DEPR: Deprecate Series/Dataframe.to_dense/to_sparse

doc/source/whatsnew/v0.25.0.rst

@@ -503,6 +503,7 @@ Other Deprecations
 - The :meth:`Series.ftype`, :meth:`Series.ftypes` and :meth:`DataFrame.ftypes` methods are deprecated and will be removed in a future version.
   Instead, use :meth:`Series.dtype` and :meth:`DataFrame.dtypes` (:issue:`26705`).
 - :meth:`Timedelta.resolution` is deprecated and replaced with :meth:`Timedelta.resolution_string`.  In a future version, :meth:`Timedelta.resolution` will be changed to behave like the standard library :attr:`timedelta.resolution` (:issue:`21344`)
+- :meth:`Series.to_sparse`, :meth:`DataFrame.to_sparse`, :meth:`Series.to_dense` and :meth:`DataFrame.to_dense` are deprecated and will be removed in a future version. (:issue:`26557`).
 
 .. _whatsnew_0250.prior_deprecations:
 

pandas/core/sparse/frame.py

@@ -282,21 +282,6 @@ def _unpickle_sparse_frame_compat(self, state):
 
     @Appender(SparseFrameAccessor.to_dense.__doc__)
     def to_dense(self):
-        """
-        .. deprecated:: 0.25.0
-            Use Dataframe.sparse.to_dense() instead
-        """
-
-        warning_message = """\
-SparseDataFrame.to_dense is deprecated and will be removed in a future version
-
-            Use Dataframe.sparse.to_dense() instead
-
-            >>> df = pd.DataFrame({"A": pd.SparseArray([0, 1, 0])})
-            >>> df.sparse.to_dense()
-            """
-        warnings.warn(warning_message, FutureWarning, stacklevel=2)
-
         return SparseFrameAccessor(self).to_dense()
 
     def _apply_columns(self, func):

pandas/core/sparse/series.py

@@ -432,16 +432,10 @@ def to_dense(self):
         """
         Convert SparseSeries to a Series.
 
-        .. deprecated:: 0.25.0
-
         Returns
         -------
         s : Series
         """
-        warnings.warn("SparseSeries.to_dense is deprecated "
-                      "and will be removed in a future version",
-                      FutureWarning, stacklevel=2)
-
         return Series(self.values.to_dense(), index=self.index,
                       name=self.name)
 

pandas/tests/sparse/frame/test_frame.py

@@ -350,6 +350,18 @@ def test_dense_to_sparse(self):
         assert sdf.default_fill_value == 0
         tm.assert_frame_equal(sdf.to_dense(), df)
 
+    def test_deprecated_dense_to_sparse(self):
+        # GH 26557
+        # Deprecated 0.25.0
+
+        df = pd.DataFrame({"A": [1, np.nan, 3]})
+        sparse_df = pd.SparseDataFrame({"A": [1, np.nan, 3]})
+
+        with tm.assert_produces_warning(FutureWarning,
+                                        check_stacklevel=False):
+            result = df.to_sparse()
+        tm.assert_frame_equal(result, sparse_df)
+
     def test_density(self):
         df = SparseSeries([nan, nan, nan, 0, 1, 2, 3, 4, 5, 6])
         assert df.density == 0.7
@@ -1419,16 +1431,3 @@ def test_dropna(self, inplace, how):
         if inplace:
             result_df = input_df
         tm.assert_sp_frame_equal(expected, result_df)
-
-
-def test_deprecated_to_dense():
-    # GH 26557
-    # Deprecated 0.25.0
-
-    df = pd.DataFrame({"A": [1, np.nan, 3]})
-
-    with tm.assert_produces_warning(FutureWarning,
-                                    check_stacklevel=False):
-        sparse_df = pd.SparseDataFrame({"A": [1, np.nan, 3]})
-        result = sparse_df.to_dense()
-    tm.assert_frame_equal(result, df)

pandas/tests/sparse/series/test_series.py

@@ -1551,6 +1551,20 @@ def test_to_sparse():
     tm.assert_sp_array_equal(result.values, arr, check_kind=False)
 
 
+@pytest.mark.filterwarnings("ignore:Sparse:FutureWarning")
+def test_deprecated_to_sparse():
+    # GH 26557
+    # Deprecated 0.25.0
+
+    ser = Series([1, np.nan, 3])
+    sparse_ser = pd.SparseSeries([1, np.nan, 3])
+
+    with tm.assert_produces_warning(FutureWarning,
+                                    check_stacklevel=False):
+        result = ser.to_sparse()
+    tm.assert_series_equal(result, sparse_ser)
+
+
 @pytest.mark.filterwarnings("ignore:Sparse:FutureWarning")
 def test_constructor_mismatched_raises():
     msg = "Length of passed values is 2, index implies 3"
@@ -1563,17 +1577,3 @@ def test_block_deprecated():
     s = SparseSeries([1])
     with tm.assert_produces_warning(FutureWarning):
         s.block
-
-
-@pytest.mark.filterwarnings("ignore:Sparse:FutureWarning")
-def test_deprecate_to_dense():
-    # GH 26557
-    # Deprecated 0.25.0
-
-    ser = pd.Series([1, 2, 3])
-    sparse_ser = pd.SparseSeries([1, 2, 3])
-
-    # Deprecated 0.25.0
-    with tm.assert_produces_warning(FutureWarning):
-        result = sparse_ser.to_dense()
-        tm.assert_series_equal(result, ser)