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BUG: Scalar assignment to empty dataframe with loc. Closes GH41891 #41921

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BUG: Scalar assignment to empty dataframe with loc. Closes GH41891 #41921

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9 changes: 5 additions & 4 deletions pandas/core/indexing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1646,10 +1646,11 @@ def _setitem_with_indexer(self, indexer, value, name="iloc"):
if self.ndim > 1 and i == info_axis:

# add the new item, and set the value
# must have all defined axes if we have a scalar
# or a list-like on the non-info axes if we have a
# list-like
if not len(self.obj):
# If we have a scalar as values, must have all defined
# axes or be an empty slice.
# If we have a list-like as value, must have a
# list-like on the non-info axes
if not len(self.obj) and not com.is_null_slice(indexer[0]):
if not is_list_like_indexer(value):
raise ValueError(
"cannot set a frame with no "
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6 changes: 5 additions & 1 deletion pandas/tests/indexing/test_partial.py
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Original file line number Diff line number Diff line change
Expand Up @@ -384,7 +384,11 @@ def test_partial_set_empty_frame(self):

msg = "cannot set a frame with no defined index and a scalar"
with pytest.raises(ValueError, match=msg):
df.loc[:, 1] = 1
df.loc[3:4, 1] = 1

df.loc[:, 1] = 1
assert df.columns.to_list() == [1]
assert len(df) == 0

def test_partial_set_empty_frame2(self):
# these work as they don't really change
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