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BUG: correct wrong error message in df.pivot when columns=None #30925

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Merged
merged 13 commits into from
Jan 18, 2020
Merged

BUG: correct wrong error message in df.pivot when columns=None #30925

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7e461a1
remove \n from docstring
charlesdong1991 Dec 3, 2018
1314059
fix conflicts
charlesdong1991 Jan 19, 2019
8bcb313
Merge remote-tracking branch 'upstream/master'
charlesdong1991 Jul 30, 2019
776e9ae
Merge remote-tracking branch 'upstream/master' into fix_issue_21425
charlesdong1991 Jan 11, 2020
4895497
correct error message
charlesdong1991 Jan 11, 2020
f4380cd
code change on Simon review
charlesdong1991 Jan 13, 2020
e60ffee
update test
charlesdong1991 Jan 13, 2020
61ac061
Merge remote-tracking branch 'upstream/master' into fix_issue_21425
charlesdong1991 Jan 13, 2020
d03452f
add whatsnew
charlesdong1991 Jan 13, 2020
abce670
change to typeerror and resolve conflict and merge master
charlesdong1991 Jan 15, 2020
28d3d41
fix conflict
charlesdong1991 Jan 18, 2020
c650a05
better whatsnew
charlesdong1991 Jan 18, 2020
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remove re
charlesdong1991 Jan 18, 2020
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3 changes: 3 additions & 0 deletions pandas/core/reshape/pivot.py
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Expand Up @@ -427,6 +427,9 @@ def _convert_by(by):
@Substitution("\ndata : DataFrame")
@Appender(_shared_docs["pivot"], indents=1)
def pivot(data: "DataFrame", index=None, columns=None, values=None) -> "DataFrame":
if columns is None:
raise ValueError("`columns` is not optional.")
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since I don't think we can change the function signature, then to be semi consistent with standard error messages, then maybe TypeError: pivot() missing 1 required argument: 'columns'

(or an enhancement to the code so that columns is the remaining columns not in index and values arguments, and then raise a message that at least one of columns and values must be specified


if values is None:
cols = [columns] if index is None else [index, columns]
append = index is None
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9 changes: 9 additions & 0 deletions pandas/tests/reshape/test_pivot.py
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Expand Up @@ -781,6 +781,15 @@ def test_pivot_with_list_like_values_nans(self, values, method):
expected = DataFrame(data=data, index=index, columns=columns, dtype="object")
tm.assert_frame_equal(result, expected)

def test_pivot_columns_none_raise_error(self):
# GH 30924
df = pd.DataFrame(
{"col1": ["a", "b", "c"], "col2": [1, 2, 3], "col3": [1, 2, 3]}
)
msg = "`columns` is not optional."
with pytest.raises(ValueError, match=msg):
df.pivot(index="col1", values="col3")

@pytest.mark.xfail(
reason="MultiIndexed unstack with tuple names fails with KeyError GH#19966"
)
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