert_series_equal(result, expected)

    # Ensure that x.append hasn't been called
    assert x == []


@pytest.mark.parametrize("func", ["sum", "prod", "any", "all"])
def test_apply_funcs_over_empty(func):
    # GH 28213
    df = DataFrame(columns=["a", "b", "c"])

    result = df.apply(getattr(np, func))
    expected = getattr(df, func)()
    tm.assert_series_equal(result, expected)


def test_nunique_empty():
    # GH 28213
    df = DataFrame(columns=["a", "b", "c"])

    result = df.nunique()
    expected = Series(0, index=df.columns)
    tm.assert_series_equal(result, expected)

    result = df.T.nunique()
    expected = Series([], index=pd.Index([]), dtype=np.float64)
    tm.assert_series_equal(result, expected)


def test_apply_standard_nonunique():
    df = DataFrame([[1, 2, 3], [4, 5, 6], [7, 8, 9]], index=["a", "a", "c"])

    result = df.apply(lambda s: s[0], axis=1)
    expected = Series([1, 4, 7], ["a", "a", "c"])
    tm.assert_series_equal(result, expected)

    result = df.T.apply(lambda s: s[0], axis=0)
    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize("func", ["sum", "mean", "min", "max", "std"])
@pytest.mark.parametrize(
    "args,kwds",
    [
        pytest.param([], {}, id="no_args_or_kwds"),
        pytest.param([1], {}, id="axis_from_args"),
        pytest.param([], {"axis": 1}, id="axis_from_kwds"),
        pytest.param([], {"numeric_only": True}, id="optional_kwds"),
        pytest.param([1, None], {"numeric_only": True}, id="args_and_kwds"),
    ],
)
@pytest.mark.parametrize("how", ["agg", "apply"])
def test_apply_with_string_funcs(request, float_frame, func, args, kwds, how):
    if len(args) > 1 and how == "agg":
        request.node.add_marker(
            pytest.mark.xfail(
                raises=TypeError,
                reason="agg/apply signature mismatch - agg passes 2nd "
                "argument to func",
            )
        )
    result = getattr(float_frame, how)(func, *args, **kwds)
    expected = getattr(float_frame, func)(*args, **kwds)
    tm.assert_series_equal(result, expected)


def test_apply_broadcast(float_frame, int_frame_const_col):

    # scalars
    result = float_frame.apply(np.mean, result_type="broadcast")
    expected = DataFrame([float_frame.mean()], index=float_frame.index)
    tm.assert_frame_equal(result, expected)

    result = float_frame.apply(np.mean, axis=1, result_type="broadcast")
    m = float_frame.mean(axis=1)
    expected = DataFrame({c: m for c in float_frame.columns})
    tm.assert_frame_equal(result, expected)

    # lists
    result = float_frame.apply(
        lambda x: list(range(len(float_frame.columns))),
        axis=1,
        result_type="broadcast",
    )
    m = list(range(len(float_frame.columns)))
    expected = DataFrame(
        [m] * len(float_frame.index),
        dtype="float64",
        index=float_frame.index,
        columns=float_frame.columns,
    )
    tm.assert_frame_equal(result, expected)

    result = float_frame.apply(
        lambda x: list(range(len(float_frame.index))), result_type="broadcast"
    )
    m = list(range(len(float_frame.index)))
    expected = DataFrame(
        {c: m for c in float_frame.columns},
        dtype="float64",
        index=float_frame.index,
    )
    tm.assert_frame_equal(result, expected)

    # preserve columns
    df = int_frame_const_col
    result = df.apply(lambda x: [1, 2, 3], axis=1, result_type="broadcast")
    tm.assert_frame_equal(result, df)

    df = int_frame_const_col
    result = df.apply(
        lambda x: Series([1, 2, 3], index=list("abc")),
        axis=1,
        result_type="broadcast",
    )
    expected = df.copy()
    tm.assert_frame_equal(result, expected)


def test_apply_raw(float_frame, mixed_type_frame):
    def _assert_raw(x):
        assert isinstance(x, np.ndarray)
        assert x.ndim == 1

    float_frame.apply(_assert_raw, raw=True)
    float_frame.apply(_assert_raw, axis=1, raw=True)

    result = float_frame.apply(np.mean, raw=True)
    expected = float_frame.apply(lambda x: x.values.mean())
    tm.assert_series_equal(result, expected)

    result = float_frame.apply(np.mean, axis=1, raw=True)
    expected = float_frame.apply(lambda x: x.values.mean(), axis=1)
    tm.assert_series_equal(result, expected)

    # no reduction
    result = float_frame.apply(lambda x: x * 2, raw=True)
    expected = float_frame * 2
    tm.assert_frame_equal(result, expected)

    # Mixed dtype (GH-32423)
    mixed_type_frame.apply(_assert_raw, raw=True)
    mixed_type_frame.apply(_assert_raw, axis=1, raw=True)


def test_apply_axis1(float_frame):
    d = float_frame.index[0]
    result = float_frame.apply(np.mean, axis=1)[d]
    expected = np.mean(float_frame.xs(d))
    assert result == expected


def test_apply_mixed_dtype_corner():
    df = DataFrame({"A": ["foo"], "B": [1.0]})
    result = df[:0].apply(np.mean, axis=1)
    # the result here is actually kind of ambiguous, should it be a Series
    # or a DataFrame?
    expected = Series(np.nan, index=pd.Index([], dtype="int64"))
    tm.assert_series_equal(result, expected)

    df = DataFrame({"A": ["foo"], "B": [1.0]})
    result = df.apply(lambda x: x["A"], axis=1)
    expected = Series(["foo"], index=[0])
    tm.assert_series_equal(result, expected)

    result = df.apply(lambda x: x["B"], axis=1)
    expected = Series([1.0], index=[0])
    tm.assert_series_equal(result, expected)


def test_apply_empty_infer_type():
    no_cols = DataFrame(index=["a", "b", "c"])
    no_index = DataFrame(columns=["a", "b", "c"])

    def _check(df, f):
        with warnings.catch_warnings(record=True):
            warnings.simplefilter("ignore", RuntimeWarning)
            test_res = f(np.array([], dtype="f8"))
        is_reduction = not isinstance(test_res, np.ndarray)

        def _checkit(axis=0, raw=False):
            result = df.apply(f, axis=axis, raw=raw)
            if is_reduction:
                agg_axis = df._get_agg_axis(axis)
                assert isinstance(result, Series)
                assert result.index is agg_axis
            else:
                assert isinstance(result, DataFrame)

        _checkit()
        _checkit(axis=1)
        _checkit(raw=True)
        _checkit(axis=0, raw=True)

    with np.errstate(all="ignore"):
        _check(no_cols, lambda x: x)
        _check(no_cols, lambda x: x.mean())
        _check(no_index, lambda x: x)
        _check(no_index, lambda x: x.mean())

    result = no_cols.apply(lambda x: x.mean(), result_type="broadcast")
    assert isinstance(result, DataFrame)


def test_apply_with_args_kwds(float_frame):
    def add_some(x, howmuch=0):
        return x + howmuch

    def agg_and_add(x, howmuch=0):
        return x.mean() + howmuch

    def subtract_and_divide(x, sub, divide=1):
        return (x - sub) / divide

    result = float_frame.apply(add_some, howmuch=2)
    expected = float_frame.apply(lambda x: x + 2)
    tm.assert_frame_equal(result, expected)

    result = float_frame.apply(agg_and_add, howmuch=2)
    expected = float_frame.apply(lambda x: x.mean() + 2)
    tm.assert_series_equal(result, expected)

    result = float_frame.apply(subtract_and_divide, args=(2,), divide=2)
    expected = float_frame.apply(lambda x: (x - 2.0) / 2.0)
    tm.assert_frame_equal(result, expected)


def test_apply_yield_list(float_frame):
    result = float_frame.apply(list)
    tm.assert_frame_equal(result, float_frame)


def test_apply_reduce_Series(float_frame):
    float_frame["A"].iloc[::2] = np.nan
    expected = float_frame.mean(1)
    result = float_frame.apply(np.mean, axis=1)
    tm.assert_series_equal(result, expected)


def test_apply_reduce_to_dict():
    # GH 25196 37544
    data = DataFrame([[1, 2], [3, 4]], columns=["c0", "c1"], index=["i0", "i1"])

    result = data.apply(dict, axis=0)
    expected = Series([{"i0": 1, "i1": 3}, {"i0": 2, "i1": 4}], index=data.columns)
    tm.assert_series_equal(result, expected)

    result = data.apply(dict, axis=1)
    expected = Series([{"c0": 1, "c1": 2}, {"c0": 3, "c1": 4}], index=data.index)
    tm.assert_series_equal(result, expected)


def test_apply_differently_indexed():
    df = DataFrame(np.random.randn(20, 10))

    result = df.apply(Series.describe, axis=0)
    expected = DataFrame({i: v.describe() for i, v in df.items()}, columns=df.columns)
    tm.assert_frame_equal(result, expected)

    result = df.apply(Series.describe, axis=1)
    expected = DataFrame({i: v.describe() for i, v in df.T.items()}, columns=df.index).T
    tm.assert_frame_equal(result, expected)


def test_apply_bug():

    # GH 6125
    positions = DataFrame(
        [
            [1, "ABC0", 50],
            [1, "YUM0", 20],
            [1, "DEF0", 20],
            [2, "ABC1", 50],
            [2, "YUM1", 20],
            [2, "DEF1", 20],
        ],
        columns=["a", "market", "position"],
    )

    def f(r):
        return r["market"]

    expected = positions.apply(f, axis=1)

    positions = DataFrame(
        [
            [datetime(2013, 1, 1), "ABC0", 50],
            [datetime(2013, 1, 2), "YUM0", 20],
            [datetime(2013, 1, 3), "DEF0", 20],
            [datetime(2013, 1, 4), "ABC1", 50],
            [datetime(2013, 1, 5), "YUM1", 20],
            [datetime(2013, 1, 6), "DEF1", 20],
        ],
        columns=["a", "market", "position"],
    )
    result = positions.apply(f, axis=1)
    tm.assert_series_equal(result, expected)


def test_apply_convert_objects():
    expected = DataFrame(
        {
            "A": [
                "foo",
                "foo",
                "foo",
                "foo",
                "bar",
                "bar",
                "bar",
                "bar",
                "foo",
                "foo",
                "foo",
            ],
            "B": [
                "one",
                "one",
                "one",
                "two",
                "one",
                "one",
                "one",
                "two",
                "two",
                "two",
                "one",
            ],
            "C": [
                "dull",
                "dull",
                "shiny",
                "dull",
                "dull",
                "shiny",
                "shiny",
                "dull",
                "shiny",
                "shiny",
                "shiny",
            ],
            "D": np.random.randn(11),
            "E": np.random.randn(11),
            "F": np.random.randn(11),
        }
    )

    result = expected.apply(lambda x: x, axis=1)._convert(datetime=True)
    tm.assert_frame_equal(result, expected)


def test_apply_attach_name(float_frame):
    result = float_frame.apply(lambda x: x.name)
    expected = Series(float_frame.columns, index=float_frame.columns)
    tm.assert_series_equal(result, expected)

    result = float_frame.apply(lambda x: x.name, axis=1)
    expected = Series(float_frame.index, index=float_frame.index)
    tm.assert_series_equal(result, expected)

    # non-reductions
    result = float_frame.apply(lambda x: np.repeat(x.name, len(x)))
    expected = DataFrame(
        np.tile(float_frame.columns, (len(float_frame.index), 1)),
        index=float_frame.index,
        columns=float_frame.columns,
    )
    tm.assert_frame_equal(result, expected)

    result = float_frame.apply(lambda x: np.repeat(x.name, len(x)), axis=1)
    expected = Series(
        np.repeat(t[0], len(float_frame.columns)) for t in float_frame.itertuples()
    )
    expected.index = float_frame.index
    tm.assert_series_equal(result, expected)


def test_apply_multi_index(float_frame):
    index = MultiIndex.from_arrays([["a", "a", "b"], ["c", "d", "d"]])
    s = DataFrame([[1, 2], [3, 4], [5, 6]], index=index, columns=["col1", "col2"])
    result = s.apply(lambda x: Series({"min": min(x), "max": max(x)}), 1)
    expected = DataFrame([[1, 2], [3, 4], [5, 6]], index=index, columns=["min", "max"])
    tm.assert_frame_equal(result, expected, check_like=True)


def test_apply_dict():

    # GH 8735
    A = DataFrame([["foo", "bar"], ["spam", "eggs"]])
    A_dicts = Series([{0: "foo", 1: "spam"}, {0: "bar", 1: "eggs"}])
    B = DataFrame([[0, 1], [2, 3]])
    B_dicts = Series([{0: 0, 1: 2}, {0: 1, 1: 3}])
    fn = lambda x: x.to_dict()

    for df, dicts in [(A, A_dicts), (B, B_dicts)]:
        reduce_true = df.apply(fn, result_type="reduce")
        reduce_false = df.apply(fn, result_type="expand")
        reduce_none = df.apply(fn)

        tm.assert_series_equal(reduce_true, dicts)
        tm.assert_frame_equal(reduce_false, df)
        tm.assert_series_equal(reduce_none, dicts)


def test_applymap(float_frame):
    applied = float_frame.applymap(lambda x: x * 2)
    tm.assert_frame_equal(applied, float_frame * 2)
    float_frame.applymap(type)

    # GH 465: function returning tuples
    result = float_frame.applymap(lambda x: (x, x))["A"][0]
    assert isinstance(result, tuple)

    # GH 2909: object conversion to float in constructor?
    df = DataFrame(data=[1, "a"])
    result = df.applymap(lambda x: x).dtypes[0]
    assert result == object

    df = DataFrame(data=[1.0, "a"])
    result = df.applymap(lambda x: x).dtypes[0]
    assert result == object

    # GH 2786
    df = DataFrame(np.random.random((3, 4)))
    df2 = df.copy()
    cols = ["a", "a", "a", "a"]
    df.columns = cols

    expected = df2.applymap(str)
    expected.columns = cols
    result = df.applymap(str)
    tm.assert_frame_equal(result, expected)

    # datetime/timedelta
    df["datetime"] = Timestamp("20130101")
    df["timedelta"] = pd.Timedelta("1 min")
    result = df.applymap(str)
    for f in ["datetime", "timedelta"]:
        assert result.loc[0, f] == str(df.loc[0, f])

    # GH 8222
    empty_frames = [
        DataFrame(),
        DataFrame(columns=list("ABC")),
        DataFrame(index=list("ABC")),
        DataFrame({"A": [], "B": [], "C": []}),
    ]
    for expected in empty_frames:
        for func in [round, lambda x: x]:
            result = expected.applymap(func)
            tm.assert_frame_equal(result, expected)


def test_applymap_kwargs():
    # GH 40652
    result = DataFrame([[1, 2], [3, 4]]).applymap(lambda x, y: x + y, y=2)
    expected = DataFrame([[3, 4], [5, 6]])
    tm.assert_frame_equal(result, expected)


def test_applymap_na_ignore(float_frame):
    # GH 23803
    strlen_frame = float_frame.applymap(lambda x: len(str(x)))
    float_frame_with_na = float_frame.copy()
    mask = np.random.randint(0, 2, size=float_frame.shape, dtype=bool)
    float_frame_with_na[mask] = pd.NA
    strlen_frame_na_ignore = float_frame_with_na.applymap(
        lambda x: len(str(x)), na_action="ignore"
    )
    strlen_frame_with_na = strlen_frame.copy()
    strlen_frame_with_na[mask] = pd.NA
    tm.assert_frame_equal(strlen_frame_na_ignore, strlen_frame_with_na)


def test_applymap_box_timestamps():
    # GH 2689, GH 2627
    ser = Series(date_range("1/1/2000", periods=10))

    def func(x):
        return (x.hour, x.day, x.month)

    # it works!
    DataFrame(ser).applymap(func)


def test_applymap_box():
    # ufunc will not be boxed. Same test cases as the test_map_box
    df = DataFrame(
        {
            "a": [Timestamp("2011-01-01"), Timestamp("2011-01-02")],
            "b": [
                Timestamp("2011-01-01", tz="US/Eastern"),
                Timestamp("2011-01-02", tz="US/Eastern"),
            ],
            "c": [pd.Timedelta("1 days"), pd.Timedelta("2 days")],
            "d": [
                pd.Period("2011-01-01", freq="M"),
                pd.Period("2011-01-02", freq="M"),
            ],
        }
    )

    result = df.applymap(lambda x: type(x).__name__)
    expected = DataFrame(
        {
            "a": ["Timestamp", "Timestamp"],
            "b": ["Timestamp", "Timestamp"],
            "c": ["Timedelta", "Timedelta"],
            "d": ["Period", "Period"],
        }
    )
    tm.assert_frame_equal(result, expected)


def test_frame_apply_dont_convert_datetime64():
    from pandas.tseries.offsets import BDay

    df = DataFrame({"x1": [datetime(1996, 1, 1)]})

    df = df.applymap(lambda x: x + BDay())
    df = df.applymap(lambda x: x + BDay())

    result = df.x1.dtype
    assert result == "M8[ns]"


def test_apply_non_numpy_dtype():
    # GH 12244
    df = DataFrame({"dt": date_range("2015-01-01", periods=3, tz="Europe/Brussels")})
    result = df.apply(lambda x: x)
    tm.assert_frame_equal(result, df)

    result = df.apply(lambda x: x + pd.Timedelta("1day"))
    expected = DataFrame(
        {"dt": date_range("2015-01-02", periods=3, tz="Europe/Brussels")}
    )
    tm.assert_frame_equal(result, expected)

    df = DataFrame({"dt": ["a", "b", "c", "a"]}, dtype="category")
    result = df.apply(lambda x: x)
    tm.assert_frame_equal(result, df)


def test_apply_dup_names_multi_agg():
    # GH 21063
    df = DataFrame([[0, 1], [2, 3]], columns=["a", "a"])
    expected = DataFrame([[0, 1]], columns=["a", "a"], index=["min"])
    result = df.agg(["min"])

    tm.assert_frame_equal(result, expected)


def test_apply_nested_result_axis_1():
    # GH 13820
    def apply_list(row):
        return [2 * row["A"], 2 * row["C"], 2 * row["B"]]

    df = DataFrame(np.zeros((4, 4)), columns=list("ABCD"))
    result = df.apply(apply_list, axis=1)
    expected = Series(
        [[0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0]]
    )
    tm.assert_series_equal(result, expected)


def test_apply_noreduction_tzaware_object():
    # https://github.com/pandas-dev/pandas/issues/31505
    expected = DataFrame(
        {"foo": [Timestamp("2020", tz="UTC")]}, dtype="datetime64[ns, UTC]"
    )
    result = expected.apply(lambda x: x)
    tm.assert_frame_equal(result, expected)
    result = expected.apply(lambda x: x.copy())
    tm.assert_frame_equal(result, expected)


def test_apply_function_runs_once():
    # https://github.com/pandas-dev/pandas/issues/30815

    df = DataFrame({"a": [1, 2, 3]})
    names = []  # Save row names function is applied to

    def reducing_function(row):
        names.append(row.name)

    def non_reducing_function(row):
        names.append(row.name)
        return row

    for func in [reducing_function, non_reducing_function]:
        del names[:]

        df.apply(func, axis=1)
        assert names == list(df.index)


def test_apply_raw_function_runs_once():
    # https://github.com/pandas-dev/pandas/issues/34506

    df = DataFrame({"a": [1, 2, 3]})
    values = []  # Save row values function is applied to

    def reducing_function(row):
        values.extend(row)

    def non_reducing_function(row):
        values.extend(row)
        return row

    for func in [reducing_function, non_reducing_function]:
        del values[:]

        df.apply(func, raw=True, axis=1)
        assert values == list(df.a.to_list())


def test_applymap_function_runs_once():

    df = DataFrame({"a": [1, 2, 3]})
    values = []  # Save values function is applied to

    def reducing_function(val):
        values.append(val)

    def non_reducing_function(val):
        values.append(val)
        return val

    for func in [reducing_function, non_reducing_function]:
        del values[:]

        df.applymap(func)
        assert values == df.a.to_list()


def test_apply_with_byte_string():
    # GH 34529
    df = DataFrame(np.array([b"abcd", b"efgh"]), columns=["col"])
    expected = DataFrame(np.array([b"abcd", b"efgh"]), columns=["col"], dtype=object)
    # After we make the aply we exect a dataframe just
    # like the original but with the object datatype
    result = df.apply(lambda x: x.astype("object"))
    tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize("val", ["asd", 12, None, np.NaN])
def test_apply_category_equalness(val):
    # Check if categorical comparisons on apply, GH 21239
    df_values = ["asd", None, 12, "asd", "cde", np.NaN]
    df = DataFrame({"a": df_values}, dtype="category")

    result = df.a.apply(lambda x: x == val)
    expected = Series(
        [np.NaN if pd.isnull(x) else x == val for x in df_values], name="a"
    )
    tm.assert_series_equal(result, expected)


# the user has supplied an opaque UDF where
# they are transforming the input that requires
# us to infer the output


def test_infer_row_shape():
    # GH 17437
    # if row shape is changing, infer it
    df = DataFrame(np.random.rand(10, 2))
    result = df.apply(np.fft.fft, axis=0).shape
    assert result == (10, 2)

    result = df.apply(np.fft.rfft, axis=0).shape
    assert result == (6, 2)


def test_with_dictlike_columns():
    # GH 17602
    df = DataFrame([[1, 2], [1, 2]], columns=["a", "b"])
    result = df.apply(lambda x: {"s": x["a"] + x["b"]}, axis=1)
    expected = Series([{"s": 3} for t in df.itertuples()])
    tm.assert_series_equal(result, expected)

    df["tm"] = [
        Timestamp("2017-05-01 00:00:00"),
        Timestamp("2017-05-02 00:00:00"),
    ]
    result = df.apply(lambda x: {"s": x["a"] + x["b"]}, axis=1)
    tm.assert_series_equal(result, expected)

    # compose a series
    result = (df["a"] + df["b"]).apply(lambda x: {"s": x})
    expected = Series([{"s": 3}, {"s": 3}])
    tm.assert_series_equal(result, expected)

    # GH 18775
    df = DataFrame()
    df["author"] = ["X", "Y", "Z"]
    df["publisher"] = ["BBC", "NBC", "N24"]
    df["date"] = pd.to_datetime(
        ["17-10-2010 07:15:30", "13-05-2011 08:20:35", "15-01-2013 09:09:09"]
    )
    result = df.apply(lambda x: {}, axis=1)
    expected = Series([{}, {}, {}])
    tm.assert_series_equal(result, expected)


def test_with_dictlike_columns_with_infer():
    # GH 17602
    df = DataFrame([[1, 2], [1, 2]], columns=["a", "b"])
    result = df.apply(lambda x: {"s": x["a"] + x["b"]}, axis=1, result_type="expand")
    expected = DataFrame({"s": [3, 3]})
    tm.assert_frame_equal(result, expected)

    df["tm"] = [
        Timestamp("2017-05-01 00:00:00"),
        Timestamp("2017-05-02 00:00:00"),
    ]
    result = df.apply(lambda x: {"s": x["a"] + x["b"]}, axis=1, result_type="expand")
    tm.assert_frame_equal(result, expected)


def test_with_listlike_columns():
    # GH 17348
    df = DataFrame(
        {
            "a": Series(np.random.randn(4)),
            "b": ["a", "list", "of", "words"],
            "ts": date_range("2016-10-01", periods=4, freq="H"),
        }
    )

    result = df[["a", "b"]].apply(tuple, axis=1)
    expected = Series([t[1:] for t in df[["a", "b"]].itertuples()])
    tm.assert_series_equal(result, expected)

    result = df[["a", "ts"]].apply(tuple, axis=1)
    expected = Series([t[1:] for t in df[["a", "ts"]].itertuples()])
    tm.assert_series_equal(result, expected)

    # GH 18919
    df = DataFrame({"x": Series([["a", "b"], ["q"]]), "y": Series([["z"], ["q", "t"]])})
    df.index = MultiIndex.from_tuples([("i0", "j0"), ("i1", "j1")])

    result = df.apply(lambda row: [el for el in row["x"] if el in row["y"]], axis=1)
    expected = Series([[], ["q"]], index=df.index)
    tm.assert_series_equal(result, expected)


def test_infer_output_shape_columns():
    # GH 18573

    df = DataFrame(
        {
            "number": [1.0, 2.0],
            "string": ["foo", "bar"],
            "datetime": [
                Timestamp("2017-11-29 03:30:00"),
                Timestamp("2017-11-29 03:45:00"),
            ],
        }
    )
    result = df.apply(lambda row: (row.number, row.string), axis=1)
    expected = Series([(t.number, t.string) for t in df.itertuples()])
    tm.assert_series_equal(result, expected)


def test_infer_output_shape_listlike_columns():
    # GH 16353

    df = DataFrame(np.random.randn(6, 3), columns=["A", "B", "C"])

    result = df.apply(lambda x: [1, 2, 3], axis=1)
    expected = Series([[1, 2, 3] for t in df.itertuples()])
    tm.assert_series_equal(result, expected)

    result = df.apply(lambda x: [1, 2], axis=1)
    expected = Series([[1, 2] for t in df.itertuples()])
    tm.assert_series_equal(result, expected)

    # GH 17970
    df = DataFrame({"a": [1, 2, 3]}, index=list("abc"))

    result = df.apply(lambda row: np.ones(1), axis=1)
    expected = Series([np.ones(1) for t in df.itertuples()], index=df.index)
    tm.assert_series_equal(result, expected)

    result = df.apply(lambda row: np.ones(2), axis=1)
    expected = Series([np.ones(2) for t in df.itertuples()], index=df.index)
    tm.assert_series_equal(result, expected)

    # GH 17892
    df = DataFrame(
        {
            "a": [
                Timestamp("2010-02-01"),
                Timestamp("2010-02-04"),
                Timestamp("2010-02-05"),
                Timestamp("2010-02-06"),
            ],
            "b": [9, 5, 4, 3],
            "c": [5, 3, 4, 2],
            "d": [1, 2, 3, 4],
        }
    )

    def fun(x):
        return (1, 2)

    result = df.apply(fun, axis=1)
    expected = Series([(1, 2) for t in df.itertuples()])
    tm.assert_series_equal(result, expected)


def test_consistent_coerce_for_shapes():
    # we want column names to NOT be propagated
    # just because the shape matches the input shape
    df = DataFrame(np.random.randn(4, 3), columns=["A", "B", "C"])

    result = df.apply(lambda x: [1, 2, 3], axis=1)
    expected = Series([[1, 2, 3] for t in df.itertuples()])
    tm.assert_series_equal(result, expected)

    result = df.apply(lambda x: [1, 2], axis=1)
    expected = Series([[1, 2] for t in df.itertuples()])
    tm.assert_series_equal(result, expected)


def test_consistent_names(int_frame_const_col):
    # if a Series is returned, we should use the resulting index names
    df = int_frame_const_col

    result = df.apply(
        lambda x: Series([1, 2, 3], index=["test", "other", "cols"]), axis=1
    )
    expected = int_frame_const_col.rename(
        columns={"A": "test", "B": "other", "C": "cols"}
    )
    tm.assert_frame_equal(result, expected)

    result = df.apply(lambda x: Series([1, 2], index=["test", "other"]), axis=1)
    expected = expected[["test", "other"]]
    tm.assert_frame_equal(result, expected)


def test_result_type(int_frame_const_col):
    # result_type should be consistent no matter which
    # path we take in the code
    df = int_frame_const_col

    result = df.apply(lambda x: [1, 2, 3], axis=1, result_type="expand")
    expected = df.copy()
    expected.columns = [0, 1, 2]
    tm.assert_frame_equal(result, expected)

    result = df.apply(lambda x: [1, 2], axis=1, result_type="expand")
    expected = df[["A", "B"]].copy()
    expected.columns = [0, 1]
    tm.assert_frame_equal(result, expected)

    # broadcast result
    result = df.apply(lambda x: [1, 2, 3], axis=1, result_type="broadcast")
    expected = df.copy()
    tm.assert_frame_equal(result, expected)

    columns = ["other", "col", "names"]
    result = df.apply(
        lambda x: Series([1, 2, 3], index=columns), axis=1, result_type="broadcast"
    )
    expected = df.copy()
    tm.assert_frame_equal(result, expected)

    # series result
    result = df.apply(lambda x: Series([1, 2, 3], index=x.index), axis=1)
    expected = df.copy()
    tm.assert_frame_equal(result, expected)

    # series result with other index
    columns = ["other", "col", "names"]
    result = df.apply(lambda x: Series([1, 2, 3], index=columns), axis=1)
    expected = df.copy()
    expected.columns = columns
    tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize(
    "box",
    [lambda x: list(x), lambda x: tuple(x), lambda x: np.array(x, dtype="int64")],
    ids=["list", "tuple", "array"],
)
def test_consistency_for_boxed(box, int_frame_const_col):
    # passing an array or list should not affect the output shape
    df = int_frame_const_col

    result = df.apply(lambda x: box([1, 2]), axis=1)
    expected = Series([box([1, 2]) for t in df.itertuples()])
    tm.assert_series_equal(result, expected)

    result = df.apply(lambda x: box([1, 2]), axis=1, result_type="expand")
    expected = int_frame_const_col[["A", "B"]].rename(columns={"A": 0, "B": 1})
    tm.assert_frame_equal(result, expected)


def test_agg_transform(axis, float_frame):
    other_axis = 1 if axis in {0, "index"} else 0

    with np.errstate(all="ignore"):

        f_abs = np.abs(float_frame)
        f_sqrt = np.sqrt(float_frame)

        # ufunc
        expected = f_sqrt.copy()
        result = float_frame.apply(np.sqrt, axis=axis)
        tm.assert_frame_equal(result, expected)

        # list-like
        result = float_frame.apply([np.sqrt], axis=axis)
        expected = f_sqrt.copy()
        if axis in {0, "index"}:
            expected.columns = MultiIndex.from_product([float_frame.columns, ["sqrt"]])
        else:
            expected.index = MultiIndex.from_product([float_frame.index, ["sqrt"]])
        tm.assert_frame_equal(result, expected)

        # multiple items in list
        # these are in the order as if we are applying both
        # functions per series and then concatting
        result = float_frame.apply([np.abs, np.sqrt], axis=axis)
        expected = zip_frames([f_abs, f_sqrt], axis=other_axis)
        if axis in {0, "index"}:
            expected.columns = MultiIndex.from_product(
                [float_frame.columns, ["absolute", "sqrt"]]
            )
        else:
            expected.index = MultiIndex.from_product(
                [float_frame.index, ["absolute", "sqrt"]]
            )
        tm.assert_frame_equal(result, expected)


def test_demo():
    # demonstration tests
    df = DataFrame({"A": range(5), "B": 5})

    result = df.agg(["min", "max"])
    expected = DataFrame(
        {"A": [0, 4], "B": [5, 5]}, columns=["A", "B"], index=["min", "max"]
    )
    tm.assert_frame_equal(result, expected)

    result = df.agg({"A": ["min", "max"], "B": ["sum", "max"]})
    expected = DataFrame(
        {"A": [4.0, 0.0, np.nan], "B": [5.0, np.nan, 25.0]},
        columns=["A", "B"],
        index=["max", "min", "sum"],
    )
    tm.assert_frame_equal(result.reindex_like(expected), expected)


def test_agg_with_name_as_column_name():
    # GH 36212 - Column name is "name"
    data = {"name": ["foo", "bar"]}
    df = DataFrame(data)

    # result's name should be None
    result = df.agg({"name": "count"})
    expected = Series({"name": 2})
    tm.assert_series_equal(result, expected)

    # Check if name is still preserved when aggregating series instead
    result = df["name"].agg({"name": "count"})
    expected = Series({"name": 2}, name="name")
    tm.assert_series_equal(result, expected)


def test_agg_multiple_mixed_no_warning():
    # GH 20909
    mdf = DataFrame(
        {
            "A": [1, 2, 3],
            "B": [1.0, 2.0, 3.0],
            "C": ["foo", "bar", "baz"],
            "D": date_range("20130101", periods=3),
        }
    )
    expected = DataFrame(
        {
            "A": [1, 6],
            "B": [1.0, 6.0],
            "C": ["bar", "foobarbaz"],
            "D": [Timestamp("2013-01-01"), pd.NaT],
        },
        index=["min", "sum"],
    )
    # sorted index
    with tm.assert_produces_warning(None):
        result = mdf.agg(["min", "sum"])

    tm.assert_frame_equal(result, expected)

    with tm.assert_produces_warning(None):
        result = mdf[["D", "C", "B", "A"]].agg(["sum", "min"])

    # GH40420: the result of .agg should have an index that is sorted
    # according to the arguments provided to agg.
    expected = expected[["D", "C", "B", "A"]].reindex(["sum", "min"])
    tm.assert_frame_equal(result, expected)


def test_agg_reduce(axis, float_frame):
    other_axis = 1 if axis in {0, "index"} else 0
    name1, name2 = float_frame.axes[other_axis].unique()[:2].sort_values()

    # all reducers
    expected = pd.concat(
        [
            float_frame.mean(axis=axis),
            float_frame.max(axis=axis),
            float_frame.sum(axis=axis),
        ],
        axis=1,
    )
    expected.columns = ["mean", "max", "sum"]
    expected = expected.T if axis in {0, "index"} else expected

    result = float_frame.agg(["mean", "max", "sum"], axis=axis)
    tm.assert_frame_equal(result, expected)

    # dict input with scalars
    func = {name1: "mean", name2: "sum"}
    result = float_frame.agg(func, axis=axis)
    expected = Series(
        [
            float_frame.loc(other_axis)[name1].mean(),
            float_frame.loc(other_axis)[name2].sum(),
        ],
        index=[name1, name2],
    )
    tm.assert_series_equal(result, expected)

    # dict input with lists
    func = {name1: ["mean"], name2: ["sum"]}
    result = float_frame.agg(func, axis=axis)
    expected = DataFrame(
        {
            name1: Series([float_frame.loc(other_axis)[name1].mean()], index=["mean"]),
            name2: Series([float_frame.loc(other_axis)[name2].sum()], index=["sum"]),
        }
    )
    expected = expected.T if axis in {1, "columns"} else expected
    tm.assert_frame_equal(result, expected)

    # dict input with lists with multiple
    func = {name1: ["mean", "sum"], name2: ["sum", "max"]}
    result = float_frame.agg(func, axis=axis)
    expected = pd.concat(
        {
            name1: Series(
                [
                    float_frame.loc(other_axis)[name1].mean(),
                    float_frame.loc(other_axis)[name1].sum(),
                ],
                index=["mean", "sum"],
            ),
            name2: Series(
                [
                    float_frame.loc(other_axis)[name2].sum(),
                    float_frame.loc(other_axis)[name2].max(),
                ],
                index=["sum", "max"],
            ),
        },
        axis=1,
    )
    expected = expected.T if axis in {1, "columns"} else expected
    tm.assert_frame_equal(result, expected)


def test_nuiscance_columns():

    # GH 15015
    df = DataFrame(
        {
            "A": [1, 2, 3],
            "B": [1.0, 2.0, 3.0],
            "C": ["foo", "bar", "baz"],
            "D": date_range("20130101", periods=3),
        }
    )

    result = df.agg("min")
    expected = Series([1, 1.0, "bar", Timestamp("20130101")], index=df.columns)
    tm.assert_series_equal(result, expected)

    result = df.agg(["min"])
    expected = DataFrame(
        [[1, 1.0, "bar", Timestamp("20130101")]],
        index=["min"],
        columns=df.columns,
    )
    tm.assert_frame_equal(result, expected)

    with tm.assert_produces_warning(
        FutureWarning, match="Select only valid", check_stacklevel=False
    ):
        result = df.agg("sum")
    expected = Series([6, 6.0, "foobarbaz"], index=["A", "B", "C"])
    tm.assert_series_equal(result, expected)

    result = df.agg(["sum"])
    expected = DataFrame(
        [[6, 6.0, "foobarbaz"]], index=["sum"], columns=["A", "B", "C"]
    )
    tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize("how", ["agg", "apply"])
def test_non_callable_aggregates(how):

    # GH 16405
    # 'size' is a property of frame/series
    # validate that this is working
    # GH 39116 - expand to apply
    df = DataFrame(
        {"A": [None, 2, 3], "B": [1.0, np.nan, 3.0], "C": ["foo", None, "bar"]}
    )

    # Function aggregate
    result = getattr(df, how)({"A": "count"})
    expected = Series({"A": 2})

    tm.assert_series_equal(result, expected)

    # Non-function aggregate
    result = getattr(df, how)({"A": "size"})
    expected = Series({"A": 3})

    tm.assert_series_equal(result, expected)

    # Mix function and non-function aggs
    result1 = getattr(df, how)(["count", "size"])
    result2 = getattr(df, how)(
        {"A": ["count", "size"], "B": ["count", "size"], "C": ["count", "size"]}
    )
    expected = DataFrame(
        {
            "A": {"count": 2, "size": 3},
            "B": {"count": 2, "size": 3},
            "C": {"count": 2, "size": 3},
        }
    )

    tm.assert_frame_equal(result1, result2, check_like=True)
    tm.assert_frame_equal(result2, expected, check_like=True)

    # Just functional string arg is same as calling df.arg()
    result = getattr(df, how)("count")
    expected = df.count()

    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize("how", ["agg", "apply"])
def test_size_as_str(how, axis):
    # GH 39934
    df = DataFrame(
        {"A": [None, 2, 3], "B": [1.0, np.nan, 3.0], "C": ["foo", None, "bar"]}
    )
    # Just a string attribute arg same as calling df.arg
    # on the columns
    result = getattr(df, how)("size", axis=axis)
    if axis == 0 or axis == "index":
        expected = Series(df.shape[0], index=df.columns, name="size")
    else:
        expected = Series(df.shape[1], index=df.index, name="size")
    tm.assert_series_equal(result, expected)


def test_agg_listlike_result():
    # GH-29587 user defined function returning list-likes
    df = DataFrame({"A": [2, 2, 3], "B": [1.5, np.nan, 1.5], "C": ["foo", None, "bar"]})

    def func(group_col):
        return list(group_col.dropna().unique())

    result = df.agg(func)
    expected = Series([[2, 3], [1.5], ["foo", "bar"]], index=["A", "B", "C"])
    tm.assert_series_equal(result, expected)

    result = df.agg([func])
    expected = expected.to_frame("func").T
    tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize(
    "df, func, expected",
    chain(
        tm.get_cython_table_params(
            DataFrame(),
            [
                ("sum", Series(dtype="float64")),
                ("max", Series(dtype="float64")),
                ("min", Series(dtype="float64")),
                ("all", Series(dtype=bool)),
                ("any", Series(dtype=bool)),
                ("mean", Series(dtype="float64")),
                ("prod", Series(dtype="float64")),
                ("std", Series(dtype="float64")),
                ("var", Series(dtype="float64")),
                ("median", Series(dtype="float64")),
            ],
        ),
        tm.get_cython_table_params(
            DataFrame([[np.nan, 1], [1, 2]]),
            [
                ("sum", Series([1.0, 3])),
                ("max", Series([1.0, 2])),
                ("min", Series([1.0, 1])),
                ("all", Series([True, True])),
                ("any", Series([True, True])),
                ("mean", Series([1, 1.5])),
                ("prod", Series([1.0, 2])),
                ("std", Series([np.nan, 0.707107])),
                ("var", Series([np.nan, 0.5])),
                ("median", Series([1, 1.5])),
            ],
        ),
    ),
)
def test_agg_cython_table(df, func, expected, axis):
    # GH 21224
    # test reducing functions in
    # pandas.core.base.SelectionMixin._cython_table
    result = df.agg(func, axis=axis)
    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize(
    "df, func, expected",
    chain(
        tm.get_cython_table_params(
            DataFrame(), [("cumprod", DataFrame()), ("cumsum", DataFrame())]
        ),
        tm.get_cython_table_params(
            DataFrame([[np.nan, 1], [1, 2]]),
            [
                ("cumprod", DataFrame([[np.nan, 1], [1, 2]])),
                ("cumsum", DataFrame([[np.nan, 1], [1, 3]])),
            ],
        ),
    ),
)
def test_agg_cython_table_transform(df, func, expected, axis):
    # GH 21224
    # test transforming functions in
    # pandas.core.base.SelectionMixin._cython_table (cumprod, cumsum)
    if axis == "columns" or axis == 1:
        # operating blockwise doesn't let us preserve dtypes
        expected = expected.astype("float64")

    result = df.agg(func, axis=axis)
    tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize("axis", [0, 1])
@pytest.mark.parametrize(
    "args, kwargs",
    [
        ((1, 2, 3), {}),
        ((8, 7, 15), {}),
        ((1, 2), {}),
        ((1,), {"b": 2}),
        ((), {"a": 1, "b": 2}),
        ((), {"a": 2, "b": 1}),
        ((), {"a": 1, "b": 2, "c": 3}),
    ],
)
def test_agg_args_kwargs(axis, args, kwargs):
    def f(x, a, b, c=3):
        return x.sum() + (a + b) / c

    df = DataFrame([[1, 2], [3, 4]])

    if axis == 0:
        expected = Series([5.0, 7.0])
    else:
        expected = Series([4.0, 8.0])

    result = df.agg(f, axis, *args, **kwargs)

    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize("num_cols", [2, 3, 5])
def test_frequency_is_original(num_cols):
    # GH 22150
    index = pd.DatetimeIndex(["1950-06-30", "1952-10-24", "1953-05-29"])
    original = index.copy()
    df = DataFrame(1, index=index, columns=range(num_cols))
    df.apply(lambda x: x)
    assert index.freq == original.freq


def test_apply_datetime_tz_issue():
    # GH 29052

    timestamps = [
        Timestamp("2019-03-15 12:34:31.909000+0000", tz="UTC"),
        Timestamp("2019-03-15 12:34:34.359000+0000", tz="UTC"),
        Timestamp("2019-03-15 12:34:34.660000+0000", tz="UTC"),
    ]
    df = DataFrame(data=[0, 1, 2], index=timestamps)
    result = df.apply(lambda x: x.name, axis=1)
    expected = Series(index=timestamps, data=timestamps)

    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize("df", [DataFrame({"A": ["a", None], "B": ["c", "d"]})])
@pytest.mark.parametrize("method", ["min", "max", "sum"])
def test_consistency_of_aggregates_of_columns_with_missing_values(df, method):
    # GH 16832
    with tm.assert_produces_warning(FutureWarning, match="Select only valid"):
        none_in_first_column_result = getattr(df[["A", "B"]], method)()
        none_in_second_column_result = getattr(df[["B", "A"]], method)()

    tm.assert_series_equal(none_in_first_column_result, none_in_second_column_result)


@pytest.mark.parametrize("col", [1, 1.0, True, "a", np.nan])
def test_apply_dtype(col):
    # GH 31466
    df = DataFrame([[1.0, col]], columns=["a", "b"])
    result = df.apply(lambda x: x.dtype)
    expected = df.dtypes

    tm.assert_series_equal(result, expected)


def test_apply_mutating(using_array_manager):
    # GH#35462 case where applied func pins a new BlockManager to a row
    df = DataFrame({"a": range(100), "b": range(100, 200)})
    df_orig = df.copy()

    def func(row):
        mgr = row._mgr
        row.loc["a"] += 1
        assert row._mgr is not mgr
        return row

    expected = df.copy()
    expected["a"] += 1

    result = df.apply(func, axis=1)

    tm.assert_frame_equal(result, expected)
    if not using_array_manager:
        # INFO(ArrayManager) With BlockManager, the row is a view and mutated in place,
        # with ArrayManager the row is not a view, and thus not mutated in place
        tm.assert_frame_equal(df, result)
    else:
        tm.assert_frame_equal(df, df_orig)


def test_apply_empty_list_reduce():
    # GH#35683 get columns correct
    df = DataFrame([[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]], columns=["a", "b"])

    result = df.apply(lambda x: [], result_type="reduce")
    expected = Series({"a": [], "b": []}, dtype=object)
    tm.assert_series_equal(result, expected)


def test_apply_no_suffix_index():
    # GH36189
    pdf = DataFrame([[4, 9]] * 3, columns=["A", "B"])
    result = pdf.apply(["sum", lambda x: x.sum(), lambda x: x.sum()])
    expected = DataFrame(
        {"A": [12, 12, 12], "B": [27, 27, 27]}, index=["sum", "<lambda>", "<lambda>"]
    )

    tm.assert_frame_equal(result, expected)


def test_apply_raw_returns_string():
    # https://github.com/pandas-dev/pandas/issues/35940
    df = DataFrame({"A": ["aa", "bbb"]})
    result = df.apply(lambda x: x[0], axis=1, raw=True)
    expected = Series(["aa", "bbb"])
    tm.assert_series_equal(result, expected)


@pytest.mark.parametrize(
    "op", ["abs", "ceil", "cos", "cumsum", "exp", "log", "sqrt", "square"]
)
@pytest.mark.parametrize("how", ["transform", "apply"])
def test_apply_np_transformer(float_frame, op, how):
    # GH 39116
    result = getattr(float_frame, how)(op)
    expected = getattr(np, op)(float_frame)
    tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize("op", ["mean", "median", "std", "var"])
@pytest.mark.parametrize("how", ["agg", "apply"])
def test_apply_np_reducer(float_frame, op, how):
    # GH 39116
    float_frame = DataFrame({"a": [1, 2], "b": [3, 4]})
    result = getattr(float_frame, how)(op)
    # pandas ddof defaults to 1, numpy to 0
    kwargs = {"ddof": 1} if op in ("std", "var") else {}
    expected = Series(
        getattr(np, op)(float_frame, axis=0, **kwargs), index=float_frame.columns
    )
    tm.assert_series_equal(result, expected)


def test_aggregation_func_column_order():
    # GH40420: the result of .agg should have an index that is sorted
    # according to the arguments provided to agg.
    df = DataFrame(
        [
            ("1", 1, 0, 0),
            ("2", 2, 0, 0),
            ("3", 3, 0, 0),
            ("4", 4, 5, 4),
            ("5", 5, 6, 6),
            ("6", 6, 7, 7),
        ],
        columns=("item", "att1", "att2", "att3"),
    )

    def foo(s):
        return s.sum() / 2

    aggs = ["sum", foo, "count", "min"]
    result = df.agg(aggs)
    expected = DataFrame(
        {
            "item": ["123456", np.nan, 6, "1"],
            "att1": [21.0, 10.5, 6.0, 1.0],
            "att2": [18.0, 9.0, 6.0, 0.0],
            "att3": [17.0, 8.5, 6.0, 0.0],
        },
        index=["sum", "foo", "count", "min"],
    )
    tm.assert_frame_equal(result, expected)


def test_apply_getitem_axis_1():
    # GH 13427
    df = DataFrame({"a": [0, 1, 2], "b": [1, 2, 3]})
    result = df[["a", "a"]].apply(lambda x: x[0] + x[1], axis=1)
    expected = Series([0, 2, 4])
    tm.assert_series_equal(result, expected)