Raise if None is passed for skipna

doc/source/whatsnew/v1.4.0.rst

@@ -399,6 +399,7 @@ Other API changes
 ^^^^^^^^^^^^^^^^^
 - :meth:`Index.get_indexer_for` no longer accepts keyword arguments (other than 'target'); in the past these would be silently ignored if the index was not unique (:issue:`42310`)
 - Change in the position of the ``min_rows`` argument in :meth:`DataFrame.to_string` due to change in the docstring (:issue:`44304`)
+- Reduction operations for :class:`DataFrame` or :class:`Series` now raising a ``ValueError`` when ``None`` is passed for ``skipna`` (:issue:`44178`)
 -
 
 .. ---------------------------------------------------------------------------

pandas/core/generic.py

@@ -10303,6 +10303,7 @@ def _logical_func(
         self, name: str, func, axis=0, bool_only=None, skipna=True, level=None, **kwargs
     ):
         nv.validate_logical_func((), kwargs, fname=name)
+        validate_bool_kwarg(skipna, "skipna", none_allowed=False)
         if level is not None:
             warnings.warn(
                 "Using the level keyword in DataFrame and Series aggregations is "
@@ -10397,6 +10398,7 @@ def _stat_function_ddof(
         **kwargs,
     ):
         nv.validate_stat_ddof_func((), kwargs, fname=name)
+        validate_bool_kwarg(skipna, "skipna", none_allowed=False)
         if axis is None:
             axis = self._stat_axis_number
         if level is not None:
@@ -10450,6 +10452,9 @@ def _stat_function(
             nv.validate_median((), kwargs)
         else:
             nv.validate_stat_func((), kwargs, fname=name)
+
+        validate_bool_kwarg(skipna, "skipna", none_allowed=False)
+
         if axis is None:
             axis = self._stat_axis_number
         if level is not None:
@@ -10517,6 +10522,9 @@ def _min_count_stat_function(
             nv.validate_prod((), kwargs)
         else:
             nv.validate_stat_func((), kwargs, fname=name)
+
+        validate_bool_kwarg(skipna, "skipna", none_allowed=False)
+
         if axis is None:
             axis = self._stat_axis_number
         if level is not None:
@@ -10669,7 +10677,7 @@ def all(self, axis=0, bool_only=None, skipna=True, level=None, **kwargs):
             see_also="",
             examples="",
         )
-        def mad(self, axis=None, skipna=None, level=None):
+        def mad(self, axis=None, skipna=True, level=None):
             return NDFrame.mad(self, axis, skipna, level)
 
         setattr(cls, "mad", mad)

pandas/tests/apply/test_str.py

@@ -26,7 +26,7 @@
         pytest.param([1], {}, id="axis_from_args"),
         pytest.param([], {"axis": 1}, id="axis_from_kwds"),
         pytest.param([], {"numeric_only": True}, id="optional_kwds"),
-        pytest.param([1, None], {"numeric_only": True}, id="args_and_kwds"),
+        pytest.param([1, True], {"numeric_only": True}, id="args_and_kwds"),
     ],
 )
 @pytest.mark.parametrize("how", ["agg", "apply"])

pandas/tests/frame/conftest.py

@@ -259,3 +259,26 @@ def frame_of_index_cols():
         }
     )
     return df
+
+
+@pytest.fixture(
+    params=[
+        "any",
+        "all",
+        "count",
+        "sum",
+        "prod",
+        "max",
+        "min",
+        "mean",
+        "median",
+        "skew",
+        "kurt",
+        "sem",
+        "var",
+        "std",
+        "mad",
+    ]
+)
+def reduction_functions(request):
+    return request.param

pandas/tests/frame/test_reductions.py

@@ -1478,33 +1478,23 @@ def test_frame_any_with_timedelta(self):
         expected = Series(data=[False, True])
         tm.assert_series_equal(result, expected)
 
-    @pytest.mark.parametrize(
-        "func",
-        [
-            "any",
-            "all",
-            "count",
-            "sum",
-            "prod",
-            "max",
-            "min",
-            "mean",
-            "median",
-            "skew",
-            "kurt",
-            "sem",
-            "var",
-            "std",
-            "mad",
-        ],
-    )
-    def test_reductions_deprecation_level_argument(self, frame_or_series, func):
+    def test_reductions_deprecation_level_argument(
+        self, frame_or_series, reduction_functions
+    ):
         # GH#39983
         obj = frame_or_series(
             [1, 2, 3], index=MultiIndex.from_arrays([[1, 2, 3], [4, 5, 6]])
         )
         with tm.assert_produces_warning(FutureWarning, match="level"):
-            getattr(obj, func)(level=0)
+            getattr(obj, reduction_functions)(level=0)
+
+    def test_reductions_skipna_none_raises(self, frame_or_series, reduction_functions):
+        if reduction_functions in ["count", "mad"]:
+            pytest.skip("Count does not accept skipna. Mad needs a depreaction cycle.")
+        obj = frame_or_series([1, 2, 3])
+        msg = 'For argument "skipna" expected type bool, received type NoneType.'
+        with pytest.raises(ValueError, match=msg):
+            getattr(obj, reduction_functions)(skipna=None)
 
 
 class TestNuisanceColumns: