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BUG: DataFrame.loc not aligning dict when setting to a column #47361

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Merged
merged 6 commits into from
Jun 30, 2022
Merged

BUG: DataFrame.loc not aligning dict when setting to a column #47361

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88b5591
BUG: DataFrame.loc not aligning dict when setting to a column
phofl Jun 15, 2022
9dd728d
Add partial case
phofl Jun 16, 2022
3c614a9
Merge remote-tracking branch 'upstream/main' into 47216
phofl Jun 24, 2022
7403240
Merge remote-tracking branch 'upstream/main' into 47216
phofl Jun 27, 2022
d270851
Use is_dict_like
phofl Jun 28, 2022
6992ec4
Revert "Use is_dict_like"
phofl Jun 28, 2022
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.5.0.rst
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Expand Up @@ -821,6 +821,7 @@ Indexing
- Bug in :meth:`loc.__setitem__` treating ``range`` keys as positional instead of label-based (:issue:`45479`)
- Bug in :meth:`Series.__setitem__` when setting ``boolean`` dtype values containing ``NA`` incorrectly raising instead of casting to ``boolean`` dtype (:issue:`45462`)
- Bug in :meth:`Series.__setitem__` where setting :attr:`NA` into a numeric-dtpye :class:`Series` would incorrectly upcast to object-dtype rather than treating the value as ``np.nan`` (:issue:`44199`)
- Bug in :meth:`DataFrame.loc` when setting values to a column and right hand side is a dictionary (:issue:`47216`)
- Bug in :meth:`Series.__setitem__` with ``datetime64[ns]`` dtype, an all-``False`` boolean mask, and an incompatible value incorrectly casting to ``object`` instead of retaining ``datetime64[ns]`` dtype (:issue:`45967`)
- Bug in :meth:`Index.__getitem__` raising ``ValueError`` when indexer is from boolean dtype with ``NA`` (:issue:`45806`)
- Bug in :meth:`Series.mask` with ``inplace=True`` or setting values with a boolean mask with small integer dtypes incorrectly raising (:issue:`45750`)
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2 changes: 2 additions & 0 deletions pandas/core/frame.py
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Expand Up @@ -4699,6 +4699,8 @@ def _sanitize_column(self, value) -> ArrayLike:
# We should never get here with DataFrame value
if isinstance(value, Series):
return _reindex_for_setitem(value, self.index)
elif isinstance(value, dict):
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is_dict_like ?

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I aligned this with a codepath in indexing.py

        if (isinstance(value, ABCSeries) and name != "iloc") or isinstance(value, dict):
            from pandas import Series

            value = self._align_series(indexer, Series(value))

Not sure why we are calling for dict here, but should update in both places when we use is_dict_like here?

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is_dict_like returns True for Series, so it depends if the name != "iloc" is supposed to exclude a specific Series case?

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Ah good point. Yes iloc should not align, hence the condition

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Looks like we end up there with a DataFrame, which raises. Will investigate in follow up how this happens

return _reindex_for_setitem(Series(value), self.index)

if is_list_like(value):
com.require_length_match(value, self.index)
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12 changes: 12 additions & 0 deletions pandas/tests/frame/indexing/test_setitem.py
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Expand Up @@ -702,6 +702,18 @@ def test_setitem_npmatrix_2d(self):

tm.assert_frame_equal(df, expected)

@pytest.mark.parametrize("vals", [{}, {"d": "a"}])
def test_setitem_aligning_dict_with_index(self, vals):
# GH#47216
df = DataFrame({"a": [1, 2], "b": [3, 4], **vals})
df.loc[:, "a"] = {1: 100, 0: 200}
df.loc[:, "c"] = {0: 5, 1: 6}
df.loc[:, "e"] = {1: 5}
expected = DataFrame(
{"a": [200, 100], "b": [3, 4], **vals, "c": [5, 6], "e": [np.nan, 5]}
)
tm.assert_frame_equal(df, expected)


class TestSetitemTZAwareValues:
@pytest.fixture
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