BUG: Fixed getattr for frame with column sparse (#30759)

Closes #30758

Author: TomAugspurger

doc/source/whatsnew/v1.0.0.rst

@@ -1004,7 +1004,7 @@ Reshaping
 Sparse
 ^^^^^^
 - Bug in :class:`SparseDataFrame` arithmetic operations incorrectly casting inputs to float (:issue:`28107`)
--
+- Bug in ``DataFrame.sparse`` returning a ``Series`` when there was a column named ``sparse`` rather than the accessor (:issue:`30758`)
 -
 
 ExtensionArray

pandas/core/frame.py

@@ -402,7 +402,7 @@ def _constructor(self) -> Type["DataFrame"]:
 
     _constructor_sliced: Type[Series] = Series
     _deprecations: FrozenSet[str] = NDFrame._deprecations | frozenset([])
-    _accessors: Set[str] = set()
+    _accessors: Set[str] = {"sparse"}
 
     @property
     def _constructor_expanddim(self):

pandas/tests/arrays/sparse/test_accessor.py

@@ -116,3 +116,8 @@ def test_series_from_coo_incorrect_format_raises(self):
             TypeError, match="Expected coo_matrix. Got csr_matrix instead."
         ):
             pd.Series.sparse.from_coo(m)
+
+    def test_with_column_named_sparse(self):
+        # https://github.com/pandas-dev/pandas/issues/30758
+        df = pd.DataFrame({"sparse": pd.arrays.SparseArray([1, 2])})
+        assert isinstance(df.sparse, pd.core.arrays.sparse.accessor.SparseFrameAccessor)