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Fix slicer assignment bug #28131

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Merged
merged 5 commits into from
Aug 28, 2019
Merged

Fix slicer assignment bug #28131

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8a1b004
BUG: adds test for GH26939
RoeiRaz Aug 25, 2019
a41b964
BUG: fixes GH26939
RoeiRaz Aug 25, 2019
9a93e8e
Update indexers.py
RoeiRaz Aug 25, 2019
467d9fe
Update test_loc.py
RoeiRaz Aug 27, 2019
94bf51e
Update v1.0.0.rst
RoeiRaz Aug 28, 2019
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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v1.0.0.rst
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Expand Up @@ -140,7 +140,7 @@ Interval
Indexing
^^^^^^^^

-
- Bug in assignment using a reverse slicer (:issue:`26939`)
-

Missing
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1 change: 1 addition & 0 deletions pandas/core/indexers.py
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Expand Up @@ -226,6 +226,7 @@ def length_of_indexer(indexer, target=None) -> int:
if step is None:
step = 1
elif step < 0:
start, stop = stop + 1, start + 1
step = -step
return (stop - start + step - 1) // step
elif isinstance(indexer, (ABCSeries, ABCIndexClass, np.ndarray, list)):
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10 changes: 10 additions & 0 deletions pandas/tests/indexing/test_loc.py
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Expand Up @@ -1070,6 +1070,16 @@ def test_series_indexing_zerodim_np_array(self):
result = s.loc[np.array(0)]
assert result == 1

def test_loc_reverse_assignment(self):
# GH26939
data = [1, 2, 3, 4, 5, 6] + [None] * 4
expected = Series(data, index=range(2010, 2020))

result = pd.Series(index=range(2010, 2020))
result.loc[2015:2010:-1] = [6, 5, 4, 3, 2, 1]

tm.assert_series_equal(result, expected)


def test_series_loc_getitem_label_list_missing_values():
# gh-11428
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