""" Tests that the specified index column (a.k.a "index_col") is properly handled or inferred during parsing for all of the parsers defined in parsers.py """ from io import StringIO import numpy as np import pytest from pandas import DataFrame, Index, MultiIndex import pandas._testing as tm @pytest.mark.parametrize("with_header", [True, False]) def test_index_col_named(all_parsers, with_header): parser = all_parsers no_header = """\ KORD1,19990127, 19:00:00, 18:56:00, 0.8100, 2.8100, 7.2000, 0.0000, 280.0000 KORD2,19990127, 20:00:00, 19:56:00, 0.0100, 2.2100, 7.2000, 0.0000, 260.0000 KORD3,19990127, 21:00:00, 20:56:00, -0.5900, 2.2100, 5.7000, 0.0000, 280.0000 KORD4,19990127, 21:00:00, 21:18:00, -0.9900, 2.0100, 3.6000, 0.0000, 270.0000 KORD5,19990127, 22:00:00, 21:56:00, -0.5900, 1.7100, 5.1000, 0.0000, 290.0000 KORD6,19990127, 23:00:00, 22:56:00, -0.5900, 1.7100, 4.6000, 0.0000, 280.0000""" header = "ID,date,NominalTime,ActualTime,TDew,TAir,Windspeed,Precip,WindDir\n" if with_header: data = header + no_header result = parser.read_csv(StringIO(data), index_col="ID") expected = parser.read_csv(StringIO(data), header=0).set_index("ID") tm.assert_frame_equal(result, expected) else: data = no_header msg = "Index ID invalid" with pytest.raises(ValueError, match=msg): parser.read_csv(StringIO(data), index_col="ID") def test_index_col_named2(all_parsers): parser = all_parsers data = """\ 1,2,3,4,hello 5,6,7,8,world 9,10,11,12,foo """ expected = DataFrame( {"a": [1, 5, 9], "b": [2, 6, 10], "c": [3, 7, 11], "d": [4, 8, 12]}, index=Index(["hello", "world", "foo"], name="message"), ) names = ["a", "b", "c", "d", "message"] result = parser.read_csv(StringIO(data), names=names, index_col=["message"]) tm.assert_frame_equal(result, expected) def test_index_col_is_true(all_parsers): # see gh-9798 data = "a,b\n1,2" parser = all_parsers msg = "The value of index_col couldn't be 'True'" with pytest.raises(ValueError, match=msg): parser.read_csv(StringIO(data), index_col=True) def test_infer_index_col(all_parsers): data = """A,B,C foo,1,2,3 bar,4,5,6 baz,7,8,9 """ parser = all_parsers result = parser.read_csv(StringIO(data)) expected = DataFrame( [[1, 2, 3], [4, 5, 6], [7, 8, 9]], index=["foo", "bar", "baz"], columns=["A", "B", "C"], ) tm.assert_frame_equal(result, expected) @pytest.mark.parametrize( "index_col,kwargs", [ (None, dict(columns=["x", "y", "z"])), (False, dict(columns=["x", "y", "z"])), (0, dict(columns=["y", "z"], index=Index([], name="x"))), (1, dict(columns=["x", "z"], index=Index([], name="y"))), ("x", dict(columns=["y", "z"], index=Index([], name="x"))), ("y", dict(columns=["x", "z"], index=Index([], name="y"))), ( [0, 1], dict( columns=["z"], index=MultiIndex.from_arrays([[]] * 2, names=["x", "y"]) ), ), ( ["x", "y"], dict( columns=["z"], index=MultiIndex.from_arrays([[]] * 2, names=["x", "y"]) ), ), ( [1, 0], dict( columns=["z"], index=MultiIndex.from_arrays([[]] * 2, names=["y", "x"]) ), ), ( ["y", "x"], dict( columns=["z"], index=MultiIndex.from_arrays([[]] * 2, names=["y", "x"]) ), ), ], ) def test_index_col_empty_data(all_parsers, index_col, kwargs): data = "x,y,z" parser = all_parsers result = parser.read_csv(StringIO(data), index_col=index_col) expected = DataFrame(**kwargs) tm.assert_frame_equal(result, expected) def test_empty_with_index_col_false(all_parsers): # see gh-10413 data = "x,y" parser = all_parsers result = parser.read_csv(StringIO(data), index_col=False) expected = DataFrame(columns=["x", "y"]) tm.assert_frame_equal(result, expected) @pytest.mark.parametrize( "index_names", [ ["", ""], ["foo", ""], ["", "bar"], ["foo", "bar"], ["NotReallyUnnamed", "Unnamed: 0"], ], ) def test_multi_index_naming(all_parsers, index_names): parser = all_parsers # We don't want empty index names being replaced with "Unnamed: 0" data = ",".join(index_names + ["col\na,c,1\na,d,2\nb,c,3\nb,d,4"]) result = parser.read_csv(StringIO(data), index_col=[0, 1]) expected = DataFrame( {"col": [1, 2, 3, 4]}, index=MultiIndex.from_product([["a", "b"], ["c", "d"]]) ) expected.index.names = [name if name else None for name in index_names] tm.assert_frame_equal(result, expected) def test_multi_index_naming_not_all_at_beginning(all_parsers): parser = all_parsers data = ",Unnamed: 2,\na,c,1\na,d,2\nb,c,3\nb,d,4" result = parser.read_csv(StringIO(data), index_col=[0, 2]) expected = DataFrame( {"Unnamed: 2": ["c", "d", "c", "d"]}, index=MultiIndex( levels=[["a", "b"], [1, 2, 3, 4]], codes=[[0, 0, 1, 1], [0, 1, 2, 3]] ), ) tm.assert_frame_equal(result, expected) def test_no_multi_index_level_names_empty(all_parsers): # GH 10984 parser = all_parsers midx = MultiIndex.from_tuples([("A", 1, 2), ("A", 1, 2), ("B", 1, 2)]) expected = DataFrame(np.random.randn(3, 3), index=midx, columns=["x", "y", "z"]) with tm.ensure_clean() as path: expected.to_csv(path) result = parser.read_csv(path, index_col=[0, 1, 2]) tm.assert_frame_equal(result, expected) def test_header_with_index_col(all_parsers): # GH 33476 parser = all_parsers data = """ I11,A,A I12,B,B I2,1,3 """ midx = MultiIndex.from_tuples([("A", "B"), ("A", "B.1")], names=["I11", "I12"]) idx = Index(["I2"]) expected = DataFrame([[1, 3]], index=idx, columns=midx) result = parser.read_csv(StringIO(data), index_col=0, header=[0, 1]) tm.assert_frame_equal(result, expected) col_idx = Index(["A", "A.1"]) idx = Index(["I12", "I2"], name="I11") expected = DataFrame([["B", "B"], ["1", "3"]], index=idx, columns=col_idx) result = parser.read_csv(StringIO(data), index_col="I11", header=0) tm.assert_frame_equal(result, expected) @pytest.mark.slow def test_index_col_large_csv(all_parsers): # https://github.com/pandas-dev/pandas/issues/37094 parser = all_parsers N = 1_000_001 df = DataFrame({"a": range(N), "b": np.random.randn(N)}) with tm.ensure_clean() as path: df.to_csv(path, index=False) result = parser.read_csv(path, index_col=[0]) tm.assert_frame_equal(result, df.set_index("a"))