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Added test case to lock in behaviour #48541

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Merged
mroeschke merged 5 commits into from
Sep 15, 2022
Merged

Added test case to lock in behaviour #48541

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0fed6c7
Added test case to lock in behaviour
Sep 14, 2022
c7920bc
Update whatsnew
Sep 14, 2022
fd79476
Addressed code review comments
Sep 14, 2022
711906b
Fixed style issue
Sep 15, 2022
4675802
Improved whatsnew entry as per suggestion
Sep 15, 2022
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v1.6.0.rst
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Expand Up @@ -212,6 +212,7 @@ Sparse
ExtensionArray
^^^^^^^^^^^^^^
- Bug in :meth:`Series.mean` overflowing unnecessarily with nullable integers (:issue:`48378`)
- Bug when concatenating an empty DataFrame with an ExtensionDtype to another DataFrame with the same ExtensionDtype, the resulting dtype turned into object (:issue:`48510`)
-

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8 changes: 8 additions & 0 deletions pandas/tests/reshape/concat/test_empty.py
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Expand Up @@ -284,3 +284,11 @@ def test_concat_empty_dataframe_different_dtypes(self):
result = concat([df1[:0], df2[:0]])
assert result["a"].dtype == np.int64
assert result["b"].dtype == np.object_

def test_concat_to_empty_ea(self):
"""48510 `concat` to an empty EA should maintain type EA dtype."""
df_empty = DataFrame({"a": pd.array([], dtype=pd.Int64Dtype())})
df_new = DataFrame({"a": pd.array([1, 2, 3], dtype=pd.Int64Dtype())})
expected = df_new.copy()
result = concat([df_empty, df_new])
tm.assert_frame_equal(result, expected)