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BUG: Fix return type of loc/iloc #61054

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BUG: Fix return type of loc/iloc #61054

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5003eaa
Fix loc dtype
sanggon6107 Mar 4, 2025
d4a031b
Modify test_loc_setitem_frame_mixed_labels accordingly
sanggon6107 Mar 4, 2025
2536652
Add test for the linked issue
sanggon6107 Mar 4, 2025
c5a5de1
Fix test_loc_dtype
sanggon6107 Mar 4, 2025
1f529ce
Fix dtype inference
sanggon6107 Mar 6, 2025
ec9fd4f
Merge branch 'main' of https://github.com/sanggon6107/pandas into fix…
sanggon6107 Mar 13, 2025
d2e29c0
Reverse tuple to avoid unintended dtype inference
sanggon6107 Mar 13, 2025
74eb356
Reverse axis order
sanggon6107 Mar 17, 2025
8677f0d
Merge branch 'main' into fix-loc-dtype
sanggon6107 Mar 31, 2025
6388d93
Reverse indexing order
sanggon6107 Apr 2, 2025
319d717
Merge branch 'main' into fix-loc-dtype
sanggon6107 Apr 17, 2025
3596f76
Explicitly assign the expected result
sanggon6107 Apr 17, 2025
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11 changes: 10 additions & 1 deletion pandas/core/indexing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1094,7 +1094,16 @@ def _getitem_lowerdim(self, tup: tuple):
if com.is_null_slice(new_key):
return section
# This is an elided recursive call to iloc/loc
return getattr(section, self.name)[new_key]
out = getattr(section, self.name)[new_key]
# Re-interpret dtype of out.values for loc/iloc[int, list/slice].
# GH60600
if (
i == 0
and isinstance(key, int)
and isinstance(new_key, (list, slice))
):
out = out.infer_objects()
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This will infer non-object dtype even on data that is object-dtype, no? I do not think this is the right change.

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Thanks @rhshadrach !
I've also confirmed what you've mentioned.

>>>import pandas as pd
>>> df = pd.DataFrame({1: [11, 22], 2: [33, 44], "a": [55, 66]}, dtype=object)

>>>df.loc[0, [1, 2]]
1	11
2	33
Name: 0, dtype: int64

>>>df[[1, 2]].loc[0]
1	11
2	33
Name: 0, dtype: object

I'll do some further investigation to fix this.

return out

raise IndexingError("not applicable")

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10 changes: 9 additions & 1 deletion pandas/tests/indexing/test_loc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,14 @@ def test_not_change_nan_loc(series, new_series, expected_ser):
tm.assert_frame_equal(df.notna(), ~expected)


def test_loc_dtype():
# GH 60600
df = DataFrame([["a", 1.0, 2.0], ["b", 3.0, 4.0]])
result = df.loc[0, [1, 2]]
expected = df[[1, 2]].loc[0]
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Can you provide expected explicitly here: expected = DataFrame(...)

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Made the code change. Thanks for the suggestion!

tm.assert_series_equal(result, expected)


class TestLoc:
def test_none_values_on_string_columns(self, using_infer_string):
# Issue #32218
Expand Down Expand Up @@ -807,7 +815,7 @@ def test_loc_setitem_frame_mixed_labels(self):

result = df.loc[0, [1, 2]]
expected = Series(
[1, 3], index=Index([1, 2], dtype=object), dtype=object, name=0
[1, 3], index=Index([1, 2], dtype=object), dtype="int64", name=0
)
tm.assert_series_equal(result, expected)

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