REF: share _reduce (#36561)

Author: jbrockmendel

pandas/core/arrays/_mixins.py

@@ -227,3 +227,11 @@ def fillna(self: _T, value=None, method=None, limit=None) -> _T:
         else:
             new_values = self.copy()
         return new_values
+
+    def _reduce(self, name: str, skipna: bool = True, **kwargs):
+        meth = getattr(self, name, None)
+        if meth:
+            return meth(skipna=skipna, **kwargs)
+        else:
+            msg = f"'{type(self).__name__}' does not implement reduction '{name}'"
+            raise TypeError(msg)

pandas/core/arrays/categorical.py

@@ -1963,12 +1963,6 @@ def _reverse_indexer(self) -> Dict[Hashable, np.ndarray]:
     # ------------------------------------------------------------------
     # Reductions
 
-    def _reduce(self, name: str, skipna: bool = True, **kwargs):
-        func = getattr(self, name, None)
-        if func is None:
-            raise TypeError(f"Categorical cannot perform the operation {name}")
-        return func(skipna=skipna, **kwargs)
-
     @deprecate_kwarg(old_arg_name="numeric_only", new_arg_name="skipna")
     def min(self, skipna=True, **kwargs):
         """

pandas/core/arrays/datetimelike.py

@@ -1453,13 +1453,6 @@ def __isub__(self, other):
     # --------------------------------------------------------------
     # Reductions
 
-    def _reduce(self, name: str, skipna: bool = True, **kwargs):
-        op = getattr(self, name, None)
-        if op:
-            return op(skipna=skipna, **kwargs)
-        else:
-            return super()._reduce(name, skipna, **kwargs)
-
     def min(self, axis=None, skipna=True, *args, **kwargs):
         """
         Return the minimum value of the Array or minimum along

pandas/core/arrays/numpy_.py

@@ -272,14 +272,6 @@ def _values_for_factorize(self) -> Tuple[np.ndarray, int]:
     # ------------------------------------------------------------------------
     # Reductions
 
-    def _reduce(self, name, skipna=True, **kwargs):
-        meth = getattr(self, name, None)
-        if meth:
-            return meth(skipna=skipna, **kwargs)
-        else:
-            msg = f"'{type(self).__name__}' does not implement reduction '{name}'"
-            raise TypeError(msg)
-
     def any(self, axis=None, out=None, keepdims=False, skipna=True):
         nv.validate_any((), dict(out=out, keepdims=keepdims))
         return nanops.nanany(self._ndarray, axis=axis, skipna=skipna)

pandas/tests/arrays/categorical/test_operators.py

@@ -353,7 +353,7 @@ def test_numeric_like_ops(self):
         # min/max)
         s = df["value_group"]
         for op in ["kurt", "skew", "var", "std", "mean", "sum", "median"]:
-            msg = f"Categorical cannot perform the operation {op}"
+            msg = f"'Categorical' does not implement reduction '{op}'"
             with pytest.raises(TypeError, match=msg):
                 getattr(s, op)(numeric_only=False)
 
@@ -362,7 +362,7 @@ def test_numeric_like_ops(self):
         # numpy ops
         s = Series(Categorical([1, 2, 3, 4]))
         with pytest.raises(
-            TypeError, match="Categorical cannot perform the operation sum"
+            TypeError, match="'Categorical' does not implement reduction 'sum'"
         ):
             np.sum(s)
 

pandas/tests/arrays/test_datetimelike.py

@@ -205,7 +205,8 @@ def test_reduce_invalid(self):
         data = np.arange(10, dtype="i8") * 24 * 3600 * 10 ** 9
         arr = self.array_cls(data, freq="D")
 
-        with pytest.raises(TypeError, match="cannot perform"):
+        msg = f"'{type(arr).__name__}' does not implement reduction 'not a method'"
+        with pytest.raises(TypeError, match=msg):
             arr._reduce("not a method")
 
     @pytest.mark.parametrize("method", ["pad", "backfill"])

pandas/tests/reductions/test_reductions.py

@@ -351,6 +351,7 @@ def test_invalid_td64_reductions(self, opname):
             [
                 f"reduction operation '{opname}' not allowed for this dtype",
                 rf"cannot perform {opname} with type timedelta64\[ns\]",
+                f"'TimedeltaArray' does not implement reduction '{opname}'",
             ]
         )
 
@@ -695,6 +696,7 @@ def test_ops_consistency_on_empty(self, method):
                 [
                     "operation 'var' not allowed",
                     r"cannot perform var with type timedelta64\[ns\]",
+                    "'TimedeltaArray' does not implement reduction 'var'",
                 ]
             )
             with pytest.raises(TypeError, match=msg):