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TST: add test on checking objects to concatenate #40822

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Merged
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Apr 8, 2021
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TST: add test on checking objects to concatenate #40822

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TST: add test on checking objects to concatenate
ivanovmg Apr 7, 2021
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TST: move test to similar ones
ivanovmg Apr 7, 2021
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5 changes: 5 additions & 0 deletions pandas/tests/reshape/concat/test_concat.py
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Original file line number Diff line number Diff line change
Expand Up @@ -599,3 +599,8 @@ def test_concat_repeated_keys(keys, integrity):
tuples = list(zip(keys, ["a", "b", "c"]))
expected = Series([1, 2, 3], index=MultiIndex.from_tuples(tuples))
tm.assert_series_equal(result, expected)


def test_concat_no_items_raises():
with pytest.raises(ValueError, match="No objects to concatenate"):
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is there a reference somewhere of discussion on why this should raise rather than return an empty Series/DataFrame?

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Came up in #40820

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we don't have any other tests for this?

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@jreback jreback Apr 7, 2021 •
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def test_concat_exclude_none(self):
        df = DataFrame(np.random.randn(10, 4))

        pieces = [df[:5], None, None, df[5:]]
        result = concat(pieces)
        tm.assert_frame_equal(result, df)
        with pytest.raises(ValueError, match="All objects passed were None"):
            concat([None, None])

put near this one

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we don't have any other tests for this?

By grepping I did not find that concat is anywhere invoked on an empty list, besides this new test.

$ grep -oPrn 'concat\(\[\]\)' pandas/tests
pandas/tests/reshape/concat/test_concat.py:606:concat([])

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can you put it next to the test as i indicated above

concat([])