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Fixed #38419 - BUG: set_index screws up the dtypes on empty DataFrames #38430

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Merged
jreback merged 1 commit into from
Dec 13, 2020
Merged

Fixed #38419 - BUG: set_index screws up the dtypes on empty DataFrames #38430

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11 changes: 11 additions & 0 deletions pandas/tests/frame/methods/test_set_index.py
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,17 @@ def test_set_index_empty_column(self):
expected.index = MultiIndex.from_arrays([df["a"], df["x"]], names=["a", "x"])
tm.assert_frame_equal(result, expected)

def test_set_index_empty_dataframe(self):
# GH#38419
df1 = DataFrame(
{"a": Series(dtype="datetime64[ns]"), "b": Series(dtype="int64"), "c": []}
)

df2 = df1.set_index(["a", "b"])
result = df2.index.to_frame().dtypes
expected = df1[["a", "b"]].dtypes
tm.assert_series_equal(result, expected)

def test_set_index_multiindexcolumns(self):
columns = MultiIndex.from_tuples([("foo", 1), ("foo", 2), ("bar", 1)])
df = DataFrame(np.random.randn(3, 3), columns=columns)
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