Fix SparseDtype comparison

doc/source/whatsnew/v3.0.0.rst

@@ -280,6 +280,7 @@ Performance improvements
 
 Bug fixes
 ~~~~~~~~~
+- Fixed bug in :class:`SparseDtype` for equal comparison with na fill value. (:issue:`54770`)
 - Fixed bug in :meth:`DataFrame.join` inconsistently setting result index name (:issue:`55815`)
 - Fixed bug in :meth:`DataFrame.to_string` that raised ``StopIteration`` with nested DataFrames. (:issue:`16098`)
 - Fixed bug in :meth:`DataFrame.update` bool dtype being converted to object (:issue:`55509`)

pandas/core/dtypes/dtypes.py

@@ -1705,17 +1705,15 @@ def __eq__(self, other: object) -> bool:
 
         if isinstance(other, type(self)):
             subtype = self.subtype == other.subtype
-            if self._is_na_fill_value:
+            if self._is_na_fill_value or other._is_na_fill_value:
                 # this case is complicated by two things:
                 # SparseDtype(float, float(nan)) == SparseDtype(float, np.nan)
                 # SparseDtype(float, np.nan)     != SparseDtype(float, pd.NaT)
                 # i.e. we want to treat any floating-point NaN as equal, but
                 # not a floating-point NaN and a datetime NaT.
-                fill_value = (
-                    other._is_na_fill_value
-                    and isinstance(self.fill_value, type(other.fill_value))
-                    or isinstance(other.fill_value, type(self.fill_value))
-                )
+                fill_value = isinstance(
+                    self.fill_value, type(other.fill_value)
+                ) or isinstance(other.fill_value, type(self.fill_value))
             else:
                 with warnings.catch_warnings():
                     # Ignore spurious numpy warning

pandas/tests/arrays/sparse/test_dtype.py

@@ -68,6 +68,14 @@ def test_nans_equal():
     assert b == a
 
 
+def test_nans_not_equal():
+    # GH 54770
+    a = SparseDtype(float, 0)
+    b = SparseDtype(float, pd.NA)
+    assert a != b
+    assert b != a
+
+
 with warnings.catch_warnings():
     msg = "Allowing arbitrary scalar fill_value in SparseDtype is deprecated"
     warnings.filterwarnings("ignore", msg, category=FutureWarning)

pandas/tests/extension/test_sparse.py

@@ -240,10 +240,6 @@ def test_fillna_limit_backfill(self, data_missing):
             super().test_fillna_limit_backfill(data_missing)
 
     def test_fillna_no_op_returns_copy(self, data, request):
-        if np.isnan(data.fill_value):
-            request.applymarker(
-                pytest.mark.xfail(reason="returns array with different fill value")
-            )
         super().test_fillna_no_op_returns_copy(data)
 
     @pytest.mark.xfail(reason="Unsupported")
@@ -400,6 +396,8 @@ def test_arith_frame_with_scalar(self, data, all_arithmetic_operators, request):
             "rmul",
             "floordiv",
             "rfloordiv",
+            "truediv",
+            "rtruediv",
             "pow",
             "mod",
             "rmod",