Deprecate skipna=None for mad

doc/source/whatsnew/v1.4.0.rst

@@ -464,6 +464,7 @@ Other Deprecations
 - Deprecated casting behavior when passing an item with mismatched-timezone to :meth:`DatetimeIndex.insert`, :meth:`DatetimeIndex.putmask`, :meth:`DatetimeIndex.where` :meth:`DatetimeIndex.fillna`, :meth:`Series.mask`, :meth:`Series.where`, :meth:`Series.fillna`, :meth:`Series.shift`, :meth:`Series.replace`, :meth:`Series.reindex` (and :class:`DataFrame` column analogues). In the past this has cast to object dtype. In a future version, these will cast the passed item to the index or series's timezone (:issue:`37605`)
 - Deprecated the 'errors' keyword argument in :meth:`Series.where`, :meth:`DataFrame.where`, :meth:`Series.mask`, and meth:`DataFrame.mask`; in a future version the argument will be removed (:issue:`44294`)
 - Deprecated :meth:`PeriodIndex.astype` to ``datetime64[ns]`` or ``DatetimeTZDtype``, use ``obj.to_timestamp(how).tz_localize(dtype.tz)`` instead (:issue:`44398`)
+- Deprecated passing ``skipna=None`` for :meth:`DataFrame.mad` and :meth:`Series.mad`, pass ``skipna=True`` instead (:issue:`44580`)
 - Deprecated :meth:`DateOffset.apply`, use ``offset + other`` instead (:issue:`44522`)
 -
 

pandas/core/generic.py

@@ -10579,15 +10579,15 @@ def prod(
 
     product = prod
 
-    def mad(self, axis=None, skipna=None, level=None):
+    def mad(self, axis=None, skipna=True, level=None):
         """
         {desc}
 
         Parameters
         ----------
         axis : {axis_descr}
             Axis for the function to be applied on.
-        skipna : bool, default None
+        skipna : bool, default True
             Exclude NA/null values when computing the result.
         level : int or level name, default None
             If the axis is a MultiIndex (hierarchical), count along a
@@ -10599,7 +10599,14 @@ def mad(self, axis=None, skipna=None, level=None):
         {see_also}\
         {examples}
         """
-        if skipna is None:
+        if not is_bool(skipna):
+            warnings.warn(
+                "Passing None for skipna is deprecated and will raise in a future"
+                "version. Pass True instead. Only boolean values will be allowed "
+                "in the future.",
+                FutureWarning,
+                stacklevel=find_stack_level(),
+            )
             skipna = True
         if axis is None:
             axis = self._stat_axis_number
@@ -10669,7 +10676,7 @@ 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/frame/test_reductions.py

@@ -1478,6 +1478,12 @@ def test_frame_any_with_timedelta(self):
         expected = Series(data=[False, True])
         tm.assert_series_equal(result, expected)
 
+    def test_reductions_deprecation_skipna_none(self, frame_or_series):
+        # GH#44580
+        obj = frame_or_series([1, 2, 3])
+        with tm.assert_produces_warning(FutureWarning, match="skipna"):
+            obj.mad(skipna=None)
+
     @pytest.mark.parametrize(
         "func",
         [