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BUG: Fix 57735 #59335

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Merged
merged 7 commits into from
Jul 29, 2024
Merged

BUG: Fix 57735 #59335

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e2b809a
Revert "CLN: Remove special cases in indexing ops (#52063)"
matiaslindgren Jul 27, 2024
cc06fb0
remove old comments, add test
matiaslindgren Jul 27, 2024
efba5a5
use better test name
matiaslindgren Jul 27, 2024
7f937d8
Update pandas/tests/indexing/test_loc.py
matiaslindgren Jul 29, 2024
20e21f0
check for empty index first
matiaslindgren Jul 29, 2024
78ccf15
assert assign to empty does not change frame
matiaslindgren Jul 29, 2024
c9e78a7
format
matiaslindgren Jul 29, 2024
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16 changes: 11 additions & 5 deletions pandas/core/indexing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -810,8 +810,11 @@ def _maybe_mask_setitem_value(self, indexer, value):

if is_scalar_indexer(icols, self.ndim - 1) and ndim == 1:
# e.g. test_loc_setitem_boolean_mask_allfalse
# test_loc_setitem_ndframe_values_alignment
value = self.obj.iloc._align_series(indexer, value)
if len(newkey) == 0:
value = value.iloc[:0]
else:
# test_loc_setitem_ndframe_values_alignment
value = self.obj.iloc._align_series(indexer, value)
indexer = (newkey, icols)

elif (
Expand All @@ -827,8 +830,11 @@ def _maybe_mask_setitem_value(self, indexer, value):
indexer = (newkey, icols)

elif ndim == 2 and value.shape[1] == 1:
# test_loc_setitem_ndframe_values_alignment
value = self.obj.iloc._align_frame(indexer, value)
if len(newkey) == 0:
value = value.iloc[:0]
else:
# test_loc_setitem_ndframe_values_alignment
value = self.obj.iloc._align_frame(indexer, value)
indexer = (newkey, icols)
elif com.is_bool_indexer(indexer):
indexer = indexer.nonzero()[0]
Expand Down Expand Up @@ -2389,7 +2395,7 @@ def ravel(i):
new_ix = Index([new_ix])
else:
new_ix = Index(new_ix)
if ser.index.equals(new_ix):
if not len(new_ix) or ser.index.equals(new_ix):
if using_cow:
return ser
return ser._values.copy()
Expand Down
7 changes: 7 additions & 0 deletions pandas/tests/indexing/test_loc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3272,3 +3272,10 @@ def test_loc_index_alignment_for_series(self):
df.loc[:, "a"] = other
expected = DataFrame({"a": [999, 200], "b": [3, 4]})
tm.assert_frame_equal(expected, df)

def test_loc_reindexing_of_empty_index(self):
# GH 57735
df = DataFrame(index=[1, 1, 2, 2], data=["1", "1", "2", "2"])
df.loc[Series([False] * 4, index=df.index, name=0), 0] = df[0]
expected = DataFrame(index=[1, 1, 2, 2], data=["1", "1", "2", "2"])
tm.assert_frame_equal(df, expected)
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