SparseSeries unstack

Author: TomAugspurger

doc/source/whatsnew/v0.24.0.rst

@@ -1103,6 +1103,7 @@ Other API Changes
 - The order of the arguments of :func:`DataFrame.to_html` and :func:`DataFrame.to_string` is rearranged to be consistent with each other. (:issue:`23614`)
 - :meth:`CategoricalIndex.reindex` now raises a ``ValueError`` if the target index is non-unique and not equal to the current index. It previously only raised if the target index was not of a categorical dtype (:issue:`23963`).
 - :func:`Series.to_list` and :func:`Index.to_list` are now aliases of ``Series.tolist`` respectively ``Index.tolist`` (:issue:`8826`)
+- The result of ``SparseSeries.unstack`` is now a :class:`DataFrame` with sparse values, rather than a :class:`SparseDataFrame` (issue:`24372`).
 
 .. _whatsnew_0240.deprecations:
 

pandas/tests/sparse/test_reshape.py

@@ -35,4 +35,8 @@ def test_sparse_frame_unstack(sparse_df):
 
 def test_sparse_series_unstack(sparse_df, multi_index3):
     frame = pd.SparseSeries(np.ones(3), index=multi_index3).unstack()
-    tm.assert_sp_frame_equal(frame, sparse_df)
+
+    arr = np.array([1, np.nan, np.nan])
+    arrays = {i: pd.SparseArray(np.roll(arr, i)) for i in range(3)}
+    expected = pd.DataFrame(arrays)
+    tm.assert_frame_equal(frame, expected)