code: from datetime import datetime
  from decimal import Decimal
  from io import StringIO
  
  import numpy as np
  import pytest
  
  from pandas.compat import IS64
  from pandas.errors import PerformanceWarning
  
  import pandas as pd
  from pandas import (
      Categorical,
      DataFrame,
      Grouper,
      Index,
      MultiIndex,
      Series,
      Timestamp,
      date_range,
      read_csv,
      to_datetime,
  )
  import pandas._testing as tm
  from pandas.core.base import SpecificationError
  import pandas.core.common as com
  
  
  def test_repr():
      # GH18203
      result = repr(Grouper(key="A", level="B"))
      expected = "Grouper(key='A', level='B', axis=0, sort=False)"
      assert result == expected
  
  
  @pytest.mark.parametrize("dtype", ["int64", "int32", "float64", "float32"])
  def test_basic(dtype):
  
      data = Series(np.arange(9) // 3, index=np.arange(9), dtype=dtype)
  
      index = np.arange(9)
      np.random.shuffle(index)
      data = data.reindex(index)
  
      grouped = data.groupby(lambda x: x // 3)
  
      for k, v in grouped:
          assert len(v) == 3
  
      agged = grouped.aggregate(np.mean)
      assert agged[1] == 1
  
      tm.assert_series_equal(agged, grouped.agg(np.mean))  # shorthand
      tm.assert_series_equal(agged, grouped.mean())
      tm.assert_series_equal(grouped.agg(np.sum), grouped.sum())
  
      expected = grouped.apply(lambda x: x * x.sum())
      transformed = grouped.transform(lambda x: x * x.sum())
      assert transformed[7] == 12
      tm.assert_series_equal(transformed, expected)
  
      value_grouped = data.groupby(data)
      tm.assert_series_equal(
          value_grouped.aggregate(np.mean), agged, check_index_type=False
      )
  
      # complex agg
      agged = grouped.aggregate([np.mean, np.std])
  
      msg = r"nested renamer is not supported"
      with pytest.raises(SpecificationError, match=msg):
          grouped.aggregate({"one": np.mean, "two": np.std})
  
      group_constants = {0: 10, 1: 20, 2: 30}
      agged = grouped.agg(lambda x: group_constants[x.name] + x.mean())
      assert agged[1] == 21
  
      # corner cases
      msg = "Must produce aggregated value"
      # exception raised is type Exception
      with pytest.raises(Exception, match=msg):
          grouped.aggregate(lambda x: x * 2)
  
  
  def test_groupby_nonobject_dtype(mframe, df_mixed_floats):
      key = mframe.index.codes[0]
      grouped = mframe.groupby(key)
      result = grouped.sum()
  
      expected = mframe.groupby(key.astype("O")).sum()
      tm.assert_frame_equal(result, expected)
  
      # GH 3911, mixed frame non-conversion
      df = df_mixed_floats.copy()
      df["value"] = range(len(df))
  
      def max_value(group):
          return group.loc[group["value"].idxmax()]
  
      applied = df.groupby("A").apply(max_value)
      result = applied.dtypes
      expected = df.dtypes
      tm.assert_series_equal(result, expected)
  
  
  def test_groupby_return_type():
  
      # GH2893, return a reduced type
      df1 = DataFrame(
          [
              {"val1": 1, "val2": 20},
              {"val1": 1, "val2": 19},
              {"val1": 2, "val2": 27},
              {"val1": 2, "val2": 12},
          ]
      )
  
      def func(dataf):
          return dataf["val2"] - dataf["val2"].mean()
  
      with tm.assert_produces_warning(FutureWarning):
          result = df1.groupby("val1", squeeze=True).apply(func)
      assert isinstance(result, Series)
  
      df2 = DataFrame(
          [
              {"val1": 1, "val2": 20},
              {"val1": 1, "val2": 19},
              {"val1": 1, "val2": 27},
              {"val1": 1, "val2": 12},
          ]
      )
  
      def func(dataf):
          return dataf["val2"] - dataf["val2"].mean()
  
      with tm.assert_produces_warning(FutureWarning):
          result = df2.groupby("val1", squeeze=True).apply(func)
      assert isinstance(result, Series)
  
      # GH3596, return a consistent type (regression in 0.11 from 0.10.1)
      df = DataFrame([[1, 1], [1, 1]], columns=["X", "Y"])
      with tm.assert_produces_warning(FutureWarning):
          result = df.groupby("X", squeeze=False).count()
      assert isinstance(result, DataFrame)
  
  
  def test_inconsistent_return_type():
      # GH5592
      # inconsistent return type
      df = DataFrame(
          {
              "A": ["Tiger", "Tiger", "Tiger", "Lamb", "Lamb", "Pony", "Pony"],
              "B": Series(np.arange(7), dtype="int64"),
              "C": date_range("20130101", periods=7),
          }
      )
  
      def f(grp):
          return grp.iloc[0]
  
      expected = df.groupby("A").first()[["B"]]
      result = df.groupby("A").apply(f)[["B"]]
      tm.assert_frame_equal(result, expected)
  
      def f(grp):
          if grp.name == "Tiger":
              return None
          return grp.iloc[0]
  
      result = df.groupby("A").apply(f)[["B"]]
      e = expected.copy()
      e.loc["Tiger"] = np.nan
      tm.assert_frame_equal(result, e)
  
      def f(grp):
          if grp.name == "Pony":
              return None
          return grp.iloc[0]
  
      result = df.groupby("A").apply(f)[["B"]]
      e = expected.copy()
      e.loc["Pony"] = np.nan
      tm.assert_frame_equal(result, e)
  
      # 5592 revisited, with datetimes
      def f(grp):
          if grp.name == "Pony":
              return None
          return grp.iloc[0]
  
      result = df.groupby("A").apply(f)[["C"]]
      e = df.groupby("A").first()[["C"]]
      e.loc["Pony"] = pd.NaT
      tm.assert_frame_equal(result, e)
  
      # scalar outputs
      def f(grp):
          if grp.name == "Pony":
              return None
          return grp.iloc[0].loc["C"]
  
      result = df.groupby("A").apply(f)
      e = df.groupby("A").first()["C"].copy()
      e.loc["Pony"] = np.nan
      e.name = None
      tm.assert_series_equal(result, e)
  
  
  def test_pass_args_kwargs(ts, tsframe):
      def f(x, q=None, axis=0):
          return np.percentile(x, q, axis=axis)
  
      g = lambda x: np.percentile(x, 80, axis=0)
  
      # Series
      ts_grouped = ts.groupby(lambda x: x.month)
      agg_result = ts_grouped.agg(np.percentile, 80, axis=0)
      apply_result = ts_grouped.apply(np.percentile, 80, axis=0)
      trans_result = ts_grouped.transform(np.percentile, 80, axis=0)
  
      agg_expected = ts_grouped.quantile(0.8)
      trans_expected = ts_grouped.transform(g)
  
      tm.assert_series_equal(apply_result, agg_expected)
      tm.assert_series_equal(agg_result, agg_expected)
      tm.assert_series_equal(trans_result, trans_expected)
  
      agg_result = ts_grouped.agg(f, q=80)
      apply_result = ts_grouped.apply(f, q=80)
      trans_result = ts_grouped.transform(f, q=80)
      tm.assert_series_equal(agg_result, agg_expected)
      tm.assert_series_equal(apply_result, agg_expected)
      tm.assert_series_equal(trans_result, trans_expected)
  
      # DataFrame
      df_grouped = tsframe.groupby(lambda x: x.month)
      agg_result = df_grouped.agg(np.percentile, 80, axis=0)
      apply_result = df_grouped.apply(DataFrame.quantile, 0.8)
      expected = df_grouped.quantile(0.8)
      tm.assert_frame_equal(apply_result, expected, check_names=False)
      tm.assert_frame_equal(agg_result, expected)
  
      agg_result = df_grouped.agg(f, q=80)
      apply_result = df_grouped.apply(DataFrame.quantile, q=0.8)
      tm.assert_frame_equal(agg_result, expected)
      tm.assert_frame_equal(apply_result, expected, check_names=False)
  
  
  def test_len():
      df = tm.makeTimeDataFrame()
      grouped = df.groupby([lambda x: x.year, lambda x: x.month, lambda x: x.day])
      assert len(grouped) == len(df)
  
      grouped = df.groupby([lambda x: x.year, lambda x: x.month])
      expected = len({(x.year, x.month) for x in df.index})
      assert len(grouped) == expected
  
      # issue 11016
      df = DataFrame({"a": [np.nan] * 3, "b": [1, 2, 3]})
      assert len(df.groupby("a")) == 0
      assert len(df.groupby("b")) == 3
      assert len(df.groupby(["a", "b"])) == 3
  
  
  def test_basic_regression():
      # regression
      result = Series([1.0 * x for x in list(range(1, 10)) * 10])
  
      data = np.random.random(1100) * 10.0
      groupings = Series(data)
  
      grouped = result.groupby(groupings)
      grouped.mean()
  
  
  @pytest.mark.parametrize(
      "dtype", ["float64", "float32", "int64", "int32", "int16", "int8"]
  )
  def test_with_na_groups(dtype):
      index = Index(np.arange(10))
      values = Series(np.ones(10), index, dtype=dtype)
      labels = Series(
          [np.nan, "foo", "bar", "bar", np.nan, np.nan, "bar", "bar", np.nan, "foo"],
          index=index,
      )
  
      # this SHOULD be an int
      grouped = values.groupby(labels)
      agged = grouped.agg(len)
      expected = Series([4, 2], index=["bar", "foo"])
  
      tm.assert_series_equal(agged, expected, check_dtype=False)
  
      # assert issubclass(agged.dtype.type, np.integer)
  
      # explicitly return a float from my function
      def f(x):
          return float(len(x))
  
      agged = grouped.agg(f)
      expected = Series([4.0, 2.0], index=["bar", "foo"])
  
      tm.assert_series_equal(agged, expected)
  
  
  def test_indices_concatenation_order():
  
      # GH 2808
  
      def f1(x):
          y = x[(x.b % 2) == 1] ** 2
          if y.empty:
              multiindex = MultiIndex(levels=[[]] * 2, codes=[[]] * 2, names=["b", "c"])
              res = DataFrame(columns=["a"], index=multiindex)
              return res
          else:
              y = y.set_index(["b", "c"])
              return y
  
      def f2(x):
          y = x[(x.b % 2) == 1] ** 2
          if y.empty:
              return DataFrame()
          else:
              y = y.set_index(["b", "c"])
              return y
  
      def f3(x):
          y = x[(x.b % 2) == 1] ** 2
          if y.empty:
              multiindex = MultiIndex(
                  levels=[[]] * 2, codes=[[]] * 2, names=["foo", "bar"]
              )
              res = DataFrame(columns=["a", "b"], index=multiindex)
              return res
          else:
              return y
  
      df = DataFrame({"a": [1, 2, 2, 2], "b": range(4), "c": range(5, 9)})
  
      df2 = DataFrame({"a": [3, 2, 2, 2], "b": range(4), "c": range(5, 9)})
  
      # correct result
      result1 = df.groupby("a").apply(f1)
      result2 = df2.groupby("a").apply(f1)
      tm.assert_frame_equal(result1, result2)
  
      # should fail (not the same number of levels)
      msg = "Cannot concat indices that do not have the same number of levels"
      with pytest.raises(AssertionError, match=msg):
          df.groupby("a").apply(f2)
      with pytest.raises(AssertionError, match=msg):
          df2.groupby("a").apply(f2)
  
      # should fail (incorrect shape)
      with pytest.raises(AssertionError, match=msg):
          df.groupby("a").apply(f3)
      with pytest.raises(AssertionError, match=msg):
          df2.groupby("a").apply(f3)
  
  
  def test_attr_wrapper(ts):
      grouped = ts.groupby(lambda x: x.weekday())
  
      result = grouped.std()
      expected = grouped.agg(lambda x: np.std(x, ddof=1))
      tm.assert_series_equal(result, expected)
  
      # this is pretty cool
      result = grouped.describe()
      expected = {name: gp.describe() for name, gp in grouped}
      expected = DataFrame(expected).T
      tm.assert_frame_equal(result, expected)
  
      # get attribute
      result = grouped.dtype
      expected = grouped.agg(lambda x: x.dtype)
      tm.assert_series_equal(result, expected)
  
      # make sure raises error
      msg = "'SeriesGroupBy' object has no attribute 'foo'"
      with pytest.raises(AttributeError, match=msg):
          getattr(grouped, "foo")
  
  
  def test_frame_groupby(tsframe):
      grouped = tsframe.groupby(lambda x: x.weekday())
  
      # aggregate
      aggregated = grouped.aggregate(np.mean)
      assert len(aggregated) == 5
      assert len(aggregated.columns) == 4
  
      # by string
      tscopy = tsframe.copy()
      tscopy["weekday"] = [x.weekday() for x in tscopy.index]
      stragged = tscopy.groupby("weekday").aggregate(np.mean)
      tm.assert_frame_equal(stragged, aggregated, check_names=False)
  
      # transform
      grouped = tsframe.head(30).groupby(lambda x: x.weekday())
      transformed = grouped.transform(lambda x: x - x.mean())
      assert len(transformed) == 30
      assert len(transformed.columns) == 4
  
      # transform propagate
      transformed = grouped.transform(lambda x: x.mean())
      for name, group in grouped:
          mean = group.mean()
          for idx in group.index:
              tm.assert_series_equal(transformed.xs(idx), mean, check_names=False)
  
      # iterate
      for weekday, group in grouped:
          assert group.index[0].weekday() == weekday
  
      # groups / group_indices
      groups = grouped.groups
      indices = grouped.indices
  
      for k, v in groups.items():
          samething = tsframe.index.take(indices[k])
          assert (samething == v).all()
  
  
  def test_frame_groupby_columns(tsframe):
      mapping = {"A": 0, "B": 0, "C": 1, "D": 1}
      grouped = tsframe.groupby(mapping, axis=1)
  
      # aggregate
      aggregated = grouped.aggregate(np.mean)
      assert len(aggregated) == len(tsframe)
      assert len(aggregated.columns) == 2
  
      # transform
      tf = lambda x: x - x.mean()
      groupedT = tsframe.T.groupby(mapping, axis=0)
      tm.assert_frame_equal(groupedT.transform(tf).T, grouped.transform(tf))
  
      # iterate
      for k, v in grouped:
          assert len(v.columns) == 2
  
  
  def test_frame_set_name_single(df):
      grouped = df.groupby("A")
  
      result = grouped.mean()
      assert result.index.name == "A"
  
      result = df.groupby("A", as_index=False).mean()
      assert result.index.name != "A"
  
      result = grouped.agg(np.mean)
      assert result.index.name == "A"
  
      result = grouped.agg({"C": np.mean, "D": np.std})
      assert result.index.name == "A"
  
      result = grouped["C"].mean()
      assert result.index.name == "A"
      result = grouped["C"].agg(np.mean)
      assert result.index.name == "A"
      result = grouped["C"].agg([np.mean, np.std])
      assert result.index.name == "A"
  
      msg = r"nested renamer is not supported"
      with pytest.raises(SpecificationError, match=msg):
          grouped["C"].agg({"foo": np.mean, "bar": np.std})
  
  
  def test_multi_func(df):
      col1 = df["A"]
      col2 = df["B"]
  
      grouped = df.groupby([col1.get, col2.get])
      agged = grouped.mean()
      expected = df.groupby(["A", "B"]).mean()
  
      # TODO groupby get drops names
      tm.assert_frame_equal(
          agged.loc[:, ["C", "D"]], expected.loc[:, ["C", "D"]], check_names=False
      )
  
      # some "groups" with no data
      df = DataFrame(
          {
              "v1": np.random.randn(6),
              "v2": np.random.randn(6),
              "k1": np.array(["b", "b", "b", "a", "a", "a"]),
              "k2": np.array(["1", "1", "1", "2", "2", "2"]),
          },
          index=["one", "two", "three", "four", "five", "six"],
      )
      # only verify that it works for now
      grouped = df.groupby(["k1", "k2"])
      grouped.agg(np.sum)
  
  
  def test_multi_key_multiple_functions(df):
      grouped = df.groupby(["A", "B"])["C"]
  
      agged = grouped.agg([np.mean, np.std])
      expected = DataFrame({"mean": grouped.agg(np.mean), "std": grouped.agg(np.std)})
      tm.assert_frame_equal(agged, expected)
  
  
  def test_frame_multi_key_function_list():
      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),
          }
      )
  
      grouped = data.groupby(["A", "B"])
      funcs = [np.mean, np.std]
      agged = grouped.agg(funcs)
      expected = pd.concat(
          [grouped["D"].agg(funcs), grouped["E"].agg(funcs), grouped["F"].agg(funcs)],
          keys=["D", "E", "F"],
          axis=1,
      )
      assert isinstance(agged.index, MultiIndex)
      assert isinstance(expected.index, MultiIndex)
      tm.assert_frame_equal(agged, expected)
  
  
  @pytest.mark.parametrize("op", [lambda x: x.sum(), lambda x: x.mean()])
  def test_groupby_multiple_columns(df, op):
      data = df
      grouped = data.groupby(["A", "B"])
  
      result1 = op(grouped)
  
      keys = []
      values = []
      for n1, gp1 in data.groupby("A"):
          for n2, gp2 in gp1.groupby("B"):
              keys.append((n1, n2))
              values.append(op(gp2.loc[:, ["C", "D"]]))
  
      mi = MultiIndex.from_tuples(keys, names=["A", "B"])
      expected = pd.concat(values, axis=1).T
      expected.index = mi
  
      # a little bit crude
      for col in ["C", "D"]:
          result_col = op(grouped[col])
          pivoted = result1[col]
          exp = expected[col]
          tm.assert_series_equal(result_col, exp)
          tm.assert_series_equal(pivoted, exp)
  
      # test single series works the same
      result = data["C"].groupby([data["A"], data["B"]]).mean()
      expected = data.groupby(["A", "B"]).mean()["C"]
  
      tm.assert_series_equal(result, expected)
  
  
  def test_as_index_select_column():
      # GH 5764
      df = DataFrame([[1, 2], [1, 4], [5, 6]], columns=["A", "B"])
      result = df.groupby("A", as_index=False)["B"].get_group(1)
      expected = Series([2, 4], name="B")
      tm.assert_series_equal(result, expected)
  
      result = df.groupby("A", as_index=False)["B"].apply(lambda x: x.cumsum())
      expected = Series(
          [2, 6, 6], name="B", index=MultiIndex.from_tuples([(0, 0), (0, 1), (1, 2)])
      )
      tm.assert_series_equal(result, expected)
  
  
  def test_groupby_as_index_select_column_sum_empty_df():
      # GH 35246
      df = DataFrame(columns=["A", "B", "C"])
      left = df.groupby(by="A", as_index=False)["B"].sum()
      assert type(left) is DataFrame
      assert left.to_dict() == {"A": {}, "B": {}}
  
  
  def test_groupby_as_index_agg(df):
      grouped = df.groupby("A", as_index=False)
  
      # single-key
  
      result = grouped.agg(np.mean)
      expected = grouped.mean()
      tm.assert_frame_equal(result, expected)
  
      result2 = grouped.agg({"C": np.mean, "D": np.sum})
      expected2 = grouped.mean()
      expected2["D"] = grouped.sum()["D"]
      tm.assert_frame_equal(result2, expected2)
  
      grouped = df.groupby("A", as_index=True)
  
      msg = r"nested renamer is not supported"
      with pytest.raises(SpecificationError, match=msg):
          grouped["C"].agg({"Q": np.sum})
  
      # multi-key
  
      grouped = df.groupby(["A", "B"], as_index=False)
  
      result = grouped.agg(np.mean)
      expected = grouped.mean()
      tm.assert_frame_equal(result, expected)
  
      result2 = grouped.agg({"C": np.mean, "D": np.sum})
      expected2 = grouped.mean()
      expected2["D"] = grouped.sum()["D"]
      tm.assert_frame_equal(result2, expected2)
  
      expected3 = grouped["C"].sum()
      expected3 = DataFrame(expected3).rename(columns={"C": "Q"})
      result3 = grouped["C"].agg({"Q": np.sum})
      tm.assert_frame_equal(result3, expected3)
  
      # GH7115 & GH8112 & GH8582
      df = DataFrame(np.random.randint(0, 100, (50, 3)), columns=["jim", "joe", "jolie"])
      ts = Series(np.random.randint(5, 10, 50), name="jim")
  
      gr = df.groupby(ts)
      gr.nth(0)  # invokes set_selection_from_grouper internally
      tm.assert_frame_equal(gr.apply(sum), df.groupby(ts).apply(sum))
  
      for attr in ["mean", "max", "count", "idxmax", "cumsum", "all"]:
          gr = df.groupby(ts, as_index=False)
          left = getattr(gr, attr)()
  
          gr = df.groupby(ts.values, as_index=True)
          right = getattr(gr, attr)().reset_index(drop=True)
  
          tm.assert_frame_equal(left, right)
  
  
  def test_ops_not_as_index(reduction_func):
      # GH 10355, 21090
      # Using as_index=False should not modify grouped column
  
      if reduction_func in ("corrwith",):
          pytest.skip("Test not applicable")
  
      if reduction_func in ("nth", "ngroup"):
          pytest.skip("Skip until behavior is determined (GH #5755)")
  
      df = DataFrame(np.random.randint(0, 5, size=(100, 2)), columns=["a", "b"])
      expected = getattr(df.groupby("a"), reduction_func)()
      if reduction_func == "size":
          expected = expected.rename("size")
      expected = expected.reset_index()
  
      g = df.groupby("a", as_index=False)
  
      result = getattr(g, reduction_func)()
      tm.assert_frame_equal(result, expected)
  
      result = g.agg(reduction_func)
      tm.assert_frame_equal(result, expected)
  
      result = getattr(g["b"], reduction_func)()
      tm.assert_frame_equal(result, expected)
  
      result = g["b"].agg(reduction_func)
      tm.assert_frame_equal(result, expected)
  
  
  def test_as_index_series_return_frame(df):
      grouped = df.groupby("A", as_index=False)
      grouped2 = df.groupby(["A", "B"], as_index=False)
  
      result = grouped["C"].agg(np.sum)
      expected = grouped.agg(np.sum).loc[:, ["A", "C"]]
      assert isinstance(result, DataFrame)
      tm.assert_frame_equal(result, expected)
  
      result2 = grouped2["C"].agg(np.sum)
      expected2 = grouped2.agg(np.sum).loc[:, ["A", "B", "C"]]
      assert isinstance(result2, DataFrame)
      tm.assert_frame_equal(result2, expected2)
  
      result = grouped["C"].sum()
      expected = grouped.sum().loc[:, ["A", "C"]]
      assert isinstance(result, DataFrame)
      tm.assert_frame_equal(result, expected)
  
      result2 = grouped2["C"].sum()
      expected2 = grouped2.sum().loc[:, ["A", "B", "C"]]
      assert isinstance(result2, DataFrame)
      tm.assert_frame_equal(result2, expected2)
  
  
  def test_as_index_series_column_slice_raises(df):
      # GH15072
      grouped = df.groupby("A", as_index=False)
      msg = r"Column\(s\) C already selected"
  
      with pytest.raises(IndexError, match=msg):
          grouped["C"].__getitem__("D")
  
  
  def test_groupby_as_index_cython(df):
      data = df
  
      # single-key
      grouped = data.groupby("A", as_index=False)
      result = grouped.mean()
      expected = data.groupby(["A"]).mean()
      expected.insert(0, "A", expected.index)
      expected.index = np.arange(len(expected))
      tm.assert_frame_equal(result, expected)
  
      # multi-key
      grouped = data.groupby(["A", "B"], as_index=False)
      result = grouped.mean()
      expected = data.groupby(["A", "B"]).mean()
  
      arrays = list(zip(*expected.index.values))
      expected.insert(0, "A", arrays[0])
      expected.insert(1, "B", arrays[1])
      expected.index = np.arange(len(expected))
      tm.assert_frame_equal(result, expected)
  
  
  def test_groupby_as_index_series_scalar(df):
      grouped = df.groupby(["A", "B"], as_index=False)
  
      # GH #421
  
      result = grouped["C"].agg(len)
      expected = grouped.agg(len).loc[:, ["A", "B", "C"]]
      tm.assert_frame_equal(result, expected)
  
  
  def test_groupby_as_index_corner(df, ts):
      msg = "as_index=False only valid with DataFrame"
      with pytest.raises(TypeError, match=msg):
          ts.groupby(lambda x: x.weekday(), as_index=False)
  
      msg = "as_index=False only valid for axis=0"
      with pytest.raises(ValueError, match=msg):
          df.groupby(lambda x: x.lower(), as_index=False, axis=1)
  
  
  def test_groupby_multiple_key(df):
      df = tm.makeTimeDataFrame()
      grouped = df.groupby([lambda x: x.year, lambda x: x.month, lambda x: x.day])
      agged = grouped.sum()
      tm.assert_almost_equal(df.values, agged.values)
  
      grouped = df.T.groupby(
          [lambda x: x.year, lambda x: x.month, lambda x: x.day], axis=1
      )
  
      agged = grouped.agg(lambda x: x.sum())
      tm.assert_index_equal(agged.index, df.columns)
      tm.assert_almost_equal(df.T.values, agged.values)
  
      agged = grouped.agg(lambda x: x.sum())
      tm.assert_almost_equal(df.T.values, agged.values)
  
  
  def test_groupby_multi_corner(df):
      # test that having an all-NA column doesn't mess you up
      df = df.copy()
      df["bad"] = np.nan
      agged = df.groupby(["A", "B"]).mean()
  
      expected = df.groupby(["A", "B"]).mean()
      expected["bad"] = np.nan
  
      tm.assert_frame_equal(agged, expected)
  
  
  def test_omit_nuisance(df):
      grouped = df.groupby("A")
  
      result = grouped.mean()
      expected = df.loc[:, ["A", "C", "D"]].groupby("A").mean()
      tm.assert_frame_equal(result, expected)
  
      agged = grouped.agg(np.mean)
      exp = grouped.mean()
      tm.assert_frame_equal(agged, exp)
  
      df = df.loc[:, ["A", "C", "D"]]
      df["E"] = datetime.now()
      grouped = df.groupby("A")
      result = grouped.agg(np.sum)
      expected = grouped.sum()
      tm.assert_frame_equal(result, expected)
  
      # won't work with axis = 1
      grouped = df.groupby({"A": 0, "C": 0, "D": 1, "E": 1}, axis=1)
      msg = "'DatetimeArray' does not implement reduction 'sum'"
      with pytest.raises(TypeError, match=msg):
          grouped.agg(lambda x: x.sum(0, numeric_only=False))
  
  
  def test_omit_nuisance_sem(df):
      # GH 38774 - sem should work with nuisance columns
      grouped = df.groupby("A")
      result = grouped.sem()
      expected = df.loc[:, ["A", "C", "D"]].groupby("A").sem()
      tm.assert_frame_equal(result, expected)
  
  
  def test_omit_nuisance_python_multiple(three_group):
      grouped = three_group.groupby(["A", "B"])
  
      agged = grouped.agg(np.mean)
      exp = grouped.mean()
      tm.assert_frame_equal(agged, exp)
  
  
  def test_empty_groups_corner(mframe):
      # handle empty groups
      df = DataFrame(
          {
              "k1": np.array(["b", "b", "b", "a", "a", "a"]),
              "k2": np.array(["1", "1", "1", "2", "2", "2"]),
              "k3": ["foo", "bar"] * 3,
              "v1": np.random.randn(6),
              "v2": np.random.randn(6),
          }
      )
  
      grouped = df.groupby(["k1", "k2"])
      result = grouped.agg(np.mean)
      expected = grouped.mean()
      tm.assert_frame_equal(result, expected)
  
      grouped = mframe[3:5].groupby(level=0)
      agged = grouped.apply(lambda x: x.mean())
      agged_A = grouped["A"].apply(np.mean)
      tm.assert_series_equal(agged["A"], agged_A)
      assert agged.index.name == "first"
  
  
  def test_nonsense_func():
      df = DataFrame([0])
      msg = r"unsupported operand type\(s\) for \+: 'int' and 'str'"
      with pytest.raises(TypeError, match=msg):
          df.groupby(lambda x: x + "foo")
  
  
  def test_wrap_aggregated_output_multindex(mframe):
      df = mframe.T
      df["baz", "two"] = "peekaboo"
  
      keys = [np.array([0, 0, 1]), np.array([0, 0, 1])]
      agged = df.groupby(keys).agg(np.mean)
      assert isinstance(agged.columns, MultiIndex)
  
      def aggfun(ser):
          if ser.name == ("foo", "one"):
              raise TypeError
          else:
              return ser.sum()
  
      agged2 = df.groupby(keys).aggregate(aggfun)
      assert len(agged2.columns) + 1 == len(df.columns)
  
  
  def test_groupby_level_apply(mframe):
  
      result = mframe.groupby(level=0).count()
      assert result.index.name == "first"
      result = mframe.groupby(level=1).count()
      assert result.index.name == "second"
  
      result = mframe["A"].groupby(level=0).count()
      assert result.index.name == "first"
  
  
  def test_groupby_level_mapper(mframe):
      deleveled = mframe.reset_index()
  
      mapper0 = {"foo": 0, "bar": 0, "baz": 1, "qux": 1}
      mapper1 = {"one": 0, "two": 0, "three": 1}
  
      result0 = mframe.groupby(mapper0, level=0).sum()
      result1 = mframe.groupby(mapper1, level=1).sum()
  
      mapped_level0 = np.array([mapper0.get(x) for x in deleveled["first"]])
      mapped_level1 = np.array([mapper1.get(x) for x in deleveled["second"]])
      expected0 = mframe.groupby(mapped_level0).sum()
      expected1 = mframe.groupby(mapped_level1).sum()
      expected0.index.name, expected1.index.name = "first", "second"
  
      tm.assert_frame_equal(result0, expected0)
      tm.assert_frame_equal(result1, expected1)
  
  
  def test_groupby_level_nonmulti():
      # GH 1313, GH 13901
      s = Series([1, 2, 3, 10, 4, 5, 20, 6], Index([1, 2, 3, 1, 4, 5, 2, 6], name="foo"))
      expected = Series([11, 22, 3, 4, 5, 6], Index(range(1, 7), name="foo"))
  
      result = s.groupby(level=0).sum()
      tm.assert_series_equal(result, expected)
      result = s.groupby(level=[0]).sum()
      tm.assert_series_equal(result, expected)
      result = s.groupby(level=-1).sum()
      tm.assert_series_equal(result, expected)
      result = s.groupby(level=[-1]).sum()
      tm.assert_series_equal(result, expected)
  
      msg = "level > 0 or level < -1 only valid with MultiIndex"
      with pytest.raises(ValueError, match=msg):
          s.groupby(level=1)
      with pytest.raises(ValueError, match=msg):
          s.groupby(level=-2)
      msg = "No group keys passed!"
      with pytest.raises(ValueError, match=msg):
          s.groupby(level=[])
      msg = "multiple levels only valid with MultiIndex"
      with pytest.raises(ValueError, match=msg):
          s.groupby(level=[0, 0])
      with pytest.raises(ValueError, match=msg):
          s.groupby(level=[0, 1])
      msg = "level > 0 or level < -1 only valid with MultiIndex"
      with pytest.raises(ValueError, match=msg):
          s.groupby(level=[1])
  
  
  def test_groupby_complex():
      # GH 12902
      a = Series(data=np.arange(4) * (1 + 2j), index=[0, 0, 1, 1])
      expected = Series((1 + 2j, 5 + 10j))
  
      result = a.groupby(level=0).sum()
      tm.assert_series_equal(result, expected)
  
      with tm.assert_produces_warning(FutureWarning):
          result = a.sum(level=0)
      tm.assert_series_equal(result, expected)
  
  
  def test_groupby_series_indexed_differently():
      s1 = Series(
          [5.0, -9.0, 4.0, 100.0, -5.0, 55.0, 6.7],
          index=Index(["a", "b", "c", "d", "e", "f", "g"]),
      )
      s2 = Series(
          [1.0, 1.0, 4.0, 5.0, 5.0, 7.0], index=Index(["a", "b", "d", "f", "g", "h"])
      )
  
      grouped = s1.groupby(s2)
      agged = grouped.mean()
      exp = s1.groupby(s2.reindex(s1.index).get).mean()
      tm.assert_series_equal(agged, exp)
  
  
  def test_groupby_with_hier_columns():
      tuples = list(
          zip(
              *[
                  ["bar", "bar", "baz", "baz", "foo", "foo", "qux", "qux"],
                  ["one", "two", "one", "two", "one", "two", "one", "two"],
              ]
          )
      )
      index = MultiIndex.from_tuples(tuples)
      columns = MultiIndex.from_tuples(
          [("A", "cat"), ("B", "dog"), ("B", "cat"), ("A", "dog")]
      )
      df = DataFrame(np.random.randn(8, 4), index=index, columns=columns)
  
      result = df.groupby(level=0).mean()
      tm.assert_index_equal(result.columns, columns)
  
      result = df.groupby(level=0, axis=1).mean()
      tm.assert_index_equal(result.index, df.index)
  
      result = df.groupby(level=0).agg(np.mean)
      tm.assert_index_equal(result.columns, columns)
  
      result = df.groupby(level=0).apply(lambda x: x.mean())
      tm.assert_index_equal(result.columns, columns)
  
      result = df.groupby(level=0, axis=1).agg(lambda x: x.mean(1))
      tm.assert_index_equal(result.columns, Index(["A", "B"]))
      tm.assert_index_equal(result.index, df.index)
  
      # add a nuisance column
      sorted_columns, _ = columns.sortlevel(0)
      df["A", "foo"] = "bar"
      result = df.groupby(level=0).mean()
      tm.assert_index_equal(result.columns, df.columns[:-1])
  
  
  def test_grouping_ndarray(df):
      grouped = df.groupby(df["A"].values)
  
      result = grouped.sum()
      expected = df.groupby("A").sum()
      tm.assert_frame_equal(
          result, expected, check_names=False
      )  # Note: no names when grouping by value
  
  
  def test_groupby_wrong_multi_labels():
      data = """index,foo,bar,baz,spam,data
  0,foo1,bar1,baz1,spam2,20
  1,foo1,bar2,baz1,spam3,30
  2,foo2,bar2,baz1,spam2,40
  3,foo1,bar1,baz2,spam1,50
  4,foo3,bar1,baz2,spam1,60"""
  
      data = read_csv(StringIO(data), index_col=0)
  
      grouped = data.groupby(["foo", "bar", "baz", "spam"])
  
      result = grouped.agg(np.mean)
      expected = grouped.mean()
      tm.assert_frame_equal(result, expected)
  
  
  def test_groupby_series_with_name(df):
      result = df.groupby(df["A"]).mean()
      result2 = df.groupby(df["A"], as_index=False).mean()
      assert result.index.name == "A"
      assert "A" in result2
  
      result = df.groupby([df["A"], df["B"]]).mean()
      result2 = df.groupby([df["A"], df["B"]], as_index=False).mean()
      assert result.index.names == ("A", "B")
      assert "A" in result2
      assert "B" in result2
  
  
  def test_seriesgroupby_name_attr(df):
      # GH 6265
      result = df.groupby("A")["C"]
      assert result.count().name == "C"
      assert result.mean().name == "C"
  
      testFunc = lambda x: np.sum(x) * 2
      assert result.agg(testFunc).name == "C"
  
  
  def test_consistency_name():
      # GH 12363
  
      df = DataFrame(
          {
              "A": ["foo", "bar", "foo", "bar", "foo", "bar", "foo", "foo"],
              "B": ["one", "one", "two", "two", "two", "two", "one", "two"],
              "C": np.random.randn(8) + 1.0,
              "D": np.arange(8),
          }
      )
  
      expected = df.groupby(["A"]).B.count()
      result = df.B.groupby(df.A).count()
      tm.assert_series_equal(result, expected)
  
  
  def test_groupby_name_propagation(df):
      # GH 6124
      def summarize(df, name=None):
          return Series({"count": 1, "mean": 2, "omissions": 3}, name=name)
  
      def summarize_random_name(df):
          # Provide a different name for each Series.  In this case, groupby
          # should not attempt to propagate the Series name since they are
          # inconsistent.
          return Series({"count": 1, "mean": 2, "omissions": 3}, name=df.iloc[0]["A"])
  
      metrics = df.groupby("A").apply(summarize)
      assert metrics.columns.name is None
      metrics = df.groupby("A").apply(summarize, "metrics")
      assert metrics.columns.name == "metrics"
      metrics = df.groupby("A").apply(summarize_random_name)
      assert metrics.columns.name is None
  
  
  def test_groupby_nonstring_columns():
      df = DataFrame([np.arange(10) for x in range(10)])
      grouped = df.groupby(0)
      result = grouped.mean()
      expected = df.groupby(df[0]).mean()
      tm.assert_frame_equal(result, expected)
  
  
  def test_groupby_mixed_type_columns():
      # GH 13432, unorderable types in py3
      df = DataFrame([[0, 1, 2]], columns=["A", "B", 0])
      expected = DataFrame([[1, 2]], columns=["B", 0], index=Index([0], name="A"))
  
      result = df.groupby("A").first()
      tm.assert_frame_equal(result, expected)
  
      result = df.groupby("A").sum()
      tm.assert_frame_equal(result, expected)
  
  
  # TODO: Ensure warning isn't emitted in the first place
  @pytest.mark.filterwarnings("ignore:Mean of:RuntimeWarning")
  def test_cython_grouper_series_bug_noncontig():
      arr = np.empty((100, 100))
      arr.fill(np.nan)
      obj = Series(arr[:, 0])
      inds = np.tile(range(10), 10)
  
      result = obj.groupby(inds).agg(Series.median)
      assert result.isna().all()
  
  
  def test_series_grouper_noncontig_index():
      index = Index(tm.rands_array(10, 100))
  
      values = Series(np.random.randn(50), index=index[::2])
      labels = np.random.randint(0, 5, 50)
  
      # it works!
      grouped = values.groupby(labels)
  
      # accessing the index elements causes segfault
      f = lambda x: len(set(map(id, x.index)))
      grouped.agg(f)
  
  
  def test_convert_objects_leave_decimal_alone():
  
      s = Series(range(5))
      labels = np.array(["a", "b", "c", "d", "e"], dtype="O")
  
      def convert_fast(x):
          return Decimal(str(x.mean()))
  
      def convert_force_pure(x):
          # base will be length 0
          assert len(x.values.base) > 0
          return Decimal(str(x.mean()))
  
      grouped = s.groupby(labels)
  
      result = grouped.agg(convert_fast)
      assert result.dtype == np.object_
      assert isinstance(result[0], Decimal)
  
      result = grouped.agg(convert_force_pure)
      assert result.dtype == np.object_
      assert isinstance(result[0], Decimal)
  
  
  def test_groupby_dtype_inference_empty():
      # GH 6733
      df = DataFrame({"x": [], "range": np.arange(0, dtype="int64")})
      assert df["x"].dtype == np.float64
  
      result = df.groupby("x").first()
      exp_index = Index([], name="x", dtype=np.float64)
      expected = DataFrame({"range": Series([], index=exp_index, dtype="int64")})
      tm.assert_frame_equal(result, expected, by_blocks=True)
  
  
  def test_groupby_unit64_float_conversion():
      #  GH: 30859 groupby converts unit64 to floats sometimes
      df = DataFrame({"first": [1], "second": [1], "value": [16148277970000000000]})
      result = df.groupby(["first", "second"])["value"].max()
      expected = Series(
          [16148277970000000000],
          MultiIndex.from_product([[1], [1]], names=["first", "second"]),
          name="value",
      )
      tm.assert_series_equal(result, expected)
  
  
  def test_groupby_list_infer_array_like(df):
      result = df.groupby(list(df["A"])).mean()
      expected = df.groupby(df["A"]).mean()
      tm.assert_frame_equal(result, expected, check_names=False)
  
      with pytest.raises(KeyError, match=r"^'foo'$"):
          df.groupby(list(df["A"][:-1]))
  
      # pathological case of ambiguity
      df = DataFrame({"foo": [0, 1], "bar": [3, 4], "val": np.random.randn(2)})
  
      result = df.groupby(["foo", "bar"]).mean()
      expected = df.groupby([df["foo"], df["bar"]]).mean()[["val"]]
  
  
  def test_groupby_keys_same_size_as_index():
      # GH 11185
      freq = "s"
      index = date_range(
          start=Timestamp("2015-09-29T11:34:44-0700"), periods=2, freq=freq
      )
      df = DataFrame([["A", 10], ["B", 15]], columns=["metric", "values"], index=index)
      result = df.groupby([Grouper(level=0, freq=freq), "metric"]).mean()
      expected = df.set_index([df.index, "metric"])
  
      tm.assert_frame_equal(result, expected)
  
  
  def test_groupby_one_row():
      # GH 11741
      msg = r"^'Z'$"
      df1 = DataFrame(np.random.randn(1, 4), columns=list("ABCD"))
      with pytest.raises(KeyError, match=msg):
          df1.groupby("Z")
      df2 = DataFrame(np.random.randn(2, 4), columns=list("ABCD"))
      with pytest.raises(KeyError, match=msg):
          df2.groupby("Z")
  
  
  def test_groupby_nat_exclude():
      # GH 6992
      df = DataFrame(
          {
              "values": np.random.randn(8),
              "dt": [
                  np.nan,
                  Timestamp("2013-01-01"),
                  np.nan,
                  Timestamp("2013-02-01"),
                  np.nan,
                  Timestamp("2013-02-01"),
                  np.nan,
                  Timestamp("2013-01-01"),
              ],
              "str": [np.nan, "a", np.nan, "a", np.nan, "a", np.nan, "b"],
          }
      )
      grouped = df.groupby("dt")
  
      expected = [Index([1, 7]), Index([3, 5])]
      keys = sorted(grouped.groups.keys())
      assert len(keys) == 2
      for k, e in zip(keys, expected):
          # grouped.groups keys are np.datetime64 with system tz
          # not to be affected by tz, only compare values
          tm.assert_index_equal(grouped.groups[k], e)
  
      # confirm obj is not filtered
      tm.assert_frame_equal(grouped.grouper.groupings[0].obj, df)
      assert grouped.ngroups == 2
  
      expected = {
          Timestamp("2013-01-01 00:00:00"): np.array([1, 7], dtype=np.intp),
          Timestamp("2013-02-01 00:00:00"): np.array([3, 5], dtype=np.intp),
      }
  
      for k in grouped.indices:
          tm.assert_numpy_array_equal(grouped.indices[k], expected[k])
  
      tm.assert_frame_equal(grouped.get_group(Timestamp("2013-01-01")), df.iloc[[1, 7]])
      tm.assert_frame_equal(grouped.get_group(Timestamp("2013-02-01")), df.iloc[[3, 5]])
  
      with pytest.raises(KeyError, match=r"^NaT$"):
          grouped.get_group(pd.NaT)
  
      nan_df = DataFrame(
          {"nan": [np.nan, np.nan, np.nan], "nat": [pd.NaT, pd.NaT, pd.NaT]}
      )
      assert nan_df["nan"].dtype == "float64"
      assert nan_df["nat"].dtype == "datetime64[ns]"
  
      for key in ["nan", "nat"]:
          grouped = nan_df.groupby(key)
          assert grouped.groups == {}
          assert grouped.ngroups == 0
          assert grouped.indices == {}
          with pytest.raises(KeyError, match=r"^nan$"):
              grouped.get_group(np.nan)
          with pytest.raises(KeyError, match=r"^NaT$"):
              grouped.get_group(pd.NaT)
  
  
  def test_groupby_two_group_keys_all_nan():
      # GH #36842: Grouping over two group keys shouldn't raise an error
      df = DataFrame({"a": [np.nan, np.nan], "b": [np.nan, np.nan], "c": [1, 2]})
      result = df.groupby(["a", "b"]).indices
      assert result == {}
  
  
  def test_groupby_2d_malformed():
      d = DataFrame(index=range(2))
      d["group"] = ["g1", "g2"]
      d["zeros"] = [0, 0]
      d["ones"] = [1, 1]
      d["label"] = ["l1", "l2"]
      tmp = d.groupby(["group"]).mean()
      res_values = np.array([[0, 1], [0, 1]], dtype=np.int64)
      tm.assert_index_equal(tmp.columns, Index(["zeros", "ones"]))
      tm.assert_numpy_array_equal(tmp.values, res_values)
  
  
  def test_int32_overflow():
      B = np.concatenate((np.arange(10000), np.arange(10000), np.arange(5000)))
      A = np.arange(25000)
      df = DataFrame({"A": A, "B": B, "C": A, "D": B, "E": np.random.randn(25000)})
  
      left = df.groupby(["A", "B", "C", "D"]).sum()
      right = df.groupby(["D", "C", "B", "A"]).sum()
      assert len(left) == len(right)
  
  
  def test_groupby_sort_multi():
      df = DataFrame(
          {
              "a": ["foo", "bar", "baz"],
              "b": [3, 2, 1],
              "c": [0, 1, 2],
              "d": np.random.randn(3),
          }
      )
  
      tups = [tuple(row) for row in df[["a", "b", "c"]].values]
      tups = com.asarray_tuplesafe(tups)
      result = df.groupby(["a", "b", "c"], sort=True).sum()
      tm.assert_numpy_array_equal(result.index.values, tups[[1, 2, 0]])
  
      tups = [tuple(row) for row in df[["c", "a", "b"]].values]
      tups = com.asarray_tuplesafe(tups)
      result = df.groupby(["c", "a", "b"], sort=True).sum()
      tm.assert_numpy_array_equal(result.index.values, tups)
  
      tups = [tuple(x) for x in df[["b", "c", "a"]].values]
      tups = com.asarray_tuplesafe(tups)
      result = df.groupby(["b", "c", "a"], sort=True).sum()
      tm.assert_numpy_array_equal(result.index.values, tups[[2, 1, 0]])
  
      df = DataFrame(
          {"a": [0, 1, 2, 0, 1, 2], "b": [0, 0, 0, 1, 1, 1], "d": np.random.randn(6)}
      )
      grouped = df.groupby(["a", "b"])["d"]
      result = grouped.sum()
  
      def _check_groupby(df, result, keys, field, f=lambda x: x.sum()):
          tups = [tuple(row) for row in df[keys].values]
          tups = com.asarray_tuplesafe(tups)
          expected = f(df.groupby(tups)[field])
          for k, v in expected.items():
              assert result[k] == v
  
      _check_groupby(df, result, ["a", "b"], "d")
  
  
  def test_dont_clobber_name_column():
      df = DataFrame(
          {"key": ["a", "a", "a", "b", "b", "b"], "name": ["foo", "bar", "baz"] * 2}
      )
  
      result = df.groupby("key").apply(lambda x: x)
      tm.assert_frame_equal(result, df)
  
  
  def test_skip_group_keys():
  
      tsf = tm.makeTimeDataFrame()
  
      grouped = tsf.groupby(lambda x: x.month, group_keys=False)
      result = grouped.apply(lambda x: x.sort_values(by="A")[:3])
  
      pieces = [group.sort_values(by="A")[:3] for key, group in grouped]
  
      expected = pd.concat(pieces)
      tm.assert_frame_equal(result, expected)
  
      grouped = tsf["A"].groupby(lambda x: x.month, group_keys=False)
      result = grouped.apply(lambda x: x.sort_values()[:3])
  
      pieces = [group.sort_values()[:3] for key, group in grouped]
  
      expected = pd.concat(pieces)
      tm.assert_series_equal(result, expected)
  
  
  def test_no_nonsense_name(float_frame):
      # GH #995
      s = float_frame["C"].copy()
      s.name = None
  
      result = s.groupby(float_frame["A"]).agg(np.sum)
      assert result.name is None
  
  
  def test_multifunc_sum_bug():
      # GH #1065
      x = DataFrame(np.arange(9).reshape(3, 3))
      x["test"] = 0
      x["fl"] = [1.3, 1.5, 1.6]
  
      grouped = x.groupby("test")
      result = grouped.agg({"fl": "sum", 2: "size"})
      assert result["fl"].dtype == np.float64
  
  
  def test_handle_dict_return_value(df):
      def f(group):
          return {"max": group.max(), "min": group.min()}
  
      def g(group):
          return Series({"max": group.max(), "min": group.min()})
  
      result = df.groupby("A")["C"].apply(f)
      expected = df.groupby("A")["C"].apply(g)
  
      assert isinstance(result, Series)
      tm.assert_series_equal(result, expected)
  
  
  @pytest.mark.parametrize("grouper", ["A", ["A", "B"]])
  def test_set_group_name(df, grouper):
      def f(group):
          assert group.name is not None
          return group
  
      def freduce(group):
          assert group.name is not None
          return group.sum()
  
      def foo(x):
          return freduce(x)
  
      grouped = df.groupby(grouper)
  
      # make sure all these work
      grouped.apply(f)
      grouped.aggregate(freduce)
      grouped.aggregate({"C": freduce, "D": freduce})
      grouped.transform(f)
  
      grouped["C"].apply(f)
      grouped["C"].aggregate(freduce)
      grouped["C"].aggregate([freduce, foo])
      grouped["C"].transform(f)
  
  
  def test_group_name_available_in_inference_pass():
      # gh-15062
      df = DataFrame({"a": [0, 0, 1, 1, 2, 2], "b": np.arange(6)})
  
      names = []
  
      def f(group):
          names.append(group.name)
          return group.copy()
  
      df.groupby("a", sort=False, group_keys=False).apply(f)
  
      expected_names = [0, 1, 2]
      assert names == expected_names
  
  
  def test_no_dummy_key_names(df):
      # see gh-1291
      result = df.groupby(df["A"].values).sum()
      assert result.index.name is None
  
      result = df.groupby([df["A"].values, df["B"].values]).sum()
      assert result.index.names == (None, None)
  
  
  def test_groupby_sort_multiindex_series():
      # series multiindex groupby sort argument was not being passed through
      # _compress_group_index
      # GH 9444
      index = MultiIndex(
          levels=[[1, 2], [1, 2]],
          codes=[[0, 0, 0, 0, 1, 1], [1, 1, 0, 0, 0, 0]],
          names=["a", "b"],
      )
      mseries = Series([0, 1, 2, 3, 4, 5], index=index)
      index = MultiIndex(
          levels=[[1, 2], [1, 2]], codes=[[0, 0, 1], [1, 0, 0]], names=["a", "b"]
      )
      mseries_result = Series([0, 2, 4], index=index)
  
      result = mseries.groupby(level=["a", "b"], sort=False).first()
      tm.assert_series_equal(result, mseries_result)
      result = mseries.groupby(level=["a", "b"], sort=True).first()
      tm.assert_series_equal(result, mseries_result.sort_index())
  
  
  def test_groupby_reindex_inside_function():
  
      periods = 1000
      ind = date_range(start="2012/1/1", freq="5min", periods=periods)
      df = DataFrame({"high": np.arange(periods), "low": np.arange(periods)}, index=ind)
  
      def agg_before(func, fix=False):
          """
          Run an aggregate func on the subset of data.
          """
  
          def _func(data):
              d = data.loc[data.index.map(lambda x: x.hour < 11)].dropna()
              if fix:
                  data[data.index[0]]
              if len(d) == 0:
                  return None
              return func(d)
  
          return _func
  
      grouped = df.groupby(lambda x: datetime(x.year, x.month, x.day))
      closure_bad = grouped.agg({"high": agg_before(np.max)})
      closure_good = grouped.agg({"high": agg_before(np.max, True)})
  
      tm.assert_frame_equal(closure_bad, closure_good)
  
  
  def test_groupby_multiindex_missing_pair():
      # GH9049
      df = DataFrame(
          {
              "group1": ["a", "a", "a", "b"],
              "group2": ["c", "c", "d", "c"],
              "value": [1, 1, 1, 5],
          }
      )
      df = df.set_index(["group1", "group2"])
      df_grouped = df.groupby(level=["group1", "group2"], sort=True)
  
      res = df_grouped.agg("sum")
      idx = MultiIndex.from_tuples(
          [("a", "c"), ("a", "d"), ("b", "c")], names=["group1", "group2"]
      )
      exp = DataFrame([[2], [1], [5]], index=idx, columns=["value"])
  
      tm.assert_frame_equal(res, exp)
  
  
  def test_groupby_multiindex_not_lexsorted():
      # GH 11640
  
      # define the lexsorted version
      lexsorted_mi = MultiIndex.from_tuples(
          [("a", ""), ("b1", "c1"), ("b2", "c2")], names=["b", "c"]
      )
      lexsorted_df = DataFrame([[1, 3, 4]], columns=lexsorted_mi)
      assert lexsorted_df.columns._is_lexsorted()
  
      # define the non-lexsorted version
      not_lexsorted_df = DataFrame(
          columns=["a", "b", "c", "d"], data=[[1, "b1", "c1", 3], [1, "b2", "c2", 4]]
      )
      not_lexsorted_df = not_lexsorted_df.pivot_table(
          index="a", columns=["b", "c"], values="d"
      )
      not_lexsorted_df = not_lexsorted_df.reset_index()
      assert not not_lexsorted_df.columns._is_lexsorted()
  
      # compare the results
      tm.assert_frame_equal(lexsorted_df, not_lexsorted_df)
  
      expected = lexsorted_df.groupby("a").mean()
      with tm.assert_produces_warning(PerformanceWarning):
          result = not_lexsorted_df.groupby("a").mean()
      tm.assert_frame_equal(expected, result)
  
      # a transforming function should work regardless of sort
      # GH 14776
      df = DataFrame(
          {"x": ["a", "a", "b", "a"], "y": [1, 1, 2, 2], "z": [1, 2, 3, 4]}
      ).set_index(["x", "y"])
      assert not df.index._is_lexsorted()
  
      for level in [0, 1, [0, 1]]:
          for sort in [False, True]:
              result = df.groupby(level=level, sort=sort).apply(DataFrame.drop_duplicates)
              expected = df
              tm.assert_frame_equal(expected, result)
  
              result = (
                  df.sort_index()
                  .groupby(level=level, sort=sort)
                  .apply(DataFrame.drop_duplicates)
              )
              expected = df.sort_index()
              tm.assert_frame_equal(expected, result)
  
  
  def test_index_label_overlaps_location():
      # checking we don't have any label/location confusion in the
      # wake of GH5375
      df = DataFrame(list("ABCDE"), index=[2, 0, 2, 1, 1])
      g = df.groupby(list("ababb"))
      actual = g.filter(lambda x: len(x) > 2)
      expected = df.iloc[[1, 3, 4]]
      tm.assert_frame_equal(actual, expected)
  
      ser = df[0]
      g = ser.groupby(list("ababb"))
      actual = g.filter(lambda x: len(x) > 2)
      expected = ser.take([1, 3, 4])
      tm.assert_series_equal(actual, expected)
  
      # ... and again, with a generic Index of floats
      df.index = df.index.astype(float)
      g = df.groupby(list("ababb"))
      actual = g.filter(lambda x: len(x) > 2)
      expected = df.iloc[[1, 3, 4]]
      tm.assert_frame_equal(actual, expected)
  
      ser = df[0]
      g = ser.groupby(list("ababb"))
      actual = g.filter(lambda x: len(x) > 2)
      expected = ser.take([1, 3, 4])
      tm.assert_series_equal(actual, expected)
  
  
  def test_transform_doesnt_clobber_ints():
      # GH 7972
      n = 6
      x = np.arange(n)
      df = DataFrame({"a": x // 2, "b": 2.0 * x, "c": 3.0 * x})
      df2 = DataFrame({"a": x // 2 * 1.0, "b": 2.0 * x, "c": 3.0 * x})
  
      gb = df.groupby("a")
      result = gb.transform("mean")
  
      gb2 = df2.groupby("a")
      expected = gb2.transform("mean")
      tm.assert_frame_equal(result, expected)
  
  
  @pytest.mark.parametrize(
      "sort_column",
      ["ints", "floats", "strings", ["ints", "floats"], ["ints", "strings"]],
  )
  @pytest.mark.parametrize(
      "group_column", ["int_groups", "string_groups", ["int_groups", "string_groups"]]
  )
  def test_groupby_preserves_sort(sort_column, group_column):
      # Test to ensure that groupby always preserves sort order of original
      # object. Issue #8588 and #9651
  
      df = DataFrame(
          {
              "int_groups": [3, 1, 0, 1, 0, 3, 3, 3],
              "string_groups": ["z", "a", "z", "a", "a", "g", "g", "g"],
              "ints": [8, 7, 4, 5, 2, 9, 1, 1],
              "floats": [2.3, 5.3, 6.2, -2.4, 2.2, 1.1, 1.1, 5],
              "strings": ["z", "d", "a", "e", "word", "word2", "42", "47"],
          }
      )
  
      # Try sorting on different types and with different group types
  
      df = df.sort_values(by=sort_column)
      g = df.groupby(group_column)
  
      def test_sort(x):
          tm.assert_frame_equal(x, x.sort_values(by=sort_column))
  
      g.apply(test_sort)
  
  
  def test_pivot_table_values_key_error():
      # This test is designed to replicate the error in issue #14938
      df = DataFrame(
          {
              "eventDate": date_range(datetime.today(), periods=20, freq="M").tolist(),
              "thename": range(0, 20),
          }
      )
  
      df["year"] = df.set_index("eventDate").index.year
      df["month"] = df.set_index("eventDate").index.month
  
      with pytest.raises(KeyError, match="'badname'"):
          df.reset_index().pivot_table(
              index="year", columns="month", values="badname", aggfunc="count"
          )
  
  
  @pytest.mark.parametrize("columns", ["C", ["C"]])
  @pytest.mark.parametrize("keys", [["A"], ["A", "B"]])
  @pytest.mark.parametrize(
      "values",
      [
          [True],
          [0],
          [0.0],
          ["a"],
          Categorical([0]),
          [to_datetime(0)],
          date_range(0, 1, 1, tz="US/Eastern"),
          pd.array([0], dtype="Int64"),
          pd.array([0], dtype="Float64"),
          pd.array([False], dtype="boolean"),
      ],
  )
  @pytest.mark.parametrize("method", ["attr", "agg", "apply"])
  @pytest.mark.parametrize(
      "op", ["idxmax", "idxmin", "mad", "min", "max", "sum", "prod", "skew"]
  )
  def test_empty_groupby(columns, keys, values, method, op, request):
      # GH8093 & GH26411
  
      if isinstance(values, Categorical) and len(keys) == 1 and method == "apply":
          mark = pytest.mark.xfail(raises=TypeError, match="'str' object is not callable")
          request.node.add_marker(mark)
      elif (
          isinstance(values, Categorical)
          and len(keys) == 1
          and op in ["idxmax", "idxmin"]
      ):
          mark = pytest.mark.xfail(
              raises=ValueError, match="attempt to get arg(min|max) of an empty sequence"
          )
          request.node.add_marker(mark)
      elif (
          isinstance(values, Categorical)
          and len(keys) == 1
          and not isinstance(columns, list)
      ):
          mark = pytest.mark.xfail(
              raises=TypeError, match="'Categorical' does not implement"
          )
          request.node.add_marker(mark)
      elif (
          isinstance(values, Categorical)
          and len(keys) == 1
          and op in ["mad", "min", "max", "sum", "prod", "skew"]
      ):
          mark = pytest.mark.xfail(
              raises=AssertionError, match="(DataFrame|Series) are different"
          )
          request.node.add_marker(mark)
      elif (
          isinstance(values, Categorical)
          and len(keys) == 2
          and op in ["min", "max", "sum"]
          and method != "apply"
      ):
          mark = pytest.mark.xfail(
              raises=AssertionError, match="(DataFrame|Series) are different"
          )
          request.node.add_marker(mark)
      elif (
          isinstance(values, pd.core.arrays.BooleanArray)
          and op in ["sum", "prod"]
          and method != "apply"
      ):
          mark = pytest.mark.xfail(
              raises=AssertionError, match="(DataFrame|Series) are different"
          )
          request.node.add_marker(mark)
  
      override_dtype = None
      if isinstance(values[0], bool) and op in ("prod", "sum") and method != "apply":
          # sum/product of bools is an integer
          override_dtype = "int64"
  
      df = DataFrame({"A": values, "B": values, "C": values}, columns=list("ABC"))
  
      if hasattr(values, "dtype"):
          # check that we did the construction right
          assert (df.dtypes == values.dtype).all()
  
      df = df.iloc[:0]
  
      gb = df.groupby(keys)[columns]
      if method == "attr":
          result = getattr(gb, op)()
      else:
          result = getattr(gb, method)(op)
  
      expected = df.set_index(keys)[columns]
      if override_dtype is not None:
          expected = expected.astype(override_dtype)
      if len(keys) == 1:
          expected.index.name = keys[0]
      tm.assert_equal(result, expected)
  
  
  def test_tuple_as_grouping():
      # https://github.com/pandas-dev/pandas/issues/18314
      df = DataFrame(
          {
              ("a", "b"): [1, 1, 1, 1],
              "a": [2, 2, 2, 2],
              "b": [2, 2, 2, 2],
              "c": [1, 1, 1, 1],
          }
      )
  
      with pytest.raises(KeyError, match=r"('a', 'b')"):
          df[["a", "b", "c"]].groupby(("a", "b"))
  
      result = df.groupby(("a", "b"))["c"].sum()
      expected = Series([4], name="c", index=Index([1], name=("a", "b")))
      tm.assert_series_equal(result, expected)
  
  
  def test_tuple_correct_keyerror():
      # https://github.com/pandas-dev/pandas/issues/18798
      df = DataFrame(1, index=range(3), columns=MultiIndex.from_product([[1, 2], [3, 4]]))
      with pytest.raises(KeyError, match=r"^\(7, 8\)$"):
          df.groupby((7, 8)).mean()
  
  
  def test_groupby_agg_ohlc_non_first():
      # GH 21716
      df = DataFrame(
          [[1], [1]],
          columns=["foo"],
          index=date_range("2018-01-01", periods=2, freq="D"),
      )
  
      expected = DataFrame(
          [[1, 1, 1, 1, 1], [1, 1, 1, 1, 1]],
          columns=MultiIndex.from_tuples(
              (
                  ("foo", "sum", "foo"),
                  ("foo", "ohlc", "open"),
                  ("foo", "ohlc", "high"),
                  ("foo", "ohlc", "low"),
                  ("foo", "ohlc", "close"),
              )
          ),
          index=date_range("2018-01-01", periods=2, freq="D"),
      )
  
      result = df.groupby(Grouper(freq="D")).agg(["sum", "ohlc"])
  
      tm.assert_frame_equal(result, expected)
  
  
  def test_groupby_multiindex_nat():
      # GH 9236
      values = [
          (pd.NaT, "a"),
          (datetime(2012, 1, 2), "a"),
          (datetime(2012, 1, 2), "b"),
          (datetime(2012, 1, 3), "a"),
      ]
      mi = MultiIndex.from_tuples(values, names=["date", None])
      ser = Series([3, 2, 2.5, 4], index=mi)
  
      result = ser.groupby(level=1).mean()
      expected = Series([3.0, 2.5], index=["a", "b"])
      tm.assert_series_equal(result, expected)
  
  
  def test_groupby_empty_list_raises():
      # GH 5289
      values = zip(range(10), range(10))
      df = DataFrame(values, columns=["apple", "b"])
      msg = "Grouper and axis must be same length"
      with pytest.raises(ValueError, match=msg):
          df.groupby([[]])
  
  
  def test_groupby_multiindex_series_keys_len_equal_group_axis():
      # GH 25704
      index_array = [["x", "x"], ["a", "b"], ["k", "k"]]
      index_names = ["first", "second", "third"]
      ri = MultiIndex.from_arrays(index_array, names=index_names)
      s = Series(data=[1, 2], index=ri)
      result = s.groupby(["first", "third"]).sum()
  
      index_array = [["x"], ["k"]]
      index_names = ["first", "third"]
      ei = MultiIndex.from_arrays(index_array, names=index_names)
      expected = Series([3], index=ei)
  
      tm.assert_series_equal(result, expected)
  
  
  def test_groupby_groups_in_BaseGrouper():
      # GH 26326
      # Test if DataFrame grouped with a pandas.Grouper has correct groups
      mi = MultiIndex.from_product([["A", "B"], ["C", "D"]], names=["alpha", "beta"])
      df = DataFrame({"foo": [1, 2, 1, 2], "bar": [1, 2, 3, 4]}, index=mi)
      result = df.groupby([Grouper(level="alpha"), "beta"])
      expected = df.groupby(["alpha", "beta"])
      assert result.groups == expected.groups
  
      result = df.groupby(["beta", Grouper(level="alpha")])
      expected = df.groupby(["beta", "alpha"])
      assert result.groups == expected.groups
  
  
  @pytest.mark.parametrize("group_name", ["x", ["x"]])
  def test_groupby_axis_1(group_name):
      # GH 27614
      df = DataFrame(
          np.arange(12).reshape(3, 4), index=[0, 1, 0], columns=[10, 20, 10, 20]
      )
      df.index.name = "y"
      df.columns.name = "x"
  
      results = df.groupby(group_name, axis=1).sum()
      expected = df.T.groupby(group_name).sum().T
      tm.assert_frame_equal(results, expected)
  
      # test on MI column
      iterables = [["bar", "baz", "foo"], ["one", "two"]]
      mi = MultiIndex.from_product(iterables=iterables, names=["x", "x1"])
      df = DataFrame(np.arange(18).reshape(3, 6), index=[0, 1, 0], columns=mi)
      results = df.groupby(group_name, axis=1).sum()
      expected = df.T.groupby(group_name).sum().T
      tm.assert_frame_equal(results, expected)
  
  
  @pytest.mark.parametrize(
      "op, expected",
      [
          (
              "shift",
              {
                  "time": [
                      None,
                      None,
                      Timestamp("2019-01-01 12:00:00"),
                      Timestamp("2019-01-01 12:30:00"),
                      None,
                      None,
                  ]
              },
          ),
          (
              "bfill",
              {
                  "time": [
                      Timestamp("2019-01-01 12:00:00"),
                      Timestamp("2019-01-01 12:30:00"),
                      Timestamp("2019-01-01 14:00:00"),
                      Timestamp("2019-01-01 14:30:00"),
                      Timestamp("2019-01-01 14:00:00"),
                      Timestamp("2019-01-01 14:30:00"),
                  ]
              },
          ),
          (
              "ffill",
              {
                  "time": [
                      Timestamp("2019-01-01 12:00:00"),
                      Timestamp("2019-01-01 12:30:00"),
                      Timestamp("2019-01-01 12:00:00"),
                      Timestamp("2019-01-01 12:30:00"),
                      Timestamp("2019-01-01 14:00:00"),
                      Timestamp("2019-01-01 14:30:00"),
                  ]
              },
          ),
      ],
  )
  def test_shift_bfill_ffill_tz(tz_naive_fixture, op, expected):
      # GH19995, GH27992: Check that timezone does not drop in shift, bfill, and ffill
      tz = tz_naive_fixture
      data = {
          "id": ["A", "B", "A", "B", "A", "B"],
          "time": [
              Timestamp("2019-01-01 12:00:00"),
              Timestamp("2019-01-01 12:30:00"),
              None,
              None,
              Timestamp("2019-01-01 14:00:00"),
              Timestamp("2019-01-01 14:30:00"),
          ],
      }
      df = DataFrame(data).assign(time=lambda x: x.time.dt.tz_localize(tz))
  
      grouped = df.groupby("id")
      result = getattr(grouped, op)()
      expected = DataFrame(expected).assign(time=lambda x: x.time.dt.tz_localize(tz))
      tm.assert_frame_equal(result, expected)
  
  
  def test_groupby_only_none_group():
      # see GH21624
      # this was crashing with "ValueError: Length of passed values is 1, index implies 0"
      df = DataFrame({"g": [None], "x": 1})
      actual = df.groupby("g")["x"].transform("sum")
      expected = Series([np.nan], name="x")
  
      tm.assert_series_equal(actual, expected)
  
  
  def test_groupby_duplicate_index():
      # GH#29189 the groupby call here used to raise
      ser = Series([2, 5, 6, 8], index=[2.0, 4.0, 4.0, 5.0])
      gb = ser.groupby(level=0)
  
      result = gb.mean()
      expected = Series([2, 5.5, 8], index=[2.0, 4.0, 5.0])
      tm.assert_series_equal(result, expected)
  
  
  @pytest.mark.parametrize(
      "idx", [Index(["a", "a"]), MultiIndex.from_tuples((("a", "a"), ("a", "a")))]
  )
  @pytest.mark.filterwarnings("ignore:tshift is deprecated:FutureWarning")
  def test_dup_labels_output_shape(groupby_func, idx):
      if groupby_func in {"size", "ngroup", "cumcount"}:
          pytest.skip("Not applicable")
  
      df = DataFrame([[1, 1]], columns=idx)
      grp_by = df.groupby([0])
  
      args = []
      if groupby_func in {"fillna", "nth"}:
          args.append(0)
      elif groupby_func == "corrwith":
          args.append(df)
      elif groupby_func == "tshift":
          df.index = [Timestamp("today")]
          args.extend([1, "D"])
  
      result = getattr(grp_by, groupby_func)(*args)
  
      assert result.shape == (1, 2)
      tm.assert_index_equal(result.columns, idx)
  
  
  def test_groupby_crash_on_nunique(axis):
      # Fix following 30253
      df = DataFrame({("A", "B"): [1, 2], ("A", "C"): [1, 3], ("D", "B"): [0, 0]})
  
      axis_number = df._get_axis_number(axis)
      if not axis_number:
          df = df.T
  
      result = df.groupby(axis=axis_number, level=0).nunique()
  
      expected = DataFrame({"A": [1, 2], "D": [1, 1]})
      if not axis_number:
          expected = expected.T
  
      tm.assert_frame_equal(result, expected)
  
      # same thing, but empty columns
      gb = df[[]].groupby(axis=axis_number, level=0)
      res = gb.nunique()
      exp = expected[[]]
      tm.assert_frame_equal(res, exp)
  
  
  def test_groupby_list_level():
      # GH 9790
      expected = DataFrame(np.arange(0, 9).reshape(3, 3))
      result = expected.groupby(level=[0]).mean()
      tm.assert_frame_equal(result, expected)
  
  
  @pytest.mark.parametrize(
      "max_seq_items, expected",
      [
          (5, "{0: [0], 1: [1], 2: [2], 3: [3], 4: [4]}"),
          (4, "{0: [0], 1: [1], 2: [2], 3: [3], ...}"),
          (1, "{0: [0], ...}"),
      ],
  )
  def test_groups_repr_truncates(max_seq_items, expected):
      # GH 1135
      df = DataFrame(np.random.randn(5, 1))
      df["a"] = df.index
  
      with pd.option_context("display.max_seq_items", max_seq_items):
          result = df.groupby("a").groups.__repr__()
          assert result == expected
  
          result = df.groupby(np.array(df.a)).groups.__repr__()
          assert result == expected
  
  
  def test_group_on_two_row_multiindex_returns_one_tuple_key():
      # GH 18451
      df = DataFrame([{"a": 1, "b": 2, "c": 99}, {"a": 1, "b": 2, "c": 88}])
      df = df.set_index(["a", "b"])
  
      grp = df.groupby(["a", "b"])
      result = grp.indices
      expected = {(1, 2): np.array([0, 1], dtype=np.int64)}
  
      assert len(result) == 1
      key = (1, 2)
      assert (result[key] == expected[key]).all()
  
  
  @pytest.mark.parametrize(
      "klass, attr, value",
      [
          (DataFrame, "level", "a"),
          (DataFrame, "as_index", False),
          (DataFrame, "sort", False),
          (DataFrame, "group_keys", False),
          (DataFrame, "squeeze", True),
          (DataFrame, "observed", True),
          (DataFrame, "dropna", False),
          pytest.param(
              Series,
              "axis",
              1,
              marks=pytest.mark.xfail(
                  reason="GH 35443: Attribute currently not passed on to series"
              ),
          ),
          (Series, "level", "a"),
          (Series, "as_index", False),
          (Series, "sort", False),
          (Series, "group_keys", False),
          (Series, "squeeze", True),
          (Series, "observed", True),
          (Series, "dropna", False),
      ],
  )
  @pytest.mark.filterwarnings(
      "ignore:The `squeeze` parameter is deprecated:FutureWarning"
  )
  def test_subsetting_columns_keeps_attrs(klass, attr, value):
      # GH 9959 - When subsetting columns, don't drop attributes
      df = DataFrame({"a": [1], "b": [2], "c": [3]})
      if attr != "axis":
          df = df.set_index("a")
  
      expected = df.groupby("a", **{attr: value})
      result = expected[["b"]] if klass is DataFrame else expected["b"]
      assert getattr(result, attr) == getattr(expected, attr)
  
  
  def test_subsetting_columns_axis_1():
      # GH 37725
      g = DataFrame({"A": [1], "B": [2], "C": [3]}).groupby([0, 0, 1], axis=1)
      match = "Cannot subset columns when using axis=1"
      with pytest.raises(ValueError, match=match):
          g[["A", "B"]].sum()
  
  
  @pytest.mark.parametrize("func", ["sum", "any", "shift"])
  def test_groupby_column_index_name_lost(func):
      # GH: 29764 groupby loses index sometimes
      expected = Index(["a"], name="idx")
      df = DataFrame([[1]], columns=expected)
      df_grouped = df.groupby([1])
      result = getattr(df_grouped, func)().columns
      tm.assert_index_equal(result, expected)
  
  
  def test_groupby_duplicate_columns():
      # GH: 31735
      df = DataFrame(
          {"A": ["f", "e", "g", "h"], "B": ["a", "b", "c", "d"], "C": [1, 2, 3, 4]}
      ).astype(object)
      df.columns = ["A", "B", "B"]
      result = df.groupby([0, 0, 0, 0]).min()
      expected = DataFrame([["e", "a", 1]], columns=["A", "B", "B"])
      tm.assert_frame_equal(result, expected)
  
  
  def test_groupby_series_with_tuple_name():
      # GH 37755
      ser = Series([1, 2, 3, 4], index=[1, 1, 2, 2], name=("a", "a"))
      ser.index.name = ("b", "b")
      result = ser.groupby(level=0).last()
      expected = Series([2, 4], index=[1, 2], name=("a", "a"))
      expected.index.name = ("b", "b")
      tm.assert_series_equal(result, expected)
  
  
  @pytest.mark.xfail(not IS64, reason="GH#38778: fail on 32-bit system")
  @pytest.mark.parametrize(
      "func, values", [("sum", [97.0, 98.0]), ("mean", [24.25, 24.5])]
  )
  def test_groupby_numerical_stability_sum_mean(func, values):
      # GH#38778
      data = [1e16, 1e16, 97, 98, -5e15, -5e15, -5e15, -5e15]
      df = DataFrame({"group": [1, 2] * 4, "a": data, "b": data})
      result = getattr(df.groupby("group"), func)()
      expected = DataFrame({"a": values, "b": values}, index=Index([1, 2], name="group"))
      tm.assert_frame_equal(result, expected)
  
  
  @pytest.mark.xfail(not IS64, reason="GH#38778: fail on 32-bit system")
  def test_groupby_numerical_stability_cumsum():
      # GH#38934
      data = [1e16, 1e16, 97, 98, -5e15, -5e15, -5e15, -5e15]
      df = DataFrame({"group": [1, 2] * 4, "a": data, "b": data})
      result = df.groupby("group").cumsum()
      exp_data = (
          [1e16] * 2 + [1e16 + 96, 1e16 + 98] + [5e15 + 97, 5e15 + 98] + [97.0, 98.0]
      )
      expected = DataFrame({"a": exp_data, "b": exp_data})
      tm.assert_frame_equal(result, expected, check_exact=True)
  
  
  def test_groupby_mean_duplicate_index(rand_series_with_duplicate_datetimeindex):
      dups = rand_series_with_duplicate_datetimeindex
      result = dups.groupby(level=0).mean()
      expected = dups.groupby(dups.index).mean()
      tm.assert_series_equal(result, expected)
  
apis: pandas._testing.assert_numpy_array_equal numpy.ones numpy.sum pandas.Series pandas.array pandas._testing.assert_frame_equal pandas.Categorical pandas._testing.assert_series_equal pandas.Grouper pandas._testing.assert_produces_warning pandas._testing.assert_equal pandas._testing.assert_almost_equal pandas.to_datetime pandas.Timestamp pandas.date_range pandas.core.common.asarray_tuplesafe pandas.MultiIndex.from_product numpy.arange pandas.MultiIndex.from_tuples pandas.concat numpy.std pandas.Index numpy.array numpy.percentile numpy.random.shuffle pandas._testing.makeTimeDataFrame numpy.empty pandas.MultiIndex.from_arrays pandas.DataFrame numpy.random.randn numpy.random.random pandas._testing.assert_index_equal pandas._testing.rands_array pandas.MultiIndex numpy.random.randint pandas.option_context