first commit

.venv/Lib/site-packages/pandas/tests/apply/common.py

@@ -0,0 +1,10 @@
+from pandas.core.groupby.base import transformation_kernels
+
+# tshift only works on time index and is deprecated
+# There is no Series.cumcount or DataFrame.cumcount
+series_transform_kernels = [
+    x for x in sorted(transformation_kernels) if x not in ["tshift", "cumcount"]
+]
+frame_transform_kernels = [
+    x for x in sorted(transformation_kernels) if x not in ["tshift", "cumcount"]
+]

.venv/Lib/site-packages/pandas/tests/apply/conftest.py

@@ -0,0 +1,18 @@
+import numpy as np
+import pytest
+
+from pandas import DataFrame
+
+
+@pytest.fixture
+def int_frame_const_col():
+    """
+    Fixture for DataFrame of ints which are constant per column
+
+    Columns are ['A', 'B', 'C'], with values (per column): [1, 2, 3]
+    """
+    df = DataFrame(
+        np.tile(np.arange(3, dtype="int64"), 6).reshape(6, -1) + 1,
+        columns=["A", "B", "C"],
+    )
+    return df

.venv/Lib/site-packages/pandas/tests/apply/test_frame_apply_relabeling.py

@@ -0,0 +1,97 @@
+import numpy as np
+
+import pandas as pd
+import pandas._testing as tm
+
+
+def test_agg_relabel():
+    # GH 26513
+    df = pd.DataFrame({"A": [1, 2, 1, 2], "B": [1, 2, 3, 4], "C": [3, 4, 5, 6]})
+
+    # simplest case with one column, one func
+    result = df.agg(foo=("B", "sum"))
+    expected = pd.DataFrame({"B": [10]}, index=pd.Index(["foo"]))
+    tm.assert_frame_equal(result, expected)
+
+    # test on same column with different methods
+    result = df.agg(foo=("B", "sum"), bar=("B", "min"))
+    expected = pd.DataFrame({"B": [10, 1]}, index=pd.Index(["foo", "bar"]))
+
+    tm.assert_frame_equal(result, expected)
+
+
+def test_agg_relabel_multi_columns_multi_methods():
+    # GH 26513, test on multiple columns with multiple methods
+    df = pd.DataFrame({"A": [1, 2, 1, 2], "B": [1, 2, 3, 4], "C": [3, 4, 5, 6]})
+    result = df.agg(
+        foo=("A", "sum"),
+        bar=("B", "mean"),
+        cat=("A", "min"),
+        dat=("B", "max"),
+        f=("A", "max"),
+        g=("C", "min"),
+    )
+    expected = pd.DataFrame(
+        {
+            "A": [6.0, np.nan, 1.0, np.nan, 2.0, np.nan],
+            "B": [np.nan, 2.5, np.nan, 4.0, np.nan, np.nan],
+            "C": [np.nan, np.nan, np.nan, np.nan, np.nan, 3.0],
+        },
+        index=pd.Index(["foo", "bar", "cat", "dat", "f", "g"]),
+    )
+    tm.assert_frame_equal(result, expected)
+
+
+def test_agg_relabel_partial_functions():
+    # GH 26513, test on partial, functools or more complex cases
+    df = pd.DataFrame({"A": [1, 2, 1, 2], "B": [1, 2, 3, 4], "C": [3, 4, 5, 6]})
+    result = df.agg(foo=("A", np.mean), bar=("A", "mean"), cat=("A", min))
+    expected = pd.DataFrame(
+        {"A": [1.5, 1.5, 1.0]}, index=pd.Index(["foo", "bar", "cat"])
+    )
+    tm.assert_frame_equal(result, expected)
+
+    result = df.agg(
+        foo=("A", min),
+        bar=("A", np.min),
+        cat=("B", max),
+        dat=("C", "min"),
+        f=("B", np.sum),
+        kk=("B", lambda x: min(x)),
+    )
+    expected = pd.DataFrame(
+        {
+            "A": [1.0, 1.0, np.nan, np.nan, np.nan, np.nan],
+            "B": [np.nan, np.nan, 4.0, np.nan, 10.0, 1.0],
+            "C": [np.nan, np.nan, np.nan, 3.0, np.nan, np.nan],
+        },
+        index=pd.Index(["foo", "bar", "cat", "dat", "f", "kk"]),
+    )
+    tm.assert_frame_equal(result, expected)
+
+
+def test_agg_namedtuple():
+    # GH 26513
+    df = pd.DataFrame({"A": [0, 1], "B": [1, 2]})
+    result = df.agg(
+        foo=pd.NamedAgg("B", "sum"),
+        bar=pd.NamedAgg("B", min),
+        cat=pd.NamedAgg(column="B", aggfunc="count"),
+        fft=pd.NamedAgg("B", aggfunc="max"),
+    )
+
+    expected = pd.DataFrame(
+        {"B": [3, 1, 2, 2]}, index=pd.Index(["foo", "bar", "cat", "fft"])
+    )
+    tm.assert_frame_equal(result, expected)
+
+    result = df.agg(
+        foo=pd.NamedAgg("A", "min"),
+        bar=pd.NamedAgg(column="B", aggfunc="max"),
+        cat=pd.NamedAgg(column="A", aggfunc="max"),
+    )
+    expected = pd.DataFrame(
+        {"A": [0.0, np.nan, 1.0], "B": [np.nan, 2.0, np.nan]},
+        index=pd.Index(["foo", "bar", "cat"]),
+    )
+    tm.assert_frame_equal(result, expected)

.venv/Lib/site-packages/pandas/tests/apply/test_frame_transform.py

@@ -0,0 +1,249 @@
+import numpy as np
+import pytest
+
+from pandas import (
+    DataFrame,
+    MultiIndex,
+    Series,
+)
+import pandas._testing as tm
+from pandas.tests.apply.common import frame_transform_kernels
+from pandas.tests.frame.common import zip_frames
+
+
+def unpack_obj(obj, klass, axis):
+    """
+    Helper to ensure we have the right type of object for a test parametrized
+    over frame_or_series.
+    """
+    if klass is not DataFrame:
+        obj = obj["A"]
+        if axis != 0:
+            pytest.skip(f"Test is only for DataFrame with axis={axis}")
+    return obj
+
+
+def test_transform_ufunc(axis, float_frame, frame_or_series):
+    # GH 35964
+    obj = unpack_obj(float_frame, frame_or_series, axis)
+
+    with np.errstate(all="ignore"):
+        f_sqrt = np.sqrt(obj)
+
+    # ufunc
+    result = obj.transform(np.sqrt, axis=axis)
+    expected = f_sqrt
+    tm.assert_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "ops, names",
+    [
+        ([np.sqrt], ["sqrt"]),
+        ([np.abs, np.sqrt], ["absolute", "sqrt"]),
+        (np.array([np.sqrt]), ["sqrt"]),
+        (np.array([np.abs, np.sqrt]), ["absolute", "sqrt"]),
+    ],
+)
+def test_transform_listlike(axis, float_frame, ops, names):
+    # GH 35964
+    other_axis = 1 if axis in {0, "index"} else 0
+    with np.errstate(all="ignore"):
+        expected = zip_frames([op(float_frame) for op in ops], axis=other_axis)
+    if axis in {0, "index"}:
+        expected.columns = MultiIndex.from_product([float_frame.columns, names])
+    else:
+        expected.index = MultiIndex.from_product([float_frame.index, names])
+    result = float_frame.transform(ops, axis=axis)
+    tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize("ops", [[], np.array([])])
+def test_transform_empty_listlike(float_frame, ops, frame_or_series):
+    obj = unpack_obj(float_frame, frame_or_series, 0)
+
+    with pytest.raises(ValueError, match="No transform functions were provided"):
+        obj.transform(ops)
+
+
+@pytest.mark.parametrize("box", [dict, Series])
+def test_transform_dictlike(axis, float_frame, box):
+    # GH 35964
+    if axis == 0 or axis == "index":
+        e = float_frame.columns[0]
+        expected = float_frame[[e]].transform(np.abs)
+    else:
+        e = float_frame.index[0]
+        expected = float_frame.iloc[[0]].transform(np.abs)
+    result = float_frame.transform(box({e: np.abs}), axis=axis)
+    tm.assert_frame_equal(result, expected)
+
+
+def test_transform_dictlike_mixed():
+    # GH 40018 - mix of lists and non-lists in values of a dictionary
+    df = DataFrame({"a": [1, 2], "b": [1, 4], "c": [1, 4]})
+    result = df.transform({"b": ["sqrt", "abs"], "c": "sqrt"})
+    expected = DataFrame(
+        [[1.0, 1, 1.0], [2.0, 4, 2.0]],
+        columns=MultiIndex([("b", "c"), ("sqrt", "abs")], [(0, 0, 1), (0, 1, 0)]),
+    )
+    tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "ops",
+    [
+        {},
+        {"A": []},
+        {"A": [], "B": "cumsum"},
+        {"A": "cumsum", "B": []},
+        {"A": [], "B": ["cumsum"]},
+        {"A": ["cumsum"], "B": []},
+    ],
+)
+def test_transform_empty_dictlike(float_frame, ops, frame_or_series):
+    obj = unpack_obj(float_frame, frame_or_series, 0)
+
+    with pytest.raises(ValueError, match="No transform functions were provided"):
+        obj.transform(ops)
+
+
+@pytest.mark.parametrize("use_apply", [True, False])
+def test_transform_udf(axis, float_frame, use_apply, frame_or_series):
+    # GH 35964
+    obj = unpack_obj(float_frame, frame_or_series, axis)
+
+    # transform uses UDF either via apply or passing the entire DataFrame
+    def func(x):
+        # transform is using apply iff x is not a DataFrame
+        if use_apply == isinstance(x, frame_or_series):
+            # Force transform to fallback
+            raise ValueError
+        return x + 1
+
+    result = obj.transform(func, axis=axis)
+    expected = obj + 1
+    tm.assert_equal(result, expected)
+
+
+wont_fail = ["ffill", "bfill", "fillna", "pad", "backfill", "shift"]
+frame_kernels_raise = [x for x in frame_transform_kernels if x not in wont_fail]
+
+
+@pytest.mark.parametrize("op", [*frame_kernels_raise, lambda x: x + 1])
+def test_transform_bad_dtype(op, frame_or_series, request):
+    # GH 35964
+    if op == "rank":
+        request.node.add_marker(
+            pytest.mark.xfail(
+                raises=ValueError, reason="GH 40418: rank does not raise a TypeError"
+            )
+        )
+
+    obj = DataFrame({"A": 3 * [object]})  # DataFrame that will fail on most transforms
+    obj = tm.get_obj(obj, frame_or_series)
+
+    # tshift is deprecated
+    warn = None if op != "tshift" else FutureWarning
+    with tm.assert_produces_warning(warn):
+        with pytest.raises(TypeError, match="unsupported operand|not supported"):
+            obj.transform(op)
+        with pytest.raises(TypeError, match="Transform function failed"):
+            obj.transform([op])
+        with pytest.raises(TypeError, match="Transform function failed"):
+            obj.transform({"A": op})
+        with pytest.raises(TypeError, match="Transform function failed"):
+            obj.transform({"A": [op]})
+
+
+@pytest.mark.parametrize("op", frame_kernels_raise)
+def test_transform_partial_failure_typeerror(op):
+    # GH 35964
+
+    # Using object makes most transform kernels fail
+    df = DataFrame({"A": 3 * [object], "B": [1, 2, 3]})
+
+    expected = df[["B"]].transform([op])
+    match = r"\['A'\] did not transform successfully"
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = df.transform([op])
+    tm.assert_equal(result, expected)
+
+    expected = df[["B"]].transform({"B": op})
+    match = r"\['A'\] did not transform successfully"
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = df.transform({"A": op, "B": op})
+    tm.assert_equal(result, expected)
+
+    expected = df[["B"]].transform({"B": [op]})
+    match = r"\['A'\] did not transform successfully"
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = df.transform({"A": [op], "B": [op]})
+    tm.assert_equal(result, expected)
+
+    expected = df.transform({"A": ["shift"], "B": [op]})
+    match = rf"\['{op}'\] did not transform successfully"
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = df.transform({"A": [op, "shift"], "B": [op]})
+    tm.assert_equal(result, expected)
+
+
+def test_transform_partial_failure_valueerror():
+    # GH 40211
+    match = ".*did not transform successfully"
+
+    def op(x):
+        if np.sum(np.sum(x)) < 10:
+            raise ValueError
+        return x
+
+    df = DataFrame({"A": [1, 2, 3], "B": [400, 500, 600]})
+
+    expected = df[["B"]].transform([op])
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = df.transform([op])
+    tm.assert_equal(result, expected)
+
+    expected = df[["B"]].transform({"B": op})
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = df.transform({"A": op, "B": op})
+    tm.assert_equal(result, expected)
+
+    expected = df[["B"]].transform({"B": [op]})
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = df.transform({"A": [op], "B": [op]})
+    tm.assert_equal(result, expected)
+
+    expected = df.transform({"A": ["shift"], "B": [op]})
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = df.transform({"A": [op, "shift"], "B": [op]})
+    tm.assert_equal(result, expected)
+
+
+@pytest.mark.parametrize("use_apply", [True, False])
+def test_transform_passes_args(use_apply, frame_or_series):
+    # GH 35964
+    # transform uses UDF either via apply or passing the entire DataFrame
+    expected_args = [1, 2]
+    expected_kwargs = {"c": 3}
+
+    def f(x, a, b, c):
+        # transform is using apply iff x is not a DataFrame
+        if use_apply == isinstance(x, frame_or_series):
+            # Force transform to fallback
+            raise ValueError
+        assert [a, b] == expected_args
+        assert c == expected_kwargs["c"]
+        return x
+
+    frame_or_series([1]).transform(f, 0, *expected_args, **expected_kwargs)
+
+
+def test_transform_empty_dataframe():
+    # https://github.com/pandas-dev/pandas/issues/39636
+    df = DataFrame([], columns=["col1", "col2"])
+    result = df.transform(lambda x: x + 10)
+    tm.assert_frame_equal(result, df)
+
+    result = df["col1"].transform(lambda x: x + 10)
+    tm.assert_series_equal(result, df["col1"])

.venv/Lib/site-packages/pandas/tests/apply/test_invalid_arg.py

@@ -0,0 +1,359 @@
+# Tests specifically aimed at detecting bad arguments.
+# This file is organized by reason for exception.
+#     1. always invalid argument values
+#     2. missing column(s)
+#     3. incompatible ops/dtype/args/kwargs
+#     4. invalid result shape/type
+# If your test does not fit into one of these categories, add to this list.
+
+from itertools import chain
+import re
+
+import numpy as np
+import pytest
+
+from pandas import (
+    Categorical,
+    DataFrame,
+    Series,
+    date_range,
+    notna,
+)
+import pandas._testing as tm
+from pandas.core.base import SpecificationError
+
+
+@pytest.mark.parametrize("result_type", ["foo", 1])
+def test_result_type_error(result_type, int_frame_const_col):
+    # allowed result_type
+    df = int_frame_const_col
+
+    msg = (
+        "invalid value for result_type, must be one of "
+        "{None, 'reduce', 'broadcast', 'expand'}"
+    )
+    with pytest.raises(ValueError, match=msg):
+        df.apply(lambda x: [1, 2, 3], axis=1, result_type=result_type)
+
+
+def test_apply_invalid_axis_value():
+    df = DataFrame([[1, 2, 3], [4, 5, 6], [7, 8, 9]], index=["a", "a", "c"])
+    msg = "No axis named 2 for object type DataFrame"
+    with pytest.raises(ValueError, match=msg):
+        df.apply(lambda x: x, 2)
+
+
+def test_applymap_invalid_na_action(float_frame):
+    # GH 23803
+    with pytest.raises(ValueError, match="na_action must be .*Got 'abc'"):
+        float_frame.applymap(lambda x: len(str(x)), na_action="abc")
+
+
+def test_agg_raises():
+    # GH 26513
+    df = DataFrame({"A": [0, 1], "B": [1, 2]})
+    msg = "Must provide"
+
+    with pytest.raises(TypeError, match=msg):
+        df.agg()
+
+
+def test_map_with_invalid_na_action_raises():
+    # https://github.com/pandas-dev/pandas/issues/32815
+    s = Series([1, 2, 3])
+    msg = "na_action must either be 'ignore' or None"
+    with pytest.raises(ValueError, match=msg):
+        s.map(lambda x: x, na_action="____")
+
+
+def test_map_categorical_na_action():
+    values = Categorical(list("ABBABCD"), categories=list("DCBA"), ordered=True)
+    s = Series(values, name="XX", index=list("abcdefg"))
+    with pytest.raises(NotImplementedError, match=tm.EMPTY_STRING_PATTERN):
+        s.map(lambda x: x, na_action="ignore")
+
+
+def test_map_datetimetz_na_action():
+    values = date_range("2011-01-01", "2011-01-02", freq="H").tz_localize("Asia/Tokyo")
+    s = Series(values, name="XX")
+    with pytest.raises(NotImplementedError, match=tm.EMPTY_STRING_PATTERN):
+        s.map(lambda x: x, na_action="ignore")
+
+
+@pytest.mark.parametrize("box", [DataFrame, Series])
+@pytest.mark.parametrize("method", ["apply", "agg", "transform"])
+@pytest.mark.parametrize("func", [{"A": {"B": "sum"}}, {"A": {"B": ["sum"]}}])
+def test_nested_renamer(box, method, func):
+    # GH 35964
+    obj = box({"A": [1]})
+    match = "nested renamer is not supported"
+    with pytest.raises(SpecificationError, match=match):
+        getattr(obj, method)(func)
+
+
+@pytest.mark.parametrize(
+    "renamer",
+    [{"foo": ["min", "max"]}, {"foo": ["min", "max"], "bar": ["sum", "mean"]}],
+)
+def test_series_nested_renamer(renamer):
+    s = Series(range(6), dtype="int64", name="series")
+    msg = "nested renamer is not supported"
+    with pytest.raises(SpecificationError, match=msg):
+        s.agg(renamer)
+
+
+def test_apply_dict_depr():
+
+    tsdf = DataFrame(
+        np.random.randn(10, 3),
+        columns=["A", "B", "C"],
+        index=date_range("1/1/2000", periods=10),
+    )
+    msg = "nested renamer is not supported"
+    with pytest.raises(SpecificationError, match=msg):
+        tsdf.A.agg({"foo": ["sum", "mean"]})
+
+
+@pytest.mark.parametrize("method", ["agg", "transform"])
+def test_dict_nested_renaming_depr(method):
+
+    df = DataFrame({"A": range(5), "B": 5})
+
+    # nested renaming
+    msg = r"nested renamer is not supported"
+    with pytest.raises(SpecificationError, match=msg):
+        getattr(df, method)({"A": {"foo": "min"}, "B": {"bar": "max"}})
+
+
+@pytest.mark.parametrize("method", ["apply", "agg", "transform"])
+@pytest.mark.parametrize("func", [{"B": "sum"}, {"B": ["sum"]}])
+def test_missing_column(method, func):
+    # GH 40004
+    obj = DataFrame({"A": [1]})
+    match = re.escape("Column(s) ['B'] do not exist")
+    with pytest.raises(KeyError, match=match):
+        getattr(obj, method)(func)
+
+
+def test_transform_mixed_column_name_dtypes():
+    # GH39025
+    df = DataFrame({"a": ["1"]})
+    msg = r"Column\(s\) \[1, 'b'\] do not exist"
+    with pytest.raises(KeyError, match=msg):
+        df.transform({"a": int, 1: str, "b": int})
+
+
+@pytest.mark.parametrize(
+    "how, args", [("pct_change", ()), ("nsmallest", (1, ["a", "b"])), ("tail", 1)]
+)
+def test_apply_str_axis_1_raises(how, args):
+    # GH 39211 - some ops don't support axis=1
+    df = DataFrame({"a": [1, 2], "b": [3, 4]})
+    msg = f"Operation {how} does not support axis=1"
+    with pytest.raises(ValueError, match=msg):
+        df.apply(how, axis=1, args=args)
+
+
+def test_transform_axis_1_raises():
+    # GH 35964
+    msg = "No axis named 1 for object type Series"
+    with pytest.raises(ValueError, match=msg):
+        Series([1]).transform("sum", axis=1)
+
+
+def test_apply_modify_traceback():
+    data = 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),
+        }
+    )
+
+    data.loc[4, "C"] = np.nan
+
+    def transform(row):
+        if row["C"].startswith("shin") and row["A"] == "foo":
+            row["D"] = 7
+        return row
+
+    def transform2(row):
+        if notna(row["C"]) and row["C"].startswith("shin") and row["A"] == "foo":
+            row["D"] = 7
+        return row
+
+    msg = "'float' object has no attribute 'startswith'"
+    with pytest.raises(AttributeError, match=msg):
+        data.apply(transform, axis=1)
+
+
+@pytest.mark.parametrize(
+    "df, func, expected",
+    tm.get_cython_table_params(
+        DataFrame([["a", "b"], ["b", "a"]]), [["cumprod", TypeError]]
+    ),
+)
+def test_agg_cython_table_raises_frame(df, func, expected, axis):
+    # GH 21224
+    msg = "can't multiply sequence by non-int of type 'str'"
+    with pytest.raises(expected, match=msg):
+        df.agg(func, axis=axis)
+
+
+@pytest.mark.parametrize(
+    "series, func, expected",
+    chain(
+        tm.get_cython_table_params(
+            Series("a b c".split()),
+            [
+                ("mean", TypeError),  # mean raises TypeError
+                ("prod", TypeError),
+                ("std", TypeError),
+                ("var", TypeError),
+                ("median", TypeError),
+                ("cumprod", TypeError),
+            ],
+        )
+    ),
+)
+def test_agg_cython_table_raises_series(series, func, expected):
+    # GH21224
+    msg = r"[Cc]ould not convert|can't multiply sequence by non-int of type"
+    with pytest.raises(expected, match=msg):
+        # e.g. Series('a b'.split()).cumprod() will raise
+        series.agg(func)
+
+
+def test_agg_none_to_type():
+    # GH 40543
+    df = DataFrame({"a": [None]})
+    msg = re.escape("int() argument must be a string")
+    with pytest.raises(TypeError, match=msg):
+        df.agg({"a": int})
+
+
+def test_transform_none_to_type():
+    # GH#34377
+    df = DataFrame({"a": [None]})
+    msg = "Transform function failed"
+    with pytest.raises(TypeError, match=msg):
+        df.transform({"a": int})
+
+
+@pytest.mark.parametrize(
+    "func",
+    [
+        lambda x: np.array([1, 2]).reshape(-1, 2),
+        lambda x: [1, 2],
+        lambda x: Series([1, 2]),
+    ],
+)
+def test_apply_broadcast_error(int_frame_const_col, func):
+    df = int_frame_const_col
+
+    # > 1 ndim
+    msg = "too many dims to broadcast|cannot broadcast result"
+    with pytest.raises(ValueError, match=msg):
+        df.apply(func, axis=1, result_type="broadcast")
+
+
+def test_transform_and_agg_err_agg(axis, float_frame):
+    # cannot both transform and agg
+    msg = "cannot combine transform and aggregation operations"
+    with pytest.raises(ValueError, match=msg):
+        with np.errstate(all="ignore"):
+            float_frame.agg(["max", "sqrt"], axis=axis)
+
+
+@pytest.mark.parametrize(
+    "func, msg",
+    [
+        (["sqrt", "max"], "cannot combine transform and aggregation"),
+        (
+            {"foo": np.sqrt, "bar": "sum"},
+            "cannot perform both aggregation and transformation",
+        ),
+    ],
+)
+def test_transform_and_agg_err_series(string_series, func, msg):
+    # we are trying to transform with an aggregator
+    with pytest.raises(ValueError, match=msg):
+        with np.errstate(all="ignore"):
+            string_series.agg(func)
+
+
+@pytest.mark.parametrize("func", [["max", "min"], ["max", "sqrt"]])
+def test_transform_wont_agg_frame(axis, float_frame, func):
+    # GH 35964
+    # cannot both transform and agg
+    msg = "Function did not transform"
+    with pytest.raises(ValueError, match=msg):
+        float_frame.transform(func, axis=axis)
+
+
+@pytest.mark.parametrize("func", [["min", "max"], ["sqrt", "max"]])
+def test_transform_wont_agg_series(string_series, func):
+    # GH 35964
+    # we are trying to transform with an aggregator
+    msg = "Function did not transform"
+
+    warn = RuntimeWarning if func[0] == "sqrt" else None
+    warn_msg = "invalid value encountered in sqrt"
+    with pytest.raises(ValueError, match=msg):
+        with tm.assert_produces_warning(warn, match=warn_msg):
+            string_series.transform(func)
+
+
+@pytest.mark.parametrize(
+    "op_wrapper", [lambda x: x, lambda x: [x], lambda x: {"A": x}, lambda x: {"A": [x]}]
+)
+@pytest.mark.filterwarnings("ignore:.*Select only valid:FutureWarning")
+def test_transform_reducer_raises(all_reductions, frame_or_series, op_wrapper):
+    # GH 35964
+    op = op_wrapper(all_reductions)
+
+    obj = DataFrame({"A": [1, 2, 3]})
+    obj = tm.get_obj(obj, frame_or_series)
+
+    msg = "Function did not transform"
+    with pytest.raises(ValueError, match=msg):
+        obj.transform(op)

.venv/Lib/site-packages/pandas/tests/apply/test_series_apply.py

@@ -0,0 +1,889 @@
+from collections import (
+    Counter,
+    defaultdict,
+)
+
+import numpy as np
+import pytest
+
+import pandas as pd
+from pandas import (
+    DataFrame,
+    Index,
+    MultiIndex,
+    Series,
+    concat,
+    isna,
+    timedelta_range,
+)
+import pandas._testing as tm
+from pandas.tests.apply.common import series_transform_kernels
+
+
+def test_series_map_box_timedelta():
+    # GH#11349
+    ser = Series(timedelta_range("1 day 1 s", periods=5, freq="h"))
+
+    def f(x):
+        return x.total_seconds()
+
+    ser.map(f)
+    ser.apply(f)
+    DataFrame(ser).applymap(f)
+
+
+def test_apply(datetime_series):
+    with np.errstate(all="ignore"):
+        tm.assert_series_equal(datetime_series.apply(np.sqrt), np.sqrt(datetime_series))
+
+        # element-wise apply
+        import math
+
+        tm.assert_series_equal(datetime_series.apply(math.exp), np.exp(datetime_series))
+
+    # empty series
+    s = Series(dtype=object, name="foo", index=Index([], name="bar"))
+    rs = s.apply(lambda x: x)
+    tm.assert_series_equal(s, rs)
+
+    # check all metadata (GH 9322)
+    assert s is not rs
+    assert s.index is rs.index
+    assert s.dtype == rs.dtype
+    assert s.name == rs.name
+
+    # index but no data
+    s = Series(index=[1, 2, 3], dtype=np.float64)
+    rs = s.apply(lambda x: x)
+    tm.assert_series_equal(s, rs)
+
+
+def test_apply_same_length_inference_bug():
+    s = Series([1, 2])
+
+    def f(x):
+        return (x, x + 1)
+
+    result = s.apply(f)
+    expected = s.map(f)
+    tm.assert_series_equal(result, expected)
+
+    s = Series([1, 2, 3])
+    result = s.apply(f)
+    expected = s.map(f)
+    tm.assert_series_equal(result, expected)
+
+
+def test_apply_dont_convert_dtype():
+    s = Series(np.random.randn(10))
+
+    def f(x):
+        return x if x > 0 else np.nan
+
+    result = s.apply(f, convert_dtype=False)
+    assert result.dtype == object
+
+
+def test_apply_args():
+    s = Series(["foo,bar"])
+
+    result = s.apply(str.split, args=(",",))
+    assert result[0] == ["foo", "bar"]
+    assert isinstance(result[0], list)
+
+
+@pytest.mark.parametrize(
+    "args, kwargs, increment",
+    [((), {}, 0), ((), {"a": 1}, 1), ((2, 3), {}, 32), ((1,), {"c": 2}, 201)],
+)
+def test_agg_args(args, kwargs, increment):
+    # GH 43357
+    def f(x, a=0, b=0, c=0):
+        return x + a + 10 * b + 100 * c
+
+    s = Series([1, 2])
+    result = s.agg(f, 0, *args, **kwargs)
+    expected = s + increment
+    tm.assert_series_equal(result, expected)
+
+
+def test_series_map_box_timestamps():
+    # GH#2689, GH#2627
+    ser = Series(pd.date_range("1/1/2000", periods=10))
+
+    def func(x):
+        return (x.hour, x.day, x.month)
+
+    # it works!
+    ser.map(func)
+    ser.apply(func)
+
+
+def test_series_map_stringdtype(any_string_dtype):
+    # map test on StringDType, GH#40823
+    ser1 = Series(
+        data=["cat", "dog", "rabbit"],
+        index=["id1", "id2", "id3"],
+        dtype=any_string_dtype,
+    )
+    ser2 = Series(data=["id3", "id2", "id1", "id7000"], dtype=any_string_dtype)
+    result = ser2.map(ser1)
+    expected = Series(data=["rabbit", "dog", "cat", pd.NA], dtype=any_string_dtype)
+
+    tm.assert_series_equal(result, expected)
+
+
+def test_apply_box():
+    # ufunc will not be boxed. Same test cases as the test_map_box
+    vals = [pd.Timestamp("2011-01-01"), pd.Timestamp("2011-01-02")]
+    s = Series(vals)
+    assert s.dtype == "datetime64[ns]"
+    # boxed value must be Timestamp instance
+    res = s.apply(lambda x: f"{type(x).__name__}_{x.day}_{x.tz}")
+    exp = Series(["Timestamp_1_None", "Timestamp_2_None"])
+    tm.assert_series_equal(res, exp)
+
+    vals = [
+        pd.Timestamp("2011-01-01", tz="US/Eastern"),
+        pd.Timestamp("2011-01-02", tz="US/Eastern"),
+    ]
+    s = Series(vals)
+    assert s.dtype == "datetime64[ns, US/Eastern]"
+    res = s.apply(lambda x: f"{type(x).__name__}_{x.day}_{x.tz}")
+    exp = Series(["Timestamp_1_US/Eastern", "Timestamp_2_US/Eastern"])
+    tm.assert_series_equal(res, exp)
+
+    # timedelta
+    vals = [pd.Timedelta("1 days"), pd.Timedelta("2 days")]
+    s = Series(vals)
+    assert s.dtype == "timedelta64[ns]"
+    res = s.apply(lambda x: f"{type(x).__name__}_{x.days}")
+    exp = Series(["Timedelta_1", "Timedelta_2"])
+    tm.assert_series_equal(res, exp)
+
+    # period
+    vals = [pd.Period("2011-01-01", freq="M"), pd.Period("2011-01-02", freq="M")]
+    s = Series(vals)
+    assert s.dtype == "Period[M]"
+    res = s.apply(lambda x: f"{type(x).__name__}_{x.freqstr}")
+    exp = Series(["Period_M", "Period_M"])
+    tm.assert_series_equal(res, exp)
+
+
+def test_apply_datetimetz():
+    values = pd.date_range("2011-01-01", "2011-01-02", freq="H").tz_localize(
+        "Asia/Tokyo"
+    )
+    s = Series(values, name="XX")
+
+    result = s.apply(lambda x: x + pd.offsets.Day())
+    exp_values = pd.date_range("2011-01-02", "2011-01-03", freq="H").tz_localize(
+        "Asia/Tokyo"
+    )
+    exp = Series(exp_values, name="XX")
+    tm.assert_series_equal(result, exp)
+
+    # change dtype
+    # GH 14506 : Returned dtype changed from int32 to int64
+    result = s.apply(lambda x: x.hour)
+    exp = Series(list(range(24)) + [0], name="XX", dtype=np.int64)
+    tm.assert_series_equal(result, exp)
+
+    # not vectorized
+    def f(x):
+        if not isinstance(x, pd.Timestamp):
+            raise ValueError
+        return str(x.tz)
+
+    result = s.map(f)
+    exp = Series(["Asia/Tokyo"] * 25, name="XX")
+    tm.assert_series_equal(result, exp)
+
+
+def test_apply_categorical():
+    values = pd.Categorical(list("ABBABCD"), categories=list("DCBA"), ordered=True)
+    ser = Series(values, name="XX", index=list("abcdefg"))
+    result = ser.apply(lambda x: x.lower())
+
+    # should be categorical dtype when the number of categories are
+    # the same
+    values = pd.Categorical(list("abbabcd"), categories=list("dcba"), ordered=True)
+    exp = Series(values, name="XX", index=list("abcdefg"))
+    tm.assert_series_equal(result, exp)
+    tm.assert_categorical_equal(result.values, exp.values)
+
+    result = ser.apply(lambda x: "A")
+    exp = Series(["A"] * 7, name="XX", index=list("abcdefg"))
+    tm.assert_series_equal(result, exp)
+    assert result.dtype == object
+
+
+@pytest.mark.parametrize("series", [["1-1", "1-1", np.NaN], ["1-1", "1-2", np.NaN]])
+def test_apply_categorical_with_nan_values(series):
+    # GH 20714 bug fixed in: GH 24275
+    s = Series(series, dtype="category")
+    result = s.apply(lambda x: x.split("-")[0])
+    result = result.astype(object)
+    expected = Series(["1", "1", np.NaN], dtype="category")
+    expected = expected.astype(object)
+    tm.assert_series_equal(result, expected)
+
+
+def test_apply_empty_integer_series_with_datetime_index():
+    # GH 21245
+    s = Series([], index=pd.date_range(start="2018-01-01", periods=0), dtype=int)
+    result = s.apply(lambda x: x)
+    tm.assert_series_equal(result, s)
+
+
+def test_transform(string_series):
+    # transforming functions
+
+    with np.errstate(all="ignore"):
+
+        f_sqrt = np.sqrt(string_series)
+        f_abs = np.abs(string_series)
+
+        # ufunc
+        result = string_series.apply(np.sqrt)
+        expected = f_sqrt.copy()
+        tm.assert_series_equal(result, expected)
+
+        # list-like
+        result = string_series.apply([np.sqrt])
+        expected = f_sqrt.to_frame().copy()
+        expected.columns = ["sqrt"]
+        tm.assert_frame_equal(result, expected)
+
+        result = string_series.apply(["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
+        expected = concat([f_sqrt, f_abs], axis=1)
+        expected.columns = ["sqrt", "absolute"]
+        result = string_series.apply([np.sqrt, np.abs])
+        tm.assert_frame_equal(result, expected)
+
+        # dict, provide renaming
+        expected = concat([f_sqrt, f_abs], axis=1)
+        expected.columns = ["foo", "bar"]
+        expected = expected.unstack().rename("series")
+
+        result = string_series.apply({"foo": np.sqrt, "bar": np.abs})
+        tm.assert_series_equal(result.reindex_like(expected), expected)
+
+
+@pytest.mark.parametrize("op", series_transform_kernels)
+def test_transform_partial_failure(op, request):
+    # GH 35964
+    if op in ("ffill", "bfill", "pad", "backfill", "shift"):
+        request.node.add_marker(
+            pytest.mark.xfail(
+                raises=AssertionError, reason=f"{op} is successful on any dtype"
+            )
+        )
+    if op in ("rank", "fillna"):
+        pytest.skip(f"{op} doesn't raise TypeError on object")
+
+    # Using object makes most transform kernels fail
+    ser = Series(3 * [object])
+
+    expected = ser.transform(["shift"])
+    match = rf"\['{op}'\] did not transform successfully"
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = ser.transform([op, "shift"])
+    tm.assert_equal(result, expected)
+
+    expected = ser.transform({"B": "shift"})
+    match = r"\['A'\] did not transform successfully"
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = ser.transform({"A": op, "B": "shift"})
+    tm.assert_equal(result, expected)
+
+    expected = ser.transform({"B": ["shift"]})
+    match = r"\['A'\] did not transform successfully"
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = ser.transform({"A": [op], "B": ["shift"]})
+    tm.assert_equal(result, expected)
+
+    match = r"\['B'\] did not transform successfully"
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        expected = ser.transform({"A": ["shift"], "B": [op]})
+    match = rf"\['{op}'\] did not transform successfully"
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = ser.transform({"A": [op, "shift"], "B": [op]})
+    tm.assert_equal(result, expected)
+
+
+def test_transform_partial_failure_valueerror():
+    # GH 40211
+    match = ".*did not transform successfully"
+
+    def noop(x):
+        return x
+
+    def raising_op(_):
+        raise ValueError
+
+    ser = Series(3 * [object])
+
+    expected = ser.transform([noop])
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = ser.transform([noop, raising_op])
+    tm.assert_equal(result, expected)
+
+    expected = ser.transform({"B": noop})
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = ser.transform({"A": raising_op, "B": noop})
+    tm.assert_equal(result, expected)
+
+    expected = ser.transform({"B": [noop]})
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = ser.transform({"A": [raising_op], "B": [noop]})
+    tm.assert_equal(result, expected)
+
+    expected = ser.transform({"A": [noop], "B": [noop]})
+    with tm.assert_produces_warning(FutureWarning, match=match):
+        result = ser.transform({"A": [noop, raising_op], "B": [noop]})
+    tm.assert_equal(result, expected)
+
+
+def test_demo():
+    # demonstration tests
+    s = Series(range(6), dtype="int64", name="series")
+
+    result = s.agg(["min", "max"])
+    expected = Series([0, 5], index=["min", "max"], name="series")
+    tm.assert_series_equal(result, expected)
+
+    result = s.agg({"foo": "min"})
+    expected = Series([0], index=["foo"], name="series")
+    tm.assert_series_equal(result, expected)
+
+
+def test_agg_apply_evaluate_lambdas_the_same(string_series):
+    # test that we are evaluating row-by-row first
+    # before vectorized evaluation
+    result = string_series.apply(lambda x: str(x))
+    expected = string_series.agg(lambda x: str(x))
+    tm.assert_series_equal(result, expected)
+
+    result = string_series.apply(str)
+    expected = string_series.agg(str)
+    tm.assert_series_equal(result, expected)
+
+
+def test_with_nested_series(datetime_series):
+    # GH 2316
+    # .agg with a reducer and a transform, what to do
+    result = datetime_series.apply(lambda x: Series([x, x**2], index=["x", "x^2"]))
+    expected = DataFrame({"x": datetime_series, "x^2": datetime_series**2})
+    tm.assert_frame_equal(result, expected)
+
+    result = datetime_series.agg(lambda x: Series([x, x**2], index=["x", "x^2"]))
+    tm.assert_frame_equal(result, expected)
+
+
+def test_replicate_describe(string_series):
+    # this also tests a result set that is all scalars
+    expected = string_series.describe()
+    result = string_series.apply(
+        {
+            "count": "count",
+            "mean": "mean",
+            "std": "std",
+            "min": "min",
+            "25%": lambda x: x.quantile(0.25),
+            "50%": "median",
+            "75%": lambda x: x.quantile(0.75),
+            "max": "max",
+        }
+    )
+    tm.assert_series_equal(result, expected)
+
+
+def test_reduce(string_series):
+    # reductions with named functions
+    result = string_series.agg(["sum", "mean"])
+    expected = Series(
+        [string_series.sum(), string_series.mean()],
+        ["sum", "mean"],
+        name=string_series.name,
+    )
+    tm.assert_series_equal(result, expected)
+
+
+@pytest.mark.parametrize("how", ["agg", "apply"])
+def test_non_callable_aggregates(how):
+    # test agg using non-callable series attributes
+    # GH 39116 - expand to apply
+    s = Series([1, 2, None])
+
+    # Calling agg w/ just a string arg same as calling s.arg
+    result = getattr(s, how)("size")
+    expected = s.size
+    assert result == expected
+
+    # test when mixed w/ callable reducers
+    result = getattr(s, how)(["size", "count", "mean"])
+    expected = Series({"size": 3.0, "count": 2.0, "mean": 1.5})
+    tm.assert_series_equal(result, expected)
+
+
+def test_series_apply_no_suffix_index():
+    # GH36189
+    s = Series([4] * 3)
+    result = s.apply(["sum", lambda x: x.sum(), lambda x: x.sum()])
+    expected = Series([12, 12, 12], index=["sum", "<lambda>", "<lambda>"])
+
+    tm.assert_series_equal(result, expected)
+
+
+def test_map(datetime_series):
+    index, data = tm.getMixedTypeDict()
+
+    source = Series(data["B"], index=data["C"])
+    target = Series(data["C"][:4], index=data["D"][:4])
+
+    merged = target.map(source)
+
+    for k, v in merged.items():
+        assert v == source[target[k]]
+
+    # input could be a dict
+    merged = target.map(source.to_dict())
+
+    for k, v in merged.items():
+        assert v == source[target[k]]
+
+    # function
+    result = datetime_series.map(lambda x: x * 2)
+    tm.assert_series_equal(result, datetime_series * 2)
+
+    # GH 10324
+    a = Series([1, 2, 3, 4])
+    b = Series(["even", "odd", "even", "odd"], dtype="category")
+    c = Series(["even", "odd", "even", "odd"])
+
+    exp = Series(["odd", "even", "odd", np.nan], dtype="category")
+    tm.assert_series_equal(a.map(b), exp)
+    exp = Series(["odd", "even", "odd", np.nan])
+    tm.assert_series_equal(a.map(c), exp)
+
+    a = Series(["a", "b", "c", "d"])
+    b = Series([1, 2, 3, 4], index=pd.CategoricalIndex(["b", "c", "d", "e"]))
+    c = Series([1, 2, 3, 4], index=Index(["b", "c", "d", "e"]))
+
+    exp = Series([np.nan, 1, 2, 3])
+    tm.assert_series_equal(a.map(b), exp)
+    exp = Series([np.nan, 1, 2, 3])
+    tm.assert_series_equal(a.map(c), exp)
+
+    a = Series(["a", "b", "c", "d"])
+    b = Series(
+        ["B", "C", "D", "E"],
+        dtype="category",
+        index=pd.CategoricalIndex(["b", "c", "d", "e"]),
+    )
+    c = Series(["B", "C", "D", "E"], index=Index(["b", "c", "d", "e"]))
+
+    exp = Series(
+        pd.Categorical([np.nan, "B", "C", "D"], categories=["B", "C", "D", "E"])
+    )
+    tm.assert_series_equal(a.map(b), exp)
+    exp = Series([np.nan, "B", "C", "D"])
+    tm.assert_series_equal(a.map(c), exp)
+
+
+def test_map_empty(index):
+    if isinstance(index, MultiIndex):
+        pytest.skip("Initializing a Series from a MultiIndex is not supported")
+
+    s = Series(index)
+    result = s.map({})
+
+    expected = Series(np.nan, index=s.index)
+    tm.assert_series_equal(result, expected)
+
+
+def test_map_compat():
+    # related GH 8024
+    s = Series([True, True, False], index=[1, 2, 3])
+    result = s.map({True: "foo", False: "bar"})
+    expected = Series(["foo", "foo", "bar"], index=[1, 2, 3])
+    tm.assert_series_equal(result, expected)
+
+
+def test_map_int():
+    left = Series({"a": 1.0, "b": 2.0, "c": 3.0, "d": 4})
+    right = Series({1: 11, 2: 22, 3: 33})
+
+    assert left.dtype == np.float_
+    assert issubclass(right.dtype.type, np.integer)
+
+    merged = left.map(right)
+    assert merged.dtype == np.float_
+    assert isna(merged["d"])
+    assert not isna(merged["c"])
+
+
+def test_map_type_inference():
+    s = Series(range(3))
+    s2 = s.map(lambda x: np.where(x == 0, 0, 1))
+    assert issubclass(s2.dtype.type, np.integer)
+
+
+def test_map_decimal(string_series):
+    from decimal import Decimal
+
+    result = string_series.map(lambda x: Decimal(str(x)))
+    assert result.dtype == np.object_
+    assert isinstance(result[0], Decimal)
+
+
+def test_map_na_exclusion():
+    s = Series([1.5, np.nan, 3, np.nan, 5])
+
+    result = s.map(lambda x: x * 2, na_action="ignore")
+    exp = s * 2
+    tm.assert_series_equal(result, exp)
+
+
+def test_map_dict_with_tuple_keys():
+    """
+    Due to new MultiIndex-ing behaviour in v0.14.0,
+    dicts with tuple keys passed to map were being
+    converted to a multi-index, preventing tuple values
+    from being mapped properly.
+    """
+    # GH 18496
+    df = DataFrame({"a": [(1,), (2,), (3, 4), (5, 6)]})
+    label_mappings = {(1,): "A", (2,): "B", (3, 4): "A", (5, 6): "B"}
+
+    df["labels"] = df["a"].map(label_mappings)
+    df["expected_labels"] = Series(["A", "B", "A", "B"], index=df.index)
+    # All labels should be filled now
+    tm.assert_series_equal(df["labels"], df["expected_labels"], check_names=False)
+
+
+def test_map_counter():
+    s = Series(["a", "b", "c"], index=[1, 2, 3])
+    counter = Counter()
+    counter["b"] = 5
+    counter["c"] += 1
+    result = s.map(counter)
+    expected = Series([0, 5, 1], index=[1, 2, 3])
+    tm.assert_series_equal(result, expected)
+
+
+def test_map_defaultdict():
+    s = Series([1, 2, 3], index=["a", "b", "c"])
+    default_dict = defaultdict(lambda: "blank")
+    default_dict[1] = "stuff"
+    result = s.map(default_dict)
+    expected = Series(["stuff", "blank", "blank"], index=["a", "b", "c"])
+    tm.assert_series_equal(result, expected)
+
+
+def test_map_dict_na_key():
+    # https://github.com/pandas-dev/pandas/issues/17648
+    # Checks that np.nan key is appropriately mapped
+    s = Series([1, 2, np.nan])
+    expected = Series(["a", "b", "c"])
+    result = s.map({1: "a", 2: "b", np.nan: "c"})
+    tm.assert_series_equal(result, expected)
+
+
+def test_map_dict_subclass_with_missing():
+    """
+    Test Series.map with a dictionary subclass that defines __missing__,
+    i.e. sets a default value (GH #15999).
+    """
+
+    class DictWithMissing(dict):
+        def __missing__(self, key):
+            return "missing"
+
+    s = Series([1, 2, 3])
+    dictionary = DictWithMissing({3: "three"})
+    result = s.map(dictionary)
+    expected = Series(["missing", "missing", "three"])
+    tm.assert_series_equal(result, expected)
+
+
+def test_map_dict_subclass_without_missing():
+    class DictWithoutMissing(dict):
+        pass
+
+    s = Series([1, 2, 3])
+    dictionary = DictWithoutMissing({3: "three"})
+    result = s.map(dictionary)
+    expected = Series([np.nan, np.nan, "three"])
+    tm.assert_series_equal(result, expected)
+
+
+def test_map_abc_mapping(non_dict_mapping_subclass):
+    # https://github.com/pandas-dev/pandas/issues/29733
+    # Check collections.abc.Mapping support as mapper for Series.map
+    s = Series([1, 2, 3])
+    not_a_dictionary = non_dict_mapping_subclass({3: "three"})
+    result = s.map(not_a_dictionary)
+    expected = Series([np.nan, np.nan, "three"])
+    tm.assert_series_equal(result, expected)
+
+
+def test_map_abc_mapping_with_missing(non_dict_mapping_subclass):
+    # https://github.com/pandas-dev/pandas/issues/29733
+    # Check collections.abc.Mapping support as mapper for Series.map
+    class NonDictMappingWithMissing(non_dict_mapping_subclass):
+        def __missing__(key):
+            return "missing"
+
+    s = Series([1, 2, 3])
+    not_a_dictionary = NonDictMappingWithMissing({3: "three"})
+    result = s.map(not_a_dictionary)
+    # __missing__ is a dict concept, not a Mapping concept,
+    # so it should not change the result!
+    expected = Series([np.nan, np.nan, "three"])
+    tm.assert_series_equal(result, expected)
+
+
+def test_map_box():
+    vals = [pd.Timestamp("2011-01-01"), pd.Timestamp("2011-01-02")]
+    s = Series(vals)
+    assert s.dtype == "datetime64[ns]"
+    # boxed value must be Timestamp instance
+    res = s.apply(lambda x: f"{type(x).__name__}_{x.day}_{x.tz}")
+    exp = Series(["Timestamp_1_None", "Timestamp_2_None"])
+    tm.assert_series_equal(res, exp)
+
+    vals = [
+        pd.Timestamp("2011-01-01", tz="US/Eastern"),
+        pd.Timestamp("2011-01-02", tz="US/Eastern"),
+    ]
+    s = Series(vals)
+    assert s.dtype == "datetime64[ns, US/Eastern]"
+    res = s.apply(lambda x: f"{type(x).__name__}_{x.day}_{x.tz}")
+    exp = Series(["Timestamp_1_US/Eastern", "Timestamp_2_US/Eastern"])
+    tm.assert_series_equal(res, exp)
+
+    # timedelta
+    vals = [pd.Timedelta("1 days"), pd.Timedelta("2 days")]
+    s = Series(vals)
+    assert s.dtype == "timedelta64[ns]"
+    res = s.apply(lambda x: f"{type(x).__name__}_{x.days}")
+    exp = Series(["Timedelta_1", "Timedelta_2"])
+    tm.assert_series_equal(res, exp)
+
+    # period
+    vals = [pd.Period("2011-01-01", freq="M"), pd.Period("2011-01-02", freq="M")]
+    s = Series(vals)
+    assert s.dtype == "Period[M]"
+    res = s.apply(lambda x: f"{type(x).__name__}_{x.freqstr}")
+    exp = Series(["Period_M", "Period_M"])
+    tm.assert_series_equal(res, exp)
+
+
+def test_map_categorical():
+    values = pd.Categorical(list("ABBABCD"), categories=list("DCBA"), ordered=True)
+    s = Series(values, name="XX", index=list("abcdefg"))
+
+    result = s.map(lambda x: x.lower())
+    exp_values = pd.Categorical(list("abbabcd"), categories=list("dcba"), ordered=True)
+    exp = Series(exp_values, name="XX", index=list("abcdefg"))
+    tm.assert_series_equal(result, exp)
+    tm.assert_categorical_equal(result.values, exp_values)
+
+    result = s.map(lambda x: "A")
+    exp = Series(["A"] * 7, name="XX", index=list("abcdefg"))
+    tm.assert_series_equal(result, exp)
+    assert result.dtype == object
+
+
+def test_map_datetimetz():
+    values = pd.date_range("2011-01-01", "2011-01-02", freq="H").tz_localize(
+        "Asia/Tokyo"
+    )
+    s = Series(values, name="XX")
+
+    # keep tz
+    result = s.map(lambda x: x + pd.offsets.Day())
+    exp_values = pd.date_range("2011-01-02", "2011-01-03", freq="H").tz_localize(
+        "Asia/Tokyo"
+    )
+    exp = Series(exp_values, name="XX")
+    tm.assert_series_equal(result, exp)
+
+    # change dtype
+    # GH 14506 : Returned dtype changed from int32 to int64
+    result = s.map(lambda x: x.hour)
+    exp = Series(list(range(24)) + [0], name="XX", dtype=np.int64)
+    tm.assert_series_equal(result, exp)
+
+    # not vectorized
+    def f(x):
+        if not isinstance(x, pd.Timestamp):
+            raise ValueError
+        return str(x.tz)
+
+    result = s.map(f)
+    exp = Series(["Asia/Tokyo"] * 25, name="XX")
+    tm.assert_series_equal(result, exp)
+
+
+@pytest.mark.parametrize(
+    "vals,mapping,exp",
+    [
+        (list("abc"), {np.nan: "not NaN"}, [np.nan] * 3 + ["not NaN"]),
+        (list("abc"), {"a": "a letter"}, ["a letter"] + [np.nan] * 3),
+        (list(range(3)), {0: 42}, [42] + [np.nan] * 3),
+    ],
+)
+def test_map_missing_mixed(vals, mapping, exp):
+    # GH20495
+    s = Series(vals + [np.nan])
+    result = s.map(mapping)
+
+    tm.assert_series_equal(result, Series(exp))
+
+
+@pytest.mark.parametrize(
+    "dti,exp",
+    [
+        (
+            Series([1, 2], index=pd.DatetimeIndex([0, 31536000000])),
+            DataFrame(np.repeat([[1, 2]], 2, axis=0), dtype="int64"),
+        ),
+        (
+            tm.makeTimeSeries(nper=30),
+            DataFrame(np.repeat([[1, 2]], 30, axis=0), dtype="int64"),
+        ),
+    ],
+)
+@pytest.mark.parametrize("aware", [True, False])
+def test_apply_series_on_date_time_index_aware_series(dti, exp, aware):
+    # GH 25959
+    # Calling apply on a localized time series should not cause an error
+    if aware:
+        index = dti.tz_localize("UTC").index
+    else:
+        index = dti.index
+    result = Series(index).apply(lambda x: Series([1, 2]))
+    tm.assert_frame_equal(result, exp)
+
+
+def test_apply_scalar_on_date_time_index_aware_series():
+    # GH 25959
+    # Calling apply on a localized time series should not cause an error
+    series = tm.makeTimeSeries(nper=30).tz_localize("UTC")
+    result = Series(series.index).apply(lambda x: 1)
+    tm.assert_series_equal(result, Series(np.ones(30), dtype="int64"))
+
+
+def test_map_float_to_string_precision():
+    # GH 13228
+    ser = Series(1 / 3)
+    result = ser.map(lambda val: str(val)).to_dict()
+    expected = {0: "0.3333333333333333"}
+    assert result == expected
+
+
+def test_apply_to_timedelta():
+    list_of_valid_strings = ["00:00:01", "00:00:02"]
+    a = pd.to_timedelta(list_of_valid_strings)
+    b = Series(list_of_valid_strings).apply(pd.to_timedelta)
+    tm.assert_series_equal(Series(a), b)
+
+    list_of_strings = ["00:00:01", np.nan, pd.NaT, pd.NaT]
+
+    a = pd.to_timedelta(list_of_strings)
+    with tm.assert_produces_warning(FutureWarning, match="Inferring timedelta64"):
+        ser = Series(list_of_strings)
+    b = ser.apply(pd.to_timedelta)
+    tm.assert_series_equal(Series(a), b)
+
+
+@pytest.mark.parametrize(
+    "ops, names",
+    [
+        ([np.sum], ["sum"]),
+        ([np.sum, np.mean], ["sum", "mean"]),
+        (np.array([np.sum]), ["sum"]),
+        (np.array([np.sum, np.mean]), ["sum", "mean"]),
+    ],
+)
+@pytest.mark.parametrize("how", ["agg", "apply"])
+def test_apply_listlike_reducer(string_series, ops, names, how):
+    # GH 39140
+    expected = Series({name: op(string_series) for name, op in zip(names, ops)})
+    expected.name = "series"
+    result = getattr(string_series, how)(ops)
+    tm.assert_series_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "ops",
+    [
+        {"A": np.sum},
+        {"A": np.sum, "B": np.mean},
+        Series({"A": np.sum}),
+        Series({"A": np.sum, "B": np.mean}),
+    ],
+)
+@pytest.mark.parametrize("how", ["agg", "apply"])
+def test_apply_dictlike_reducer(string_series, ops, how):
+    # GH 39140
+    expected = Series({name: op(string_series) for name, op in ops.items()})
+    expected.name = string_series.name
+    result = getattr(string_series, how)(ops)
+    tm.assert_series_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "ops, names",
+    [
+        ([np.sqrt], ["sqrt"]),
+        ([np.abs, np.sqrt], ["absolute", "sqrt"]),
+        (np.array([np.sqrt]), ["sqrt"]),
+        (np.array([np.abs, np.sqrt]), ["absolute", "sqrt"]),
+    ],
+)
+def test_apply_listlike_transformer(string_series, ops, names):
+    # GH 39140
+    with np.errstate(all="ignore"):
+        expected = concat([op(string_series) for op in ops], axis=1)
+        expected.columns = names
+        result = string_series.apply(ops)
+        tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "ops",
+    [
+        {"A": np.sqrt},
+        {"A": np.sqrt, "B": np.exp},
+        Series({"A": np.sqrt}),
+        Series({"A": np.sqrt, "B": np.exp}),
+    ],
+)
+def test_apply_dictlike_transformer(string_series, ops):
+    # GH 39140
+    with np.errstate(all="ignore"):
+        expected = concat({name: op(string_series) for name, op in ops.items()})
+        expected.name = string_series.name
+        result = string_series.apply(ops)
+        tm.assert_series_equal(result, expected)
+
+
+def test_apply_retains_column_name():
+    # GH 16380
+    df = DataFrame({"x": range(3)}, Index(range(3), name="x"))
+    result = df.x.apply(lambda x: Series(range(x + 1), Index(range(x + 1), name="y")))
+    expected = DataFrame(
+        [[0.0, np.nan, np.nan], [0.0, 1.0, np.nan], [0.0, 1.0, 2.0]],
+        columns=Index(range(3), name="y"),
+        index=Index(range(3), name="x"),
+    )
+    tm.assert_frame_equal(result, expected)

.venv/Lib/site-packages/pandas/tests/apply/test_series_apply_relabeling.py

@@ -0,0 +1,33 @@
+import pandas as pd
+import pandas._testing as tm
+
+
+def test_relabel_no_duplicated_method():
+    # this is to test there is no duplicated method used in agg
+    df = pd.DataFrame({"A": [1, 2, 1, 2], "B": [1, 2, 3, 4]})
+
+    result = df["A"].agg(foo="sum")
+    expected = df["A"].agg({"foo": "sum"})
+    tm.assert_series_equal(result, expected)
+
+    result = df["B"].agg(foo="min", bar="max")
+    expected = df["B"].agg({"foo": "min", "bar": "max"})
+    tm.assert_series_equal(result, expected)
+
+    result = df["B"].agg(foo=sum, bar=min, cat="max")
+    expected = df["B"].agg({"foo": sum, "bar": min, "cat": "max"})
+    tm.assert_series_equal(result, expected)
+
+
+def test_relabel_duplicated_method():
+    # this is to test with nested renaming, duplicated method can be used
+    # if they are assigned with different new names
+    df = pd.DataFrame({"A": [1, 2, 1, 2], "B": [1, 2, 3, 4]})
+
+    result = df["A"].agg(foo="sum", bar="sum")
+    expected = pd.Series([6, 6], index=["foo", "bar"], name="A")
+    tm.assert_series_equal(result, expected)
+
+    result = df["B"].agg(foo=min, bar="min")
+    expected = pd.Series([1, 1], index=["foo", "bar"], name="B")
+    tm.assert_series_equal(result, expected)

.venv/Lib/site-packages/pandas/tests/apply/test_series_transform.py

@@ -0,0 +1,49 @@
+import numpy as np
+import pytest
+
+from pandas import (
+    DataFrame,
+    MultiIndex,
+    Series,
+    concat,
+)
+import pandas._testing as tm
+
+
+@pytest.mark.parametrize(
+    "ops, names",
+    [
+        ([np.sqrt], ["sqrt"]),
+        ([np.abs, np.sqrt], ["absolute", "sqrt"]),
+        (np.array([np.sqrt]), ["sqrt"]),
+        (np.array([np.abs, np.sqrt]), ["absolute", "sqrt"]),
+    ],
+)
+def test_transform_listlike(string_series, ops, names):
+    # GH 35964
+    with np.errstate(all="ignore"):
+        expected = concat([op(string_series) for op in ops], axis=1)
+        expected.columns = names
+        result = string_series.transform(ops)
+        tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize("box", [dict, Series])
+def test_transform_dictlike(string_series, box):
+    # GH 35964
+    with np.errstate(all="ignore"):
+        expected = concat([np.sqrt(string_series), np.abs(string_series)], axis=1)
+    expected.columns = ["foo", "bar"]
+    result = string_series.transform(box({"foo": np.sqrt, "bar": np.abs}))
+    tm.assert_frame_equal(result, expected)
+
+
+def test_transform_dictlike_mixed():
+    # GH 40018 - mix of lists and non-lists in values of a dictionary
+    df = Series([1, 4])
+    result = df.transform({"b": ["sqrt", "abs"], "c": "sqrt"})
+    expected = DataFrame(
+        [[1.0, 1, 1.0], [2.0, 4, 2.0]],
+        columns=MultiIndex([("b", "c"), ("sqrt", "abs")], [(0, 0, 1), (0, 1, 0)]),
+    )
+    tm.assert_frame_equal(result, expected)

.venv/Lib/site-packages/pandas/tests/apply/test_str.py

@@ -0,0 +1,302 @@
+from itertools import chain
+import operator
+
+import numpy as np
+import pytest
+
+from pandas.core.dtypes.common import is_number
+
+from pandas import (
+    DataFrame,
+    Index,
+    Series,
+)
+import pandas._testing as tm
+from pandas.core.groupby.base import maybe_normalize_deprecated_kernels
+from pandas.tests.apply.common import (
+    frame_transform_kernels,
+    series_transform_kernels,
+)
+
+
+@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, True], {"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_with_string_args(datetime_series):
+
+    for arg in ["sum", "mean", "min", "max", "std"]:
+        result = datetime_series.apply(arg)
+        expected = getattr(datetime_series, arg)()
+        assert 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)
+
+
+@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
+
+    # float_frame will _usually_ have negative values, which will
+    #  trigger the warning here, but let's put one in just to be sure
+    float_frame.iloc[0, 0] = -1.0
+    warn = None
+    if op in ["log", "sqrt"]:
+        warn = RuntimeWarning
+
+    with tm.assert_produces_warning(warn):
+        result = getattr(float_frame, how)(op)
+        expected = getattr(np, op)(float_frame)
+    tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "series, func, expected",
+    chain(
+        tm.get_cython_table_params(
+            Series(dtype=np.float64),
+            [
+                ("sum", 0),
+                ("max", np.nan),
+                ("min", np.nan),
+                ("all", True),
+                ("any", False),
+                ("mean", np.nan),
+                ("prod", 1),
+                ("std", np.nan),
+                ("var", np.nan),
+                ("median", np.nan),
+            ],
+        ),
+        tm.get_cython_table_params(
+            Series([np.nan, 1, 2, 3]),
+            [
+                ("sum", 6),
+                ("max", 3),
+                ("min", 1),
+                ("all", True),
+                ("any", True),
+                ("mean", 2),
+                ("prod", 6),
+                ("std", 1),
+                ("var", 1),
+                ("median", 2),
+            ],
+        ),
+        tm.get_cython_table_params(
+            Series("a b c".split()),
+            [
+                ("sum", "abc"),
+                ("max", "c"),
+                ("min", "a"),
+                ("all", True),
+                ("any", True),
+            ],
+        ),
+    ),
+)
+def test_agg_cython_table_series(series, func, expected):
+    # GH21224
+    # test reducing functions in
+    # pandas.core.base.SelectionMixin._cython_table
+    result = series.agg(func)
+    if is_number(expected):
+        assert np.isclose(result, expected, equal_nan=True)
+    else:
+        assert result == expected
+
+
+@pytest.mark.parametrize(
+    "series, func, expected",
+    chain(
+        tm.get_cython_table_params(
+            Series(dtype=np.float64),
+            [
+                ("cumprod", Series([], Index([]), dtype=np.float64)),
+                ("cumsum", Series([], Index([]), dtype=np.float64)),
+            ],
+        ),
+        tm.get_cython_table_params(
+            Series([np.nan, 1, 2, 3]),
+            [
+                ("cumprod", Series([np.nan, 1, 2, 6])),
+                ("cumsum", Series([np.nan, 1, 3, 6])),
+            ],
+        ),
+        tm.get_cython_table_params(
+            Series("a b c".split()), [("cumsum", Series(["a", "ab", "abc"]))]
+        ),
+    ),
+)
+def test_agg_cython_table_transform_series(series, func, expected):
+    # GH21224
+    # test transforming functions in
+    # pandas.core.base.SelectionMixin._cython_table (cumprod, cumsum)
+    result = series.agg(func)
+    tm.assert_series_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_frame(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_frame(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("op", series_transform_kernels)
+def test_transform_groupby_kernel_series(string_series, op):
+    # GH 35964
+    # TODO(2.0) Remove after pad/backfill deprecation enforced
+    op = maybe_normalize_deprecated_kernels(op)
+    args = [0.0] if op == "fillna" else []
+    ones = np.ones(string_series.shape[0])
+    expected = string_series.groupby(ones).transform(op, *args)
+    result = string_series.transform(op, 0, *args)
+    tm.assert_series_equal(result, expected)
+
+
+@pytest.mark.parametrize("op", frame_transform_kernels)
+def test_transform_groupby_kernel_frame(
+    axis, float_frame, op, using_array_manager, request
+):
+    # TODO(2.0) Remove after pad/backfill deprecation enforced
+    op = maybe_normalize_deprecated_kernels(op)
+    # GH 35964
+    if using_array_manager and op == "pct_change" and axis in (1, "columns"):
+        # TODO(ArrayManager) shift with axis=1
+        request.node.add_marker(
+            pytest.mark.xfail(
+                reason="shift axis=1 not yet implemented for ArrayManager"
+            )
+        )
+
+    args = [0.0] if op == "fillna" else []
+    if axis == 0 or axis == "index":
+        ones = np.ones(float_frame.shape[0])
+    else:
+        ones = np.ones(float_frame.shape[1])
+    expected = float_frame.groupby(ones, axis=axis).transform(op, *args)
+    result = float_frame.transform(op, axis, *args)
+    tm.assert_frame_equal(result, expected)
+
+    # same thing, but ensuring we have multiple blocks
+    assert "E" not in float_frame.columns
+    float_frame["E"] = float_frame["A"].copy()
+    assert len(float_frame._mgr.arrays) > 1
+
+    if axis == 0 or axis == "index":
+        ones = np.ones(float_frame.shape[0])
+    else:
+        ones = np.ones(float_frame.shape[1])
+    expected2 = float_frame.groupby(ones, axis=axis).transform(op, *args)
+    result2 = float_frame.transform(op, axis, *args)
+    tm.assert_frame_equal(result2, expected2)
+
+
+@pytest.mark.parametrize("method", ["abs", "shift", "pct_change", "cumsum", "rank"])
+def test_transform_method_name(method):
+    # GH 19760
+    df = DataFrame({"A": [-1, 2]})
+    result = df.transform(method)
+    expected = operator.methodcaller(method)(df)
+    tm.assert_frame_equal(result, expected)