from datetime import date, datetime, timedelta import random import re import numpy as np import pytest from pandas.core.dtypes.common import is_categorical_dtype, is_object_dtype from pandas.core.dtypes.dtypes import CategoricalDtype import pandas as pd from pandas import ( Categorical, CategoricalIndex, DataFrame, DatetimeIndex, Float64Index, Int64Index, IntervalIndex, MultiIndex, PeriodIndex, RangeIndex, Series, TimedeltaIndex, UInt64Index, ) import pandas._testing as tm from pandas.api.types import CategoricalDtype as CDT from pandas.core.reshape.concat import concat from pandas.core.reshape.merge import MergeError, merge N = 50 NGROUPS = 8 def get_test_data(ngroups=NGROUPS, n=N): unique_groups = list(range(ngroups)) arr = np.asarray(np.tile(unique_groups, n // ngroups)) if len(arr) < n: arr = np.asarray(list(arr) + unique_groups[: n - len(arr)]) random.shuffle(arr) return arr def get_series(): return [ Series([1], dtype="int64"), Series([1], dtype="Int64"), Series([1.23]), Series(["foo"]), Series([True]), Series([pd.Timestamp("2018-01-01")]), Series([pd.Timestamp("2018-01-01", tz="US/Eastern")]), ] def get_series_na(): return [ Series([np.nan], dtype="Int64"), Series([np.nan], dtype="float"), Series([np.nan], dtype="object"), Series([pd.NaT]), ] @pytest.fixture(params=get_series(), ids=lambda x: x.dtype.name) def series_of_dtype(request): """ A parametrized fixture returning a variety of Series of different dtypes """ return request.param @pytest.fixture(params=get_series(), ids=lambda x: x.dtype.name) def series_of_dtype2(request): """ A duplicate of the series_of_dtype fixture, so that it can be used twice by a single function """ return request.param @pytest.fixture(params=get_series_na(), ids=lambda x: x.dtype.name) def series_of_dtype_all_na(request): """ A parametrized fixture returning a variety of Series with all NA values """ return request.param class TestMerge: def setup_method(self, method): # aggregate multiple columns self.df = DataFrame( { "key1": get_test_data(), "key2": get_test_data(), "data1": np.random.randn(N), "data2": np.random.randn(N), } ) # exclude a couple keys for fun self.df = self.df[self.df["key2"] > 1] self.df2 = DataFrame( { "key1": get_test_data(n=N // 5), "key2": get_test_data(ngroups=NGROUPS // 2, n=N // 5), "value": np.random.randn(N // 5), } ) self.left = DataFrame( {"key": ["a", "b", "c", "d", "e", "e", "a"], "v1": np.random.randn(7)} ) self.right = DataFrame({"v2": np.random.randn(4)}, index=["d", "b", "c", "a"]) def test_merge_inner_join_empty(self): # GH 15328 df_empty = DataFrame() df_a = DataFrame({"a": [1, 2]}, index=[0, 1], dtype="int64") result = pd.merge(df_empty, df_a, left_index=True, right_index=True) expected = DataFrame({"a": []}, index=[], dtype="int64") tm.assert_frame_equal(result, expected) def test_merge_common(self): joined = merge(self.df, self.df2) exp = merge(self.df, self.df2, on=["key1", "key2"]) tm.assert_frame_equal(joined, exp) def test_merge_non_string_columns(self): # https://github.com/pandas-dev/pandas/issues/17962 # Checks that method runs for non string column names left = DataFrame( {0: [1, 0, 1, 0], 1: [0, 1, 0, 0], 2: [0, 0, 2, 0], 3: [1, 0, 0, 3]} ) right = left.astype(float) expected = left result = pd.merge(left, right) tm.assert_frame_equal(expected, result) def test_merge_index_as_on_arg(self): # GH14355 left = self.df.set_index("key1") right = self.df2.set_index("key1") result = merge(left, right, on="key1") expected = merge(self.df, self.df2, on="key1").set_index("key1") tm.assert_frame_equal(result, expected) def test_merge_index_singlekey_right_vs_left(self): left = DataFrame( {"key": ["a", "b", "c", "d", "e", "e", "a"], "v1": np.random.randn(7)} ) right = DataFrame({"v2": np.random.randn(4)}, index=["d", "b", "c", "a"]) merged1 = merge( left, right, left_on="key", right_index=True, how="left", sort=False ) merged2 = merge( right, left, right_on="key", left_index=True, how="right", sort=False ) tm.assert_frame_equal(merged1, merged2.loc[:, merged1.columns]) merged1 = merge( left, right, left_on="key", right_index=True, how="left", sort=True ) merged2 = merge( right, left, right_on="key", left_index=True, how="right", sort=True ) tm.assert_frame_equal(merged1, merged2.loc[:, merged1.columns]) def test_merge_index_singlekey_inner(self): left = DataFrame( {"key": ["a", "b", "c", "d", "e", "e", "a"], "v1": np.random.randn(7)} ) right = DataFrame({"v2": np.random.randn(4)}, index=["d", "b", "c", "a"]) # inner join result = merge(left, right, left_on="key", right_index=True, how="inner") expected = left.join(right, on="key").loc[result.index] tm.assert_frame_equal(result, expected) result = merge(right, left, right_on="key", left_index=True, how="inner") expected = left.join(right, on="key").loc[result.index] tm.assert_frame_equal(result, expected.loc[:, result.columns]) def test_merge_misspecified(self): msg = "Must pass right_on or right_index=True" with pytest.raises(pd.errors.MergeError, match=msg): merge(self.left, self.right, left_index=True) msg = "Must pass left_on or left_index=True" with pytest.raises(pd.errors.MergeError, match=msg): merge(self.left, self.right, right_index=True) msg = ( 'Can only pass argument "on" OR "left_on" and "right_on", not ' "a combination of both" ) with pytest.raises(pd.errors.MergeError, match=msg): merge(self.left, self.left, left_on="key", on="key") msg = r"len\(right_on\) must equal len\(left_on\)" with pytest.raises(ValueError, match=msg): merge(self.df, self.df2, left_on=["key1"], right_on=["key1", "key2"]) def test_index_and_on_parameters_confusion(self): msg = "right_index parameter must be of type bool, not " with pytest.raises(ValueError, match=msg): merge( self.df, self.df2, how="left", left_index=False, right_index=["key1", "key2"], ) msg = "left_index parameter must be of type bool, not " with pytest.raises(ValueError, match=msg): merge( self.df, self.df2, how="left", left_index=["key1", "key2"], right_index=False, ) with pytest.raises(ValueError, match=msg): merge( self.df, self.df2, how="left", left_index=["key1", "key2"], right_index=["key1", "key2"], ) def test_merge_overlap(self): merged = merge(self.left, self.left, on="key") exp_len = (self.left["key"].value_counts() ** 2).sum() assert len(merged) == exp_len assert "v1_x" in merged assert "v1_y" in merged def test_merge_different_column_key_names(self): left = DataFrame({"lkey": ["foo", "bar", "baz", "foo"], "value": [1, 2, 3, 4]}) right = DataFrame({"rkey": ["foo", "bar", "qux", "foo"], "value": [5, 6, 7, 8]}) merged = left.merge( right, left_on="lkey", right_on="rkey", how="outer", sort=True ) exp = Series(["bar", "baz", "foo", "foo", "foo", "foo", np.nan], name="lkey") tm.assert_series_equal(merged["lkey"], exp) exp = Series(["bar", np.nan, "foo", "foo", "foo", "foo", "qux"], name="rkey") tm.assert_series_equal(merged["rkey"], exp) exp = Series([2, 3, 1, 1, 4, 4, np.nan], name="value_x") tm.assert_series_equal(merged["value_x"], exp) exp = Series([6, np.nan, 5, 8, 5, 8, 7], name="value_y") tm.assert_series_equal(merged["value_y"], exp) def test_merge_copy(self): left = DataFrame({"a": 0, "b": 1}, index=range(10)) right = DataFrame({"c": "foo", "d": "bar"}, index=range(10)) merged = merge(left, right, left_index=True, right_index=True, copy=True) merged["a"] = 6 assert (left["a"] == 0).all() merged["d"] = "peekaboo" assert (right["d"] == "bar").all() def test_merge_nocopy(self): left = DataFrame({"a": 0, "b": 1}, index=range(10)) right = DataFrame({"c": "foo", "d": "bar"}, index=range(10)) merged = merge(left, right, left_index=True, right_index=True, copy=False) merged["a"] = 6 assert (left["a"] == 6).all() merged["d"] = "peekaboo" assert (right["d"] == "peekaboo").all() def test_intelligently_handle_join_key(self): # #733, be a bit more 1337 about not returning unconsolidated DataFrame left = DataFrame( {"key": [1, 1, 2, 2, 3], "value": list(range(5))}, columns=["value", "key"] ) right = DataFrame({"key": [1, 1, 2, 3, 4, 5], "rvalue": list(range(6))}) joined = merge(left, right, on="key", how="outer") expected = DataFrame( { "key": [1, 1, 1, 1, 2, 2, 3, 4, 5], "value": np.array([0, 0, 1, 1, 2, 3, 4, np.nan, np.nan]), "rvalue": [0, 1, 0, 1, 2, 2, 3, 4, 5], }, columns=["value", "key", "rvalue"], ) tm.assert_frame_equal(joined, expected) def test_merge_join_key_dtype_cast(self): # #8596 df1 = DataFrame({"key": [1], "v1": [10]}) df2 = DataFrame({"key": [2], "v1": [20]}) df = merge(df1, df2, how="outer") assert df["key"].dtype == "int64" df1 = DataFrame({"key": [True], "v1": [1]}) df2 = DataFrame({"key": [False], "v1": [0]}) df = merge(df1, df2, how="outer") # GH13169 # this really should be bool assert df["key"].dtype == "object" df1 = DataFrame({"val": [1]}) df2 = DataFrame({"val": [2]}) lkey = np.array([1]) rkey = np.array([2]) df = merge(df1, df2, left_on=lkey, right_on=rkey, how="outer") assert df["key_0"].dtype == "int64" def test_handle_join_key_pass_array(self): left = DataFrame( {"key": [1, 1, 2, 2, 3], "value": np.arange(5)}, columns=["value", "key"] ) right = DataFrame({"rvalue": np.arange(6)}) key = np.array([1, 1, 2, 3, 4, 5]) merged = merge(left, right, left_on="key", right_on=key, how="outer") merged2 = merge(right, left, left_on=key, right_on="key", how="outer") tm.assert_series_equal(merged["key"], merged2["key"]) assert merged["key"].notna().all() assert merged2["key"].notna().all() left = DataFrame({"value": np.arange(5)}, columns=["value"]) right = DataFrame({"rvalue": np.arange(6)}) lkey = np.array([1, 1, 2, 2, 3]) rkey = np.array([1, 1, 2, 3, 4, 5]) merged = merge(left, right, left_on=lkey, right_on=rkey, how="outer") tm.assert_series_equal( merged["key_0"], Series([1, 1, 1, 1, 2, 2, 3, 4, 5], name="key_0") ) left = DataFrame({"value": np.arange(3)}) right = DataFrame({"rvalue": np.arange(6)}) key = np.array([0, 1, 1, 2, 2, 3], dtype=np.int64) merged = merge(left, right, left_index=True, right_on=key, how="outer") tm.assert_series_equal(merged["key_0"], Series(key, name="key_0")) def test_no_overlap_more_informative_error(self): dt = datetime.now() df1 = DataFrame({"x": ["a"]}, index=[dt]) df2 = DataFrame({"y": ["b", "c"]}, index=[dt, dt]) msg = ( "No common columns to perform merge on. " f"Merge options: left_on={None}, right_on={None}, " f"left_index={False}, right_index={False}" ) with pytest.raises(MergeError, match=msg): merge(df1, df2) def test_merge_non_unique_indexes(self): dt = datetime(2012, 5, 1) dt2 = datetime(2012, 5, 2) dt3 = datetime(2012, 5, 3) dt4 = datetime(2012, 5, 4) df1 = DataFrame({"x": ["a"]}, index=[dt]) df2 = DataFrame({"y": ["b", "c"]}, index=[dt, dt]) _check_merge(df1, df2) # Not monotonic df1 = DataFrame({"x": ["a", "b", "q"]}, index=[dt2, dt, dt4]) df2 = DataFrame( {"y": ["c", "d", "e", "f", "g", "h"]}, index=[dt3, dt3, dt2, dt2, dt, dt] ) _check_merge(df1, df2) df1 = DataFrame({"x": ["a", "b"]}, index=[dt, dt]) df2 = DataFrame({"y": ["c", "d"]}, index=[dt, dt]) _check_merge(df1, df2) def test_merge_non_unique_index_many_to_many(self): dt = datetime(2012, 5, 1) dt2 = datetime(2012, 5, 2) dt3 = datetime(2012, 5, 3) df1 = DataFrame({"x": ["a", "b", "c", "d"]}, index=[dt2, dt2, dt, dt]) df2 = DataFrame( {"y": ["e", "f", "g", " h", "i"]}, index=[dt2, dt2, dt3, dt, dt] ) _check_merge(df1, df2) def test_left_merge_empty_dataframe(self): left = DataFrame({"key": [1], "value": [2]}) right = DataFrame({"key": []}) result = merge(left, right, on="key", how="left") tm.assert_frame_equal(result, left) result = merge(right, left, on="key", how="right") tm.assert_frame_equal(result, left) @pytest.mark.parametrize( "kwarg", [ {"left_index": True, "right_index": True}, {"left_index": True, "right_on": "x"}, {"left_on": "a", "right_index": True}, {"left_on": "a", "right_on": "x"}, ], ) def test_merge_left_empty_right_empty(self, join_type, kwarg): # GH 10824 left = DataFrame(columns=["a", "b", "c"]) right = DataFrame(columns=["x", "y", "z"]) exp_in = DataFrame( columns=["a", "b", "c", "x", "y", "z"], index=pd.Index([], dtype=object), dtype=object, ) result = pd.merge(left, right, how=join_type, **kwarg) tm.assert_frame_equal(result, exp_in) def test_merge_left_empty_right_notempty(self): # GH 10824 left = DataFrame(columns=["a", "b", "c"]) right = DataFrame([[1, 2, 3], [4, 5, 6], [7, 8, 9]], columns=["x", "y", "z"]) exp_out = DataFrame( { "a": np.array([np.nan] * 3, dtype=object), "b": np.array([np.nan] * 3, dtype=object), "c": np.array([np.nan] * 3, dtype=object), "x": [1, 4, 7], "y": [2, 5, 8], "z": [3, 6, 9], }, columns=["a", "b", "c", "x", "y", "z"], ) exp_in = exp_out[0:0] # make empty DataFrame keeping dtype # result will have object dtype exp_in.index = exp_in.index.astype(object) def check1(exp, kwarg): result = pd.merge(left, right, how="inner", **kwarg) tm.assert_frame_equal(result, exp) result = pd.merge(left, right, how="left", **kwarg) tm.assert_frame_equal(result, exp) def check2(exp, kwarg): result = pd.merge(left, right, how="right", **kwarg) tm.assert_frame_equal(result, exp) result = pd.merge(left, right, how="outer", **kwarg) tm.assert_frame_equal(result, exp) for kwarg in [ {"left_index": True, "right_index": True}, {"left_index": True, "right_on": "x"}, ]: check1(exp_in, kwarg) check2(exp_out, kwarg) kwarg = {"left_on": "a", "right_index": True} check1(exp_in, kwarg) exp_out["a"] = [0, 1, 2] check2(exp_out, kwarg) kwarg = {"left_on": "a", "right_on": "x"} check1(exp_in, kwarg) exp_out["a"] = np.array([np.nan] * 3, dtype=object) check2(exp_out, kwarg) def test_merge_left_notempty_right_empty(self): # GH 10824 left = DataFrame([[1, 2, 3], [4, 5, 6], [7, 8, 9]], columns=["a", "b", "c"]) right = DataFrame(columns=["x", "y", "z"]) exp_out = DataFrame( { "a": [1, 4, 7], "b": [2, 5, 8], "c": [3, 6, 9], "x": np.array([np.nan] * 3, dtype=object), "y": np.array([np.nan] * 3, dtype=object), "z": np.array([np.nan] * 3, dtype=object), }, columns=["a", "b", "c", "x", "y", "z"], ) exp_in = exp_out[0:0] # make empty DataFrame keeping dtype # result will have object dtype exp_in.index = exp_in.index.astype(object) def check1(exp, kwarg): result = pd.merge(left, right, how="inner", **kwarg) tm.assert_frame_equal(result, exp) result = pd.merge(left, right, how="right", **kwarg) tm.assert_frame_equal(result, exp) def check2(exp, kwarg): result = pd.merge(left, right, how="left", **kwarg) tm.assert_frame_equal(result, exp) result = pd.merge(left, right, how="outer", **kwarg) tm.assert_frame_equal(result, exp) for kwarg in [ {"left_index": True, "right_index": True}, {"left_index": True, "right_on": "x"}, {"left_on": "a", "right_index": True}, {"left_on": "a", "right_on": "x"}, ]: check1(exp_in, kwarg) check2(exp_out, kwarg) def test_merge_empty_frame(self, series_of_dtype, series_of_dtype2): # GH 25183 df = DataFrame( {"key": series_of_dtype, "value": series_of_dtype2}, columns=["key", "value"], ) df_empty = df[:0] expected = DataFrame( { "value_x": Series(dtype=df.dtypes["value"]), "key": Series(dtype=df.dtypes["key"]), "value_y": Series(dtype=df.dtypes["value"]), }, columns=["value_x", "key", "value_y"], ) actual = df_empty.merge(df, on="key") tm.assert_frame_equal(actual, expected) def test_merge_all_na_column(self, series_of_dtype, series_of_dtype_all_na): # GH 25183 df_left = DataFrame( {"key": series_of_dtype, "value": series_of_dtype_all_na}, columns=["key", "value"], ) df_right = DataFrame( {"key": series_of_dtype, "value": series_of_dtype_all_na}, columns=["key", "value"], ) expected = DataFrame( { "key": series_of_dtype, "value_x": series_of_dtype_all_na, "value_y": series_of_dtype_all_na, }, columns=["key", "value_x", "value_y"], ) actual = df_left.merge(df_right, on="key") tm.assert_frame_equal(actual, expected) def test_merge_nosort(self): # GH#2098, TODO: anything to do? d = { "var1": np.random.randint(0, 10, size=10), "var2": np.random.randint(0, 10, size=10), "var3": [ datetime(2012, 1, 12), datetime(2011, 2, 4), datetime(2010, 2, 3), datetime(2012, 1, 12), datetime(2011, 2, 4), datetime(2012, 4, 3), datetime(2012, 3, 4), datetime(2008, 5, 1), datetime(2010, 2, 3), datetime(2012, 2, 3), ], } df = DataFrame.from_dict(d) var3 = df.var3.unique() var3.sort() new = DataFrame.from_dict({"var3": var3, "var8": np.random.random(7)}) result = df.merge(new, on="var3", sort=False) exp = merge(df, new, on="var3", sort=False) tm.assert_frame_equal(result, exp) assert (df.var3.unique() == result.var3.unique()).all() @pytest.mark.parametrize( ("sort", "values"), [(False, [1, 1, 0, 1, 1]), (True, [0, 1, 1, 1, 1])] ) @pytest.mark.parametrize("how", ["left", "right"]) def test_merge_same_order_left_right(self, sort, values, how): # GH#35382 df = DataFrame({"a": [1, 0, 1]}) result = df.merge(df, on="a", how=how, sort=sort) expected = DataFrame(values, columns=["a"]) tm.assert_frame_equal(result, expected) def test_merge_nan_right(self): df1 = DataFrame({"i1": [0, 1], "i2": [0, 1]}) df2 = DataFrame({"i1": [0], "i3": [0]}) result = df1.join(df2, on="i1", rsuffix="_") expected = ( DataFrame( { "i1": {0: 0.0, 1: 1}, "i2": {0: 0, 1: 1}, "i1_": {0: 0, 1: np.nan}, "i3": {0: 0.0, 1: np.nan}, None: {0: 0, 1: 0}, } ) .set_index(None) .reset_index()[["i1", "i2", "i1_", "i3"]] ) tm.assert_frame_equal(result, expected, check_dtype=False) df1 = DataFrame({"i1": [0, 1], "i2": [0.5, 1.5]}) df2 = DataFrame({"i1": [0], "i3": [0.7]}) result = df1.join(df2, rsuffix="_", on="i1") expected = DataFrame( { "i1": {0: 0, 1: 1}, "i1_": {0: 0.0, 1: np.nan}, "i2": {0: 0.5, 1: 1.5}, "i3": {0: 0.69999999999999996, 1: np.nan}, } )[["i1", "i2", "i1_", "i3"]] tm.assert_frame_equal(result, expected) def test_merge_type(self): class NotADataFrame(DataFrame): @property def _constructor(self): return NotADataFrame nad = NotADataFrame(self.df) result = nad.merge(self.df2, on="key1") assert isinstance(result, NotADataFrame) def test_join_append_timedeltas(self): # timedelta64 issues with join/merge # GH 5695 d = {"d": datetime(2013, 11, 5, 5, 56), "t": timedelta(0, 22500)} df = DataFrame(columns=list("dt")) df = df.append(d, ignore_index=True) result = df.append(d, ignore_index=True) expected = DataFrame( { "d": [datetime(2013, 11, 5, 5, 56), datetime(2013, 11, 5, 5, 56)], "t": [timedelta(0, 22500), timedelta(0, 22500)], } ) tm.assert_frame_equal(result, expected) td = np.timedelta64(300000000) lhs = DataFrame(Series([td, td], index=["A", "B"])) rhs = DataFrame(Series([td], index=["A"])) result = lhs.join(rhs, rsuffix="r", how="left") expected = DataFrame( { "0": Series([td, td], index=list("AB")), "0r": Series([td, pd.NaT], index=list("AB")), } ) tm.assert_frame_equal(result, expected) def test_other_datetime_unit(self): # GH 13389 df1 = DataFrame({"entity_id": [101, 102]}) s = Series([None, None], index=[101, 102], name="days") for dtype in [ "datetime64[D]", "datetime64[h]", "datetime64[m]", "datetime64[s]", "datetime64[ms]", "datetime64[us]", "datetime64[ns]", ]: df2 = s.astype(dtype).to_frame("days") # coerces to datetime64[ns], thus should not be affected assert df2["days"].dtype == "datetime64[ns]" result = df1.merge(df2, left_on="entity_id", right_index=True) exp = DataFrame( { "entity_id": [101, 102], "days": np.array(["nat", "nat"], dtype="datetime64[ns]"), }, columns=["entity_id", "days"], ) tm.assert_frame_equal(result, exp) @pytest.mark.parametrize("unit", ["D", "h", "m", "s", "ms", "us", "ns"]) def test_other_timedelta_unit(self, unit): # GH 13389 df1 = DataFrame({"entity_id": [101, 102]}) s = Series([None, None], index=[101, 102], name="days") dtype = f"m8[{unit}]" df2 = s.astype(dtype).to_frame("days") assert df2["days"].dtype == "m8[ns]" result = df1.merge(df2, left_on="entity_id", right_index=True) exp = DataFrame( {"entity_id": [101, 102], "days": np.array(["nat", "nat"], dtype=dtype)}, columns=["entity_id", "days"], ) tm.assert_frame_equal(result, exp) def test_overlapping_columns_error_message(self): df = DataFrame({"key": [1, 2, 3], "v1": [4, 5, 6], "v2": [7, 8, 9]}) df2 = DataFrame({"key": [1, 2, 3], "v1": [4, 5, 6], "v2": [7, 8, 9]}) df.columns = ["key", "foo", "foo"] df2.columns = ["key", "bar", "bar"] expected = DataFrame( { "key": [1, 2, 3], "v1": [4, 5, 6], "v2": [7, 8, 9], "v3": [4, 5, 6], "v4": [7, 8, 9], } ) expected.columns = ["key", "foo", "foo", "bar", "bar"] tm.assert_frame_equal(merge(df, df2), expected) # #2649, #10639 df2.columns = ["key1", "foo", "foo"] msg = r"Data columns not unique: Index\(\['foo'\], dtype='object'\)" with pytest.raises(MergeError, match=msg): merge(df, df2) def test_merge_on_datetime64tz(self): # GH11405 left = DataFrame( { "key": pd.date_range("20151010", periods=2, tz="US/Eastern"), "value": [1, 2], } ) right = DataFrame( { "key": pd.date_range("20151011", periods=3, tz="US/Eastern"), "value": [1, 2, 3], } ) expected = DataFrame( { "key": pd.date_range("20151010", periods=4, tz="US/Eastern"), "value_x": [1, 2, np.nan, np.nan], "value_y": [np.nan, 1, 2, 3], } ) result = pd.merge(left, right, on="key", how="outer") tm.assert_frame_equal(result, expected) left = DataFrame( { "key": [1, 2], "value": pd.date_range("20151010", periods=2, tz="US/Eastern"), } ) right = DataFrame( { "key": [2, 3], "value": pd.date_range("20151011", periods=2, tz="US/Eastern"), } ) expected = DataFrame( { "key": [1, 2, 3], "value_x": list(pd.date_range("20151010", periods=2, tz="US/Eastern")) + [pd.NaT], "value_y": [pd.NaT] + list(pd.date_range("20151011", periods=2, tz="US/Eastern")), } ) result = pd.merge(left, right, on="key", how="outer") tm.assert_frame_equal(result, expected) assert result["value_x"].dtype == "datetime64[ns, US/Eastern]" assert result["value_y"].dtype == "datetime64[ns, US/Eastern]" def test_merge_on_datetime64tz_empty(self): # https://github.com/pandas-dev/pandas/issues/25014 dtz = pd.DatetimeTZDtype(tz="UTC") right = DataFrame( { "date": [pd.Timestamp("2018", tz=dtz.tz)], "value": [4.0], "date2": [pd.Timestamp("2019", tz=dtz.tz)], }, columns=["date", "value", "date2"], ) left = right[:0] result = left.merge(right, on="date") expected = DataFrame( { "value_x": Series(dtype=float), "date2_x": Series(dtype=dtz), "date": Series(dtype=dtz), "value_y": Series(dtype=float), "date2_y": Series(dtype=dtz), }, columns=["value_x", "date2_x", "date", "value_y", "date2_y"], ) tm.assert_frame_equal(result, expected) def test_merge_datetime64tz_with_dst_transition(self): # GH 18885 df1 = DataFrame( pd.date_range("2017-10-29 01:00", periods=4, freq="H", tz="Europe/Madrid"), columns=["date"], ) df1["value"] = 1 df2 = DataFrame( { "date": pd.to_datetime( [ "2017-10-29 03:00:00", "2017-10-29 04:00:00", "2017-10-29 05:00:00", ] ), "value": 2, } ) df2["date"] = df2["date"].dt.tz_localize("UTC").dt.tz_convert("Europe/Madrid") result = pd.merge(df1, df2, how="outer", on="date") expected = DataFrame( { "date": pd.date_range( "2017-10-29 01:00", periods=7, freq="H", tz="Europe/Madrid" ), "value_x": [1] * 4 + [np.nan] * 3, "value_y": [np.nan] * 4 + [2] * 3, } ) tm.assert_frame_equal(result, expected) def test_merge_non_unique_period_index(self): # GH #16871 index = pd.period_range("2016-01-01", periods=16, freq="M") df = DataFrame(list(range(len(index))), index=index, columns=["pnum"]) df2 = concat([df, df]) result = df.merge(df2, left_index=True, right_index=True, how="inner") expected = DataFrame( np.tile(np.arange(16, dtype=np.int64).repeat(2).reshape(-1, 1), 2), columns=["pnum_x", "pnum_y"], index=df2.sort_index().index, ) tm.assert_frame_equal(result, expected) def test_merge_on_periods(self): left = DataFrame( {"key": pd.period_range("20151010", periods=2, freq="D"), "value": [1, 2]} ) right = DataFrame( { "key": pd.period_range("20151011", periods=3, freq="D"), "value": [1, 2, 3], } ) expected = DataFrame( { "key": pd.period_range("20151010", periods=4, freq="D"), "value_x": [1, 2, np.nan, np.nan], "value_y": [np.nan, 1, 2, 3], } ) result = pd.merge(left, right, on="key", how="outer") tm.assert_frame_equal(result, expected) left = DataFrame( {"key": [1, 2], "value": pd.period_range("20151010", periods=2, freq="D")} ) right = DataFrame( {"key": [2, 3], "value": pd.period_range("20151011", periods=2, freq="D")} ) exp_x = pd.period_range("20151010", periods=2, freq="D") exp_y = pd.period_range("20151011", periods=2, freq="D") expected = DataFrame( { "key": [1, 2, 3], "value_x": list(exp_x) + [pd.NaT], "value_y": [pd.NaT] + list(exp_y), } ) result = pd.merge(left, right, on="key", how="outer") tm.assert_frame_equal(result, expected) assert result["value_x"].dtype == "Period[D]" assert result["value_y"].dtype == "Period[D]" def test_indicator(self): # PR #10054. xref #7412 and closes #8790. df1 = DataFrame( {"col1": [0, 1], "col_conflict": [1, 2], "col_left": ["a", "b"]} ) df1_copy = df1.copy() df2 = DataFrame( { "col1": [1, 2, 3, 4, 5], "col_conflict": [1, 2, 3, 4, 5], "col_right": [2, 2, 2, 2, 2], } ) df2_copy = df2.copy() df_result = DataFrame( { "col1": [0, 1, 2, 3, 4, 5], "col_conflict_x": [1, 2, np.nan, np.nan, np.nan, np.nan], "col_left": ["a", "b", np.nan, np.nan, np.nan, np.nan], "col_conflict_y": [np.nan, 1, 2, 3, 4, 5], "col_right": [np.nan, 2, 2, 2, 2, 2], } ) df_result["_merge"] = Categorical( [ "left_only", "both", "right_only", "right_only", "right_only", "right_only", ], categories=["left_only", "right_only", "both"], ) df_result = df_result[ [ "col1", "col_conflict_x", "col_left", "col_conflict_y", "col_right", "_merge", ] ] test = merge(df1, df2, on="col1", how="outer", indicator=True) tm.assert_frame_equal(test, df_result) test = df1.merge(df2, on="col1", how="outer", indicator=True) tm.assert_frame_equal(test, df_result) # No side effects tm.assert_frame_equal(df1, df1_copy) tm.assert_frame_equal(df2, df2_copy) # Check with custom name df_result_custom_name = df_result df_result_custom_name = df_result_custom_name.rename( columns={"_merge": "custom_name"} ) test_custom_name = merge( df1, df2, on="col1", how="outer", indicator="custom_name" ) tm.assert_frame_equal(test_custom_name, df_result_custom_name) test_custom_name = df1.merge( df2, on="col1", how="outer", indicator="custom_name" ) tm.assert_frame_equal(test_custom_name, df_result_custom_name) # Check only accepts strings and booleans msg = "indicator option can only accept boolean or string arguments" with pytest.raises(ValueError, match=msg): merge(df1, df2, on="col1", how="outer", indicator=5) with pytest.raises(ValueError, match=msg): df1.merge(df2, on="col1", how="outer", indicator=5) # Check result integrity test2 = merge(df1, df2, on="col1", how="left", indicator=True) assert (test2._merge != "right_only").all() test2 = df1.merge(df2, on="col1", how="left", indicator=True) assert (test2._merge != "right_only").all() test3 = merge(df1, df2, on="col1", how="right", indicator=True) assert (test3._merge != "left_only").all() test3 = df1.merge(df2, on="col1", how="right", indicator=True) assert (test3._merge != "left_only").all() test4 = merge(df1, df2, on="col1", how="inner", indicator=True) assert (test4._merge == "both").all() test4 = df1.merge(df2, on="col1", how="inner", indicator=True) assert (test4._merge == "both").all() # Check if working name in df for i in ["_right_indicator", "_left_indicator", "_merge"]: df_badcolumn = DataFrame({"col1": [1, 2], i: [2, 2]}) msg = ( "Cannot use `indicator=True` option when data contains a " f"column named {i}|" "Cannot use name of an existing column for indicator column" ) with pytest.raises(ValueError, match=msg): merge(df1, df_badcolumn, on="col1", how="outer", indicator=True) with pytest.raises(ValueError, match=msg): df1.merge(df_badcolumn, on="col1", how="outer", indicator=True) # Check for name conflict with custom name df_badcolumn = DataFrame({"col1": [1, 2], "custom_column_name": [2, 2]}) msg = "Cannot use name of an existing column for indicator column" with pytest.raises(ValueError, match=msg): merge( df1, df_badcolumn, on="col1", how="outer", indicator="custom_column_name", ) with pytest.raises(ValueError, match=msg): df1.merge( df_badcolumn, on="col1", how="outer", indicator="custom_column_name" ) # Merge on multiple columns df3 = DataFrame({"col1": [0, 1], "col2": ["a", "b"]}) df4 = DataFrame({"col1": [1, 1, 3], "col2": ["b", "x", "y"]}) hand_coded_result = DataFrame( {"col1": [0, 1, 1, 3], "col2": ["a", "b", "x", "y"]} ) hand_coded_result["_merge"] = Categorical( ["left_only", "both", "right_only", "right_only"], categories=["left_only", "right_only", "both"], ) test5 = merge(df3, df4, on=["col1", "col2"], how="outer", indicator=True) tm.assert_frame_equal(test5, hand_coded_result) test5 = df3.merge(df4, on=["col1", "col2"], how="outer", indicator=True) tm.assert_frame_equal(test5, hand_coded_result) def test_validation(self): left = DataFrame( {"a": ["a", "b", "c", "d"], "b": ["cat", "dog", "weasel", "horse"]}, index=range(4), ) right = DataFrame( { "a": ["a", "b", "c", "d", "e"], "c": ["meow", "bark", "um... weasel noise?", "nay", "chirp"], }, index=range(5), ) # Make sure no side effects. left_copy = left.copy() right_copy = right.copy() result = merge(left, right, left_index=True, right_index=True, validate="1:1") tm.assert_frame_equal(left, left_copy) tm.assert_frame_equal(right, right_copy) # make sure merge still correct expected = DataFrame( { "a_x": ["a", "b", "c", "d"], "b": ["cat", "dog", "weasel", "horse"], "a_y": ["a", "b", "c", "d"], "c": ["meow", "bark", "um... weasel noise?", "nay"], }, index=range(4), columns=["a_x", "b", "a_y", "c"], ) result = merge( left, right, left_index=True, right_index=True, validate="one_to_one" ) tm.assert_frame_equal(result, expected) expected_2 = DataFrame( { "a": ["a", "b", "c", "d"], "b": ["cat", "dog", "weasel", "horse"], "c": ["meow", "bark", "um... weasel noise?", "nay"], }, index=range(4), ) result = merge(left, right, on="a", validate="1:1") tm.assert_frame_equal(left, left_copy) tm.assert_frame_equal(right, right_copy) tm.assert_frame_equal(result, expected_2) result = merge(left, right, on="a", validate="one_to_one") tm.assert_frame_equal(result, expected_2) # One index, one column expected_3 = DataFrame( { "b": ["cat", "dog", "weasel", "horse"], "a": ["a", "b", "c", "d"], "c": ["meow", "bark", "um... weasel noise?", "nay"], }, columns=["b", "a", "c"], index=range(4), ) left_index_reset = left.set_index("a") result = merge( left_index_reset, right, left_index=True, right_on="a", validate="one_to_one", ) tm.assert_frame_equal(result, expected_3) # Dups on right right_w_dups = right.append(DataFrame({"a": ["e"], "c": ["moo"]}, index=[4])) merge( left, right_w_dups, left_index=True, right_index=True, validate="one_to_many", ) msg = "Merge keys are not unique in right dataset; not a one-to-one merge" with pytest.raises(MergeError, match=msg): merge( left, right_w_dups, left_index=True, right_index=True, validate="one_to_one", ) with pytest.raises(MergeError, match=msg): merge(left, right_w_dups, on="a", validate="one_to_one") # Dups on left left_w_dups = left.append( DataFrame({"a": ["a"], "c": ["cow"]}, index=[3]), sort=True ) merge( left_w_dups, right, left_index=True, right_index=True, validate="many_to_one", ) msg = "Merge keys are not unique in left dataset; not a one-to-one merge" with pytest.raises(MergeError, match=msg): merge( left_w_dups, right, left_index=True, right_index=True, validate="one_to_one", ) with pytest.raises(MergeError, match=msg): merge(left_w_dups, right, on="a", validate="one_to_one") # Dups on both merge(left_w_dups, right_w_dups, on="a", validate="many_to_many") msg = "Merge keys are not unique in right dataset; not a many-to-one merge" with pytest.raises(MergeError, match=msg): merge( left_w_dups, right_w_dups, left_index=True, right_index=True, validate="many_to_one", ) msg = "Merge keys are not unique in left dataset; not a one-to-many merge" with pytest.raises(MergeError, match=msg): merge(left_w_dups, right_w_dups, on="a", validate="one_to_many") # Check invalid arguments msg = "Not a valid argument for validate" with pytest.raises(ValueError, match=msg): merge(left, right, on="a", validate="jibberish") # Two column merge, dups in both, but jointly no dups. left = DataFrame( { "a": ["a", "a", "b", "b"], "b": [0, 1, 0, 1], "c": ["cat", "dog", "weasel", "horse"], }, index=range(4), ) right = DataFrame( { "a": ["a", "a", "b"], "b": [0, 1, 0], "d": ["meow", "bark", "um... weasel noise?"], }, index=range(3), ) expected_multi = DataFrame( { "a": ["a", "a", "b"], "b": [0, 1, 0], "c": ["cat", "dog", "weasel"], "d": ["meow", "bark", "um... weasel noise?"], }, index=range(3), ) msg = ( "Merge keys are not unique in either left or right dataset; " "not a one-to-one merge" ) with pytest.raises(MergeError, match=msg): merge(left, right, on="a", validate="1:1") result = merge(left, right, on=["a", "b"], validate="1:1") tm.assert_frame_equal(result, expected_multi) def test_merge_two_empty_df_no_division_error(self): # GH17776, PR #17846 a = DataFrame({"a": [], "b": [], "c": []}) with np.errstate(divide="raise"): merge(a, a, on=("a", "b")) @pytest.mark.parametrize("how", ["right", "outer"]) @pytest.mark.parametrize( "index,expected_index", [ ( CategoricalIndex([1, 2, 4]), CategoricalIndex([1, 2, 4, None, None, None]), ), ( DatetimeIndex(["2001-01-01", "2002-02-02", "2003-03-03"]), DatetimeIndex( ["2001-01-01", "2002-02-02", "2003-03-03", pd.NaT, pd.NaT, pd.NaT] ), ), (Float64Index([1, 2, 3]), Float64Index([1, 2, 3, None, None, None])), (Int64Index([1, 2, 3]), Float64Index([1, 2, 3, None, None, None])), ( IntervalIndex.from_tuples([(1, 2), (2, 3), (3, 4)]), IntervalIndex.from_tuples( [(1, 2), (2, 3), (3, 4), np.nan, np.nan, np.nan] ), ), ( PeriodIndex(["2001-01-01", "2001-01-02", "2001-01-03"], freq="D"), PeriodIndex( ["2001-01-01", "2001-01-02", "2001-01-03", pd.NaT, pd.NaT, pd.NaT], freq="D", ), ), ( TimedeltaIndex(["1d", "2d", "3d"]), TimedeltaIndex(["1d", "2d", "3d", pd.NaT, pd.NaT, pd.NaT]), ), ], ) def test_merge_on_index_with_more_values(self, how, index, expected_index): # GH 24212 # pd.merge gets [0, 1, 2, -1, -1, -1] as left_indexer, ensure that # -1 is interpreted as a missing value instead of the last element df1 = DataFrame({"a": [0, 1, 2], "key": [0, 1, 2]}, index=index) df2 = DataFrame({"b": [0, 1, 2, 3, 4, 5]}) result = df1.merge(df2, left_on="key", right_index=True, how=how) expected = DataFrame( [ [0, 0, 0], [1, 1, 1], [2, 2, 2], [np.nan, 3, 3], [np.nan, 4, 4], [np.nan, 5, 5], ], columns=["a", "key", "b"], ) expected.set_index(expected_index, inplace=True) tm.assert_frame_equal(result, expected) def test_merge_right_index_right(self): # Note: the expected output here is probably incorrect. # See https://github.com/pandas-dev/pandas/issues/17257 for more. # We include this as a regression test for GH-24897. left = DataFrame({"a": [1, 2, 3], "key": [0, 1, 1]}) right = DataFrame({"b": [1, 2, 3]}) expected = DataFrame( {"a": [1, 2, 3, None], "key": [0, 1, 1, 2], "b": [1, 2, 2, 3]}, columns=["a", "key", "b"], index=[0, 1, 2, np.nan], ) result = left.merge(right, left_on="key", right_index=True, how="right") tm.assert_frame_equal(result, expected) @pytest.mark.parametrize("how", ["left", "right"]) def test_merge_preserves_row_order(self, how): # GH 27453 left_df = DataFrame({"animal": ["dog", "pig"], "max_speed": [40, 11]}) right_df = DataFrame({"animal": ["quetzal", "pig"], "max_speed": [80, 11]}) result = left_df.merge(right_df, on=["animal", "max_speed"], how=how) if how == "right": expected = DataFrame({"animal": ["quetzal", "pig"], "max_speed": [80, 11]}) else: expected = DataFrame({"animal": ["dog", "pig"], "max_speed": [40, 11]}) tm.assert_frame_equal(result, expected) def test_merge_take_missing_values_from_index_of_other_dtype(self): # GH 24212 left = DataFrame( { "a": [1, 2, 3], "key": Categorical(["a", "a", "b"], categories=list("abc")), } ) right = DataFrame({"b": [1, 2, 3]}, index=CategoricalIndex(["a", "b", "c"])) result = left.merge(right, left_on="key", right_index=True, how="right") expected = DataFrame( { "a": [1, 2, 3, None], "key": Categorical(["a", "a", "b", "c"]), "b": [1, 1, 2, 3], }, index=[0, 1, 2, np.nan], ) expected = expected.reindex(columns=["a", "key", "b"]) tm.assert_frame_equal(result, expected) def test_merge_readonly(self): # https://github.com/pandas-dev/pandas/issues/27943 data1 = DataFrame( np.arange(20).reshape((4, 5)) + 1, columns=["a", "b", "c", "d", "e"] ) data2 = DataFrame( np.arange(20).reshape((5, 4)) + 1, columns=["a", "b", "x", "y"] ) data1._mgr.blocks[0].values.flags.writeable = False data1.merge(data2) # no error def _check_merge(x, y): for how in ["inner", "left", "outer"]: result = x.join(y, how=how) expected = merge(x.reset_index(), y.reset_index(), how=how, sort=True) expected = expected.set_index("index") # TODO check_names on merge? tm.assert_frame_equal(result, expected, check_names=False) class TestMergeDtypes: @pytest.mark.parametrize( "right_vals", [["foo", "bar"], Series(["foo", "bar"]).astype("category")] ) def test_different(self, right_vals): left = DataFrame( { "A": ["foo", "bar"], "B": Series(["foo", "bar"]).astype("category"), "C": [1, 2], "D": [1.0, 2.0], "E": Series([1, 2], dtype="uint64"), "F": Series([1, 2], dtype="int32"), } ) right = DataFrame({"A": right_vals}) # GH 9780 # We allow merging on object and categorical cols and cast # categorical cols to object result = pd.merge(left, right, on="A") assert is_object_dtype(result.A.dtype) @pytest.mark.parametrize("d1", [np.int64, np.int32, np.int16, np.int8, np.uint8]) @pytest.mark.parametrize("d2", [np.int64, np.float64, np.float32, np.float16]) def test_join_multi_dtypes(self, d1, d2): dtype1 = np.dtype(d1) dtype2 = np.dtype(d2) left = DataFrame( { "k1": np.array([0, 1, 2] * 8, dtype=dtype1), "k2": ["foo", "bar"] * 12, "v": np.array(np.arange(24), dtype=np.int64), } ) index = MultiIndex.from_tuples([(2, "bar"), (1, "foo")]) right = DataFrame({"v2": np.array([5, 7], dtype=dtype2)}, index=index) result = left.join(right, on=["k1", "k2"]) expected = left.copy() if dtype2.kind == "i": dtype2 = np.dtype("float64") expected["v2"] = np.array(np.nan, dtype=dtype2) expected.loc[(expected.k1 == 2) & (expected.k2 == "bar"), "v2"] = 5 expected.loc[(expected.k1 == 1) & (expected.k2 == "foo"), "v2"] = 7 tm.assert_frame_equal(result, expected) result = left.join(right, on=["k1", "k2"], sort=True) expected.sort_values(["k1", "k2"], kind="mergesort", inplace=True) tm.assert_frame_equal(result, expected) @pytest.mark.parametrize( "int_vals, float_vals, exp_vals", [ ([1, 2, 3], [1.0, 2.0, 3.0], {"X": [1, 2, 3], "Y": [1.0, 2.0, 3.0]}), ([1, 2, 3], [1.0, 3.0], {"X": [1, 3], "Y": [1.0, 3.0]}), ([1, 2], [1.0, 2.0, 3.0], {"X": [1, 2], "Y": [1.0, 2.0]}), ], ) def test_merge_on_ints_floats(self, int_vals, float_vals, exp_vals): # GH 16572 # Check that float column is not cast to object if # merging on float and int columns A = DataFrame({"X": int_vals}) B = DataFrame({"Y": float_vals}) expected = DataFrame(exp_vals) result = A.merge(B, left_on="X", right_on="Y") tm.assert_frame_equal(result, expected) result = B.merge(A, left_on="Y", right_on="X") tm.assert_frame_equal(result, expected[["Y", "X"]]) def test_merge_key_dtype_cast(self): # GH 17044 df1 = DataFrame({"key": [1.0, 2.0], "v1": [10, 20]}, columns=["key", "v1"]) df2 = DataFrame({"key": [2], "v2": [200]}, columns=["key", "v2"]) result = df1.merge(df2, on="key", how="left") expected = DataFrame( {"key": [1.0, 2.0], "v1": [10, 20], "v2": [np.nan, 200.0]}, columns=["key", "v1", "v2"], ) tm.assert_frame_equal(result, expected) def test_merge_on_ints_floats_warning(self): # GH 16572 # merge will produce a warning when merging on int and # float columns where the float values are not exactly # equal to their int representation A = DataFrame({"X": [1, 2, 3]}) B = DataFrame({"Y": [1.1, 2.5, 3.0]}) expected = DataFrame({"X": [3], "Y": [3.0]}) with tm.assert_produces_warning(UserWarning): result = A.merge(B, left_on="X", right_on="Y") tm.assert_frame_equal(result, expected) with tm.assert_produces_warning(UserWarning): result = B.merge(A, left_on="Y", right_on="X") tm.assert_frame_equal(result, expected[["Y", "X"]]) # test no warning if float has NaNs B = DataFrame({"Y": [np.nan, np.nan, 3.0]}) with tm.assert_produces_warning(None): result = B.merge(A, left_on="Y", right_on="X") tm.assert_frame_equal(result, expected[["Y", "X"]]) def test_merge_incompat_infer_boolean_object(self): # GH21119: bool + object bool merge OK df1 = DataFrame({"key": Series([True, False], dtype=object)}) df2 = DataFrame({"key": [True, False]}) expected = DataFrame({"key": [True, False]}, dtype=object) result = pd.merge(df1, df2, on="key") tm.assert_frame_equal(result, expected) result = pd.merge(df2, df1, on="key") tm.assert_frame_equal(result, expected) # with missing value df1 = DataFrame({"key": Series([True, False, np.nan], dtype=object)}) df2 = DataFrame({"key": [True, False]}) expected = DataFrame({"key": [True, False]}, dtype=object) result = pd.merge(df1, df2, on="key") tm.assert_frame_equal(result, expected) result = pd.merge(df2, df1, on="key") tm.assert_frame_equal(result, expected) @pytest.mark.parametrize( "df1_vals, df2_vals", [ # merge on category coerces to object ([0, 1, 2], Series(["a", "b", "a"]).astype("category")), ([0.0, 1.0, 2.0], Series(["a", "b", "a"]).astype("category")), # no not infer ([0, 1], Series([False, True], dtype=object)), ([0, 1], Series([False, True], dtype=bool)), ], ) def test_merge_incompat_dtypes_are_ok(self, df1_vals, df2_vals): # these are explicitly allowed incompat merges, that pass thru # the result type is dependent on if the values on the rhs are # inferred, otherwise these will be coerced to object df1 = DataFrame({"A": df1_vals}) df2 = DataFrame({"A": df2_vals}) result = pd.merge(df1, df2, on=["A"]) assert is_object_dtype(result.A.dtype) result = pd.merge(df2, df1, on=["A"]) assert is_object_dtype(result.A.dtype) @pytest.mark.parametrize( "df1_vals, df2_vals", [ # do not infer to numeric (Series([1, 2], dtype="uint64"), ["a", "b", "c"]), (Series([1, 2], dtype="int32"), ["a", "b", "c"]), ([0, 1, 2], ["0", "1", "2"]), ([0.0, 1.0, 2.0], ["0", "1", "2"]), ([0, 1, 2], ["0", "1", "2"]), ( pd.date_range("1/1/2011", periods=2, freq="D"), ["2011-01-01", "2011-01-02"], ), (pd.date_range("1/1/2011", periods=2, freq="D"), [0, 1]), (pd.date_range("1/1/2011", periods=2, freq="D"), [0.0, 1.0]), ( pd.date_range("20130101", periods=3), pd.date_range("20130101", periods=3, tz="US/Eastern"), ), ], ) def test_merge_incompat_dtypes_error(self, df1_vals, df2_vals): # GH 9780, GH 15800 # Raise a ValueError when a user tries to merge on # dtypes that are incompatible (e.g., obj and int/float) df1 = DataFrame({"A": df1_vals}) df2 = DataFrame({"A": df2_vals}) msg = ( f"You are trying to merge on {df1['A'].dtype} and " f"{df2['A'].dtype} columns. If you wish to proceed " "you should use pd.concat" ) msg = re.escape(msg) with pytest.raises(ValueError, match=msg): pd.merge(df1, df2, on=["A"]) # Check that error still raised when swapping order of dataframes msg = ( f"You are trying to merge on {df2['A'].dtype} and " f"{df1['A'].dtype} columns. If you wish to proceed " "you should use pd.concat" ) msg = re.escape(msg) with pytest.raises(ValueError, match=msg): pd.merge(df2, df1, on=["A"]) @pytest.fixture def left(): np.random.seed(1234) return DataFrame( { "X": Series(np.random.choice(["foo", "bar"], size=(10,))).astype( CDT(["foo", "bar"]) ), "Y": np.random.choice(["one", "two", "three"], size=(10,)), } ) @pytest.fixture def right(): np.random.seed(1234) return DataFrame( {"X": Series(["foo", "bar"]).astype(CDT(["foo", "bar"])), "Z": [1, 2]} ) class TestMergeCategorical: def test_identical(self, left): # merging on the same, should preserve dtypes merged = pd.merge(left, left, on="X") result = merged.dtypes.sort_index() expected = Series( [CategoricalDtype(), np.dtype("O"), np.dtype("O")], index=["X", "Y_x", "Y_y"], ) tm.assert_series_equal(result, expected) def test_basic(self, left, right): # we have matching Categorical dtypes in X # so should preserve the merged column merged = pd.merge(left, right, on="X") result = merged.dtypes.sort_index() expected = Series( [CategoricalDtype(), np.dtype("O"), np.dtype("int64")], index=["X", "Y", "Z"], ) tm.assert_series_equal(result, expected) def test_merge_categorical(self): # GH 9426 right = DataFrame( { "c": {0: "a", 1: "b", 2: "c", 3: "d", 4: "e"}, "d": {0: "null", 1: "null", 2: "null", 3: "null", 4: "null"}, } ) left = DataFrame( { "a": {0: "f", 1: "f", 2: "f", 3: "f", 4: "f"}, "b": {0: "g", 1: "g", 2: "g", 3: "g", 4: "g"}, } ) df = pd.merge(left, right, how="left", left_on="b", right_on="c") # object-object expected = df.copy() # object-cat # note that we propagate the category # because we don't have any matching rows cright = right.copy() cright["d"] = cright["d"].astype("category") result = pd.merge(left, cright, how="left", left_on="b", right_on="c") expected["d"] = expected["d"].astype(CategoricalDtype(["null"])) tm.assert_frame_equal(result, expected) # cat-object cleft = left.copy() cleft["b"] = cleft["b"].astype("category") result = pd.merge(cleft, cright, how="left", left_on="b", right_on="c") tm.assert_frame_equal(result, expected) # cat-cat cright = right.copy() cright["d"] = cright["d"].astype("category") cleft = left.copy() cleft["b"] = cleft["b"].astype("category") result = pd.merge(cleft, cright, how="left", left_on="b", right_on="c") tm.assert_frame_equal(result, expected) def tests_merge_categorical_unordered_equal(self): # GH-19551 df1 = DataFrame( { "Foo": Categorical(["A", "B", "C"], categories=["A", "B", "C"]), "Left": ["A0", "B0", "C0"], } ) df2 = DataFrame( { "Foo": Categorical(["C", "B", "A"], categories=["C", "B", "A"]), "Right": ["C1", "B1", "A1"], } ) result = pd.merge(df1, df2, on=["Foo"]) expected = DataFrame( { "Foo": Categorical(["A", "B", "C"]), "Left": ["A0", "B0", "C0"], "Right": ["A1", "B1", "C1"], } ) tm.assert_frame_equal(result, expected) def test_other_columns(self, left, right): # non-merge columns should preserve if possible right = right.assign(Z=right.Z.astype("category")) merged = pd.merge(left, right, on="X") result = merged.dtypes.sort_index() expected = Series( [CategoricalDtype(), np.dtype("O"), CategoricalDtype()], index=["X", "Y", "Z"], ) tm.assert_series_equal(result, expected) # categories are preserved assert left.X.values._categories_match_up_to_permutation(merged.X.values) assert right.Z.values._categories_match_up_to_permutation(merged.Z.values) @pytest.mark.parametrize( "change", [ lambda x: x, lambda x: x.astype(CDT(["foo", "bar", "bah"])), lambda x: x.astype(CDT(ordered=True)), ], ) def test_dtype_on_merged_different(self, change, join_type, left, right): # our merging columns, X now has 2 different dtypes # so we must be object as a result X = change(right.X.astype("object")) right = right.assign(X=X) assert is_categorical_dtype(left.X.values.dtype) # assert not left.X.values._categories_match_up_to_permutation(right.X.values) merged = pd.merge(left, right, on="X", how=join_type) result = merged.dtypes.sort_index() expected = Series( [np.dtype("O"), np.dtype("O"), np.dtype("int64")], index=["X", "Y", "Z"] ) tm.assert_series_equal(result, expected) def test_self_join_multiple_categories(self): # GH 16767 # non-duplicates should work with multiple categories m = 5 df = DataFrame( { "a": ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j"] * m, "b": ["t", "w", "x", "y", "z"] * 2 * m, "c": [ letter for each in ["m", "n", "u", "p", "o"] for letter in [each] * 2 * m ], "d": [ letter for each in [ "aa", "bb", "cc", "dd", "ee", "ff", "gg", "hh", "ii", "jj", ] for letter in [each] * m ], } ) # change them all to categorical variables df = df.apply(lambda x: x.astype("category")) # self-join should equal ourselves result = pd.merge(df, df, on=list(df.columns)) tm.assert_frame_equal(result, df) def test_dtype_on_categorical_dates(self): # GH 16900 # dates should not be coerced to ints df = DataFrame( [[date(2001, 1, 1), 1.1], [date(2001, 1, 2), 1.3]], columns=["date", "num2"] ) df["date"] = df["date"].astype("category") df2 = DataFrame( [[date(2001, 1, 1), 1.3], [date(2001, 1, 3), 1.4]], columns=["date", "num4"] ) df2["date"] = df2["date"].astype("category") expected_outer = DataFrame( [ [pd.Timestamp("2001-01-01"), 1.1, 1.3], [pd.Timestamp("2001-01-02"), 1.3, np.nan], [pd.Timestamp("2001-01-03"), np.nan, 1.4], ], columns=["date", "num2", "num4"], ) result_outer = pd.merge(df, df2, how="outer", on=["date"]) tm.assert_frame_equal(result_outer, expected_outer) expected_inner = DataFrame( [[pd.Timestamp("2001-01-01"), 1.1, 1.3]], columns=["date", "num2", "num4"] ) result_inner = pd.merge(df, df2, how="inner", on=["date"]) tm.assert_frame_equal(result_inner, expected_inner) @pytest.mark.parametrize("ordered", [True, False]) @pytest.mark.parametrize( "category_column,categories,expected_categories", [ ([False, True, True, False], [True, False], [True, False]), ([2, 1, 1, 2], [1, 2], [1, 2]), (["False", "True", "True", "False"], ["True", "False"], ["True", "False"]), ], ) def test_merging_with_bool_or_int_cateorical_column( self, category_column, categories, expected_categories, ordered ): # GH 17187 # merging with a boolean/int categorical column df1 = DataFrame({"id": [1, 2, 3, 4], "cat": category_column}) df1["cat"] = df1["cat"].astype(CDT(categories, ordered=ordered)) df2 = DataFrame({"id": [2, 4], "num": [1, 9]}) result = df1.merge(df2) expected = DataFrame({"id": [2, 4], "cat": expected_categories, "num": [1, 9]}) expected["cat"] = expected["cat"].astype(CDT(categories, ordered=ordered)) tm.assert_frame_equal(expected, result) def test_merge_on_int_array(self): # GH 23020 df = DataFrame({"A": Series([1, 2, np.nan], dtype="Int64"), "B": 1}) result = pd.merge(df, df, on="A") expected = DataFrame( {"A": Series([1, 2, np.nan], dtype="Int64"), "B_x": 1, "B_y": 1} ) tm.assert_frame_equal(result, expected) @pytest.fixture def left_df(): return DataFrame({"a": [20, 10, 0]}, index=[2, 1, 0]) @pytest.fixture def right_df(): return DataFrame({"b": [300, 100, 200]}, index=[3, 1, 2]) class TestMergeOnIndexes: @pytest.mark.parametrize( "how, sort, expected", [ ("inner", False, DataFrame({"a": [20, 10], "b": [200, 100]}, index=[2, 1])), ("inner", True, DataFrame({"a": [10, 20], "b": [100, 200]}, index=[1, 2])), ( "left", False, DataFrame({"a": [20, 10, 0], "b": [200, 100, np.nan]}, index=[2, 1, 0]), ), ( "left", True, DataFrame({"a": [0, 10, 20], "b": [np.nan, 100, 200]}, index=[0, 1, 2]), ), ( "right", False, DataFrame( {"a": [np.nan, 10, 20], "b": [300, 100, 200]}, index=[3, 1, 2] ), ), ( "right", True, DataFrame( {"a": [10, 20, np.nan], "b": [100, 200, 300]}, index=[1, 2, 3] ), ), ( "outer", False, DataFrame( {"a": [0, 10, 20, np.nan], "b": [np.nan, 100, 200, 300]}, index=[0, 1, 2, 3], ), ), ( "outer", True, DataFrame( {"a": [0, 10, 20, np.nan], "b": [np.nan, 100, 200, 300]}, index=[0, 1, 2, 3], ), ), ], ) def test_merge_on_indexes(self, left_df, right_df, how, sort, expected): result = pd.merge( left_df, right_df, left_index=True, right_index=True, how=how, sort=sort ) tm.assert_frame_equal(result, expected) @pytest.mark.parametrize( "index", [ CategoricalIndex(["A", "B"], categories=["A", "B"], name="index_col"), Float64Index([1.0, 2.0], name="index_col"), Int64Index([1, 2], name="index_col"), UInt64Index([1, 2], name="index_col"), RangeIndex(start=0, stop=2, name="index_col"), DatetimeIndex(["2018-01-01", "2018-01-02"], name="index_col"), ], ids=lambda x: type(x).__name__, ) def test_merge_index_types(index): # gh-20777 # assert key access is consistent across index types left = DataFrame({"left_data": [1, 2]}, index=index) right = DataFrame({"right_data": [1.0, 2.0]}, index=index) result = left.merge(right, on=["index_col"]) expected = DataFrame({"left_data": [1, 2], "right_data": [1.0, 2.0]}, index=index) tm.assert_frame_equal(result, expected) @pytest.mark.parametrize( "on,left_on,right_on,left_index,right_index,nm", [ (["outer", "inner"], None, None, False, False, "B"), (None, None, None, True, True, "B"), (None, ["outer", "inner"], None, False, True, "B"), (None, None, ["outer", "inner"], True, False, "B"), (["outer", "inner"], None, None, False, False, None), (None, None, None, True, True, None), (None, ["outer", "inner"], None, False, True, None), (None, None, ["outer", "inner"], True, False, None), ], ) def test_merge_series(on, left_on, right_on, left_index, right_index, nm): # GH 21220 a = DataFrame( {"A": [1, 2, 3, 4]}, index=pd.MultiIndex.from_product( [["a", "b"], [0, 1]], names=["outer", "inner"] ), ) b = Series( [1, 2, 3, 4], index=pd.MultiIndex.from_product( [["a", "b"], [1, 2]], names=["outer", "inner"] ), name=nm, ) expected = DataFrame( {"A": [2, 4], "B": [1, 3]}, index=pd.MultiIndex.from_product([["a", "b"], [1]], names=["outer", "inner"]), ) if nm is not None: result = pd.merge( a, b, on=on, left_on=left_on, right_on=right_on, left_index=left_index, right_index=right_index, ) tm.assert_frame_equal(result, expected) else: msg = "Cannot merge a Series without a name" with pytest.raises(ValueError, match=msg): result = pd.merge( a, b, on=on, left_on=left_on, right_on=right_on, left_index=left_index, right_index=right_index, ) @pytest.mark.parametrize( "col1, col2, kwargs, expected_cols", [ (0, 0, {"suffixes": ("", "_dup")}, ["0", "0_dup"]), (0, 0, {"suffixes": (None, "_dup")}, [0, "0_dup"]), (0, 0, {"suffixes": ("_x", "_y")}, ["0_x", "0_y"]), (0, 0, {"suffixes": ["_x", "_y"]}, ["0_x", "0_y"]), ("a", 0, {"suffixes": (None, "_y")}, ["a", 0]), (0.0, 0.0, {"suffixes": ("_x", None)}, ["0.0_x", 0.0]), ("b", "b", {"suffixes": (None, "_y")}, ["b", "b_y"]), ("a", "a", {"suffixes": ("_x", None)}, ["a_x", "a"]), ("a", "b", {"suffixes": ("_x", None)}, ["a", "b"]), ("a", "a", {"suffixes": (None, "_x")}, ["a", "a_x"]), (0, 0, {"suffixes": ("_a", None)}, ["0_a", 0]), ("a", "a", {}, ["a_x", "a_y"]), (0, 0, {}, ["0_x", "0_y"]), ], ) def test_merge_suffix(col1, col2, kwargs, expected_cols): # issue: 24782 a = DataFrame({col1: [1, 2, 3]}) b = DataFrame({col2: [4, 5, 6]}) expected = DataFrame([[1, 4], [2, 5], [3, 6]], columns=expected_cols) result = a.merge(b, left_index=True, right_index=True, **kwargs) tm.assert_frame_equal(result, expected) result = pd.merge(a, b, left_index=True, right_index=True, **kwargs) tm.assert_frame_equal(result, expected) @pytest.mark.parametrize( "how,expected", [ ( "right", DataFrame( {"A": [100, 200, 300], "B1": [60, 70, np.nan], "B2": [600, 700, 800]} ), ), ( "outer", DataFrame( { "A": [100, 200, 1, 300], "B1": [60, 70, 80, np.nan], "B2": [600, 700, np.nan, 800], } ), ), ], ) def test_merge_duplicate_suffix(how, expected): left_df = DataFrame({"A": [100, 200, 1], "B": [60, 70, 80]}) right_df = DataFrame({"A": [100, 200, 300], "B": [600, 700, 800]}) result = merge(left_df, right_df, on="A", how=how, suffixes=("_x", "_x")) expected.columns = ["A", "B_x", "B_x"] tm.assert_frame_equal(result, expected) @pytest.mark.parametrize( "col1, col2, suffixes", [("a", "a", (None, None)), ("a", "a", ("", None)), (0, 0, (None, ""))], ) def test_merge_suffix_error(col1, col2, suffixes): # issue: 24782 a = DataFrame({col1: [1, 2, 3]}) b = DataFrame({col2: [3, 4, 5]}) # TODO: might reconsider current raise behaviour, see issue 24782 msg = "columns overlap but no suffix specified" with pytest.raises(ValueError, match=msg): pd.merge(a, b, left_index=True, right_index=True, suffixes=suffixes) @pytest.mark.parametrize("suffixes", [{"left", "right"}, {"left": 0, "right": 0}]) def test_merge_suffix_warns(suffixes): a = DataFrame({"a": [1, 2, 3]}) b = DataFrame({"b": [3, 4, 5]}) with tm.assert_produces_warning(FutureWarning): pd.merge(a, b, left_index=True, right_index=True, suffixes={"left", "right"}) @pytest.mark.parametrize( "col1, col2, suffixes, msg", [ ("a", "a", ("a", "b", "c"), r"too many values to unpack \(expected 2\)"), ("a", "a", tuple("a"), r"not enough values to unpack \(expected 2, got 1\)"), ], ) def test_merge_suffix_length_error(col1, col2, suffixes, msg): a = DataFrame({col1: [1, 2, 3]}) b = DataFrame({col2: [3, 4, 5]}) with pytest.raises(ValueError, match=msg): pd.merge(a, b, left_index=True, right_index=True, suffixes=suffixes) @pytest.mark.parametrize("cat_dtype", ["one", "two"]) @pytest.mark.parametrize("reverse", [True, False]) def test_merge_equal_cat_dtypes(cat_dtype, reverse): # see gh-22501 cat_dtypes = { "one": CategoricalDtype(categories=["a", "b", "c"], ordered=False), "two": CategoricalDtype(categories=["a", "b", "c"], ordered=False), } df1 = DataFrame( {"foo": Series(["a", "b", "c"]).astype(cat_dtypes["one"]), "left": [1, 2, 3]} ).set_index("foo") data_foo = ["a", "b", "c"] data_right = [1, 2, 3] if reverse: data_foo.reverse() data_right.reverse() df2 = DataFrame( {"foo": Series(data_foo).astype(cat_dtypes[cat_dtype]), "right": data_right} ).set_index("foo") result = df1.merge(df2, left_index=True, right_index=True) expected = DataFrame( { "left": [1, 2, 3], "right": [1, 2, 3], "foo": Series(["a", "b", "c"]).astype(cat_dtypes["one"]), } ).set_index("foo") tm.assert_frame_equal(result, expected) def test_merge_equal_cat_dtypes2(): # see gh-22501 cat_dtype = CategoricalDtype(categories=["a", "b", "c"], ordered=False) # Test Data df1 = DataFrame( {"foo": Series(["a", "b"]).astype(cat_dtype), "left": [1, 2]} ).set_index("foo") df2 = DataFrame( {"foo": Series(["a", "b", "c"]).astype(cat_dtype), "right": [3, 2, 1]} ).set_index("foo") result = df1.merge(df2, left_index=True, right_index=True) expected = DataFrame( {"left": [1, 2], "right": [3, 2], "foo": Series(["a", "b"]).astype(cat_dtype)} ).set_index("foo") tm.assert_frame_equal(result, expected) def test_merge_on_cat_and_ext_array(): # GH 28668 right = DataFrame( {"a": Series([pd.Interval(0, 1), pd.Interval(1, 2)], dtype="interval")} ) left = right.copy() left["a"] = left["a"].astype("category") result = pd.merge(left, right, how="inner", on="a") expected = right.copy() tm.assert_frame_equal(result, expected) def test_merge_multiindex_columns(): # Issue #28518 # Verify that merging two dataframes give the expected labels # The original cause of this issue come from a bug lexsort_depth and is tested in # test_lexsort_depth letters = ["a", "b", "c", "d"] numbers = ["1", "2", "3"] index = pd.MultiIndex.from_product((letters, numbers), names=["outer", "inner"]) frame_x = DataFrame(columns=index) frame_x["id"] = "" frame_y = DataFrame(columns=index) frame_y["id"] = "" l_suf = "_x" r_suf = "_y" result = frame_x.merge(frame_y, on="id", suffixes=((l_suf, r_suf))) # Constructing the expected results expected_labels = [letter + l_suf for letter in letters] + [ letter + r_suf for letter in letters ] expected_index = pd.MultiIndex.from_product( [expected_labels, numbers], names=["outer", "inner"] ) expected = DataFrame(columns=expected_index) expected["id"] = "" tm.assert_frame_equal(result, expected) def test_merge_datetime_upcast_dtype(): # https://github.com/pandas-dev/pandas/issues/31208 df1 = DataFrame({"x": ["a", "b", "c"], "y": ["1", "2", "4"]}) df2 = DataFrame( {"y": ["1", "2", "3"], "z": pd.to_datetime(["2000", "2001", "2002"])} ) result = pd.merge(df1, df2, how="left", on="y") expected = DataFrame( { "x": ["a", "b", "c"], "y": ["1", "2", "4"], "z": pd.to_datetime(["2000", "2001", "NaT"]), } ) tm.assert_frame_equal(result, expected) @pytest.mark.parametrize("n_categories", [5, 128]) def test_categorical_non_unique_monotonic(n_categories): # GH 28189 # With n_categories as 5, we test the int8 case is hit in libjoin, # with n_categories as 128 we test the int16 case. left_index = CategoricalIndex([0] + list(range(n_categories))) df1 = DataFrame(range(n_categories + 1), columns=["value"], index=left_index) df2 = DataFrame( [[6]], columns=["value"], index=CategoricalIndex([0], categories=np.arange(n_categories)), ) result = merge(df1, df2, how="left", left_index=True, right_index=True) expected = DataFrame( [[i, 6.0] if i < 2 else [i, np.nan] for i in range(n_categories + 1)], columns=["value_x", "value_y"], index=left_index, ) tm.assert_frame_equal(expected, result) def test_merge_join_categorical_multiindex(): # From issue 16627 a = { "Cat1": Categorical(["a", "b", "a", "c", "a", "b"], ["a", "b", "c"]), "Int1": [0, 1, 0, 1, 0, 0], } a = DataFrame(a) b = { "Cat": Categorical(["a", "b", "c", "a", "b", "c"], ["a", "b", "c"]), "Int": [0, 0, 0, 1, 1, 1], "Factor": [1.1, 1.2, 1.3, 1.4, 1.5, 1.6], } b = DataFrame(b).set_index(["Cat", "Int"])["Factor"] expected = merge( a, b.reset_index(), left_on=["Cat1", "Int1"], right_on=["Cat", "Int"], how="left", ) expected = expected.drop(["Cat", "Int"], axis=1) result = a.join(b, on=["Cat1", "Int1"]) tm.assert_frame_equal(expected, result) # Same test, but with ordered categorical a = { "Cat1": Categorical( ["a", "b", "a", "c", "a", "b"], ["b", "a", "c"], ordered=True ), "Int1": [0, 1, 0, 1, 0, 0], } a = DataFrame(a) b = { "Cat": Categorical( ["a", "b", "c", "a", "b", "c"], ["b", "a", "c"], ordered=True ), "Int": [0, 0, 0, 1, 1, 1], "Factor": [1.1, 1.2, 1.3, 1.4, 1.5, 1.6], } b = DataFrame(b).set_index(["Cat", "Int"])["Factor"] expected = merge( a, b.reset_index(), left_on=["Cat1", "Int1"], right_on=["Cat", "Int"], how="left", ) expected = expected.drop(["Cat", "Int"], axis=1) result = a.join(b, on=["Cat1", "Int1"]) tm.assert_frame_equal(expected, result) @pytest.mark.parametrize("func", ["merge", "merge_asof"]) @pytest.mark.parametrize( ("kwargs", "err_msg"), [ ({"left_on": "a", "left_index": True}, ["left_on", "left_index"]), ({"right_on": "a", "right_index": True}, ["right_on", "right_index"]), ], ) def test_merge_join_cols_error_reporting_duplicates(func, kwargs, err_msg): # GH: 16228 left = DataFrame({"a": [1, 2], "b": [3, 4]}) right = DataFrame({"a": [1, 1], "c": [5, 6]}) msg = rf'Can only pass argument "{err_msg[0]}" OR "{err_msg[1]}" not both\.' with pytest.raises(MergeError, match=msg): getattr(pd, func)(left, right, **kwargs) @pytest.mark.parametrize("func", ["merge", "merge_asof"]) @pytest.mark.parametrize( ("kwargs", "err_msg"), [ ({"left_on": "a"}, ["right_on", "right_index"]), ({"right_on": "a"}, ["left_on", "left_index"]), ], ) def test_merge_join_cols_error_reporting_missing(func, kwargs, err_msg): # GH: 16228 left = DataFrame({"a": [1, 2], "b": [3, 4]}) right = DataFrame({"a": [1, 1], "c": [5, 6]}) msg = rf'Must pass "{err_msg[0]}" OR "{err_msg[1]}"\.' with pytest.raises(MergeError, match=msg): getattr(pd, func)(left, right, **kwargs) @pytest.mark.parametrize("func", ["merge", "merge_asof"]) @pytest.mark.parametrize( "kwargs", [ {"right_index": True}, {"left_index": True}, ], ) def test_merge_join_cols_error_reporting_on_and_index(func, kwargs): # GH: 16228 left = DataFrame({"a": [1, 2], "b": [3, 4]}) right = DataFrame({"a": [1, 1], "c": [5, 6]}) msg = ( r'Can only pass argument "on" OR "left_index" ' r'and "right_index", not a combination of both\.' ) with pytest.raises(MergeError, match=msg): getattr(pd, func)(left, right, on="a", **kwargs) def test_merge_right_left_index(): # GH#38616 left = DataFrame({"x": [1, 1], "z": ["foo", "foo"]}) right = DataFrame({"x": [1, 1], "z": ["foo", "foo"]}) result = pd.merge(left, right, how="right", left_index=True, right_on="x") expected = DataFrame( { "x": [1, 1], "x_x": [1, 1], "z_x": ["foo", "foo"], "x_y": [1, 1], "z_y": ["foo", "foo"], } ) tm.assert_frame_equal(result, expected)