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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
16478e5
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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Original file line number Diff line number Diff line change
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("pivot() missing 1 required argument: 'columns'")
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This should be a TypeError no? I think @simonjayhawkins had that original comment

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sorry, i thought ValueError is more appropriate here for this case.

I changed to TypeError as suggested by @simonjayhawkins ! thanks both!

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This should be a TypeError no? I think @simonjayhawkins had that original comment

I think it should be TypeError, however, I would regard a change from ValueError to TypeError as a breaking change. Not sure what others think.

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nvm. The exception in the issue is a KeyError, so either is a change.

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get it! thanks!


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 = 'pivot["(][")] missing 1 required argument: ["\']columns["\']'
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if you use re.escape, this may be more readable.

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thanks for your quick response, i tried re.escape, but it seemed to work in an opposite way. @simonjayhawkins could you pls enlighten me a bit?

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Suggested change
msg = 'pivot["(][")] missing 1 required argument: ["\']columns["\']'
msg = re.escape("pivot() missing 1 required argument: 'columns'")

also need to import re

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@charlesdong1991 charlesdong1991 Jan 13, 2020 •
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ahh, i see!!! thanks! @simonjayhawkins

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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