CLN: Change Categorical.map(na_action=) default to None

doc/source/whatsnew/v3.0.0.rst

@@ -243,6 +243,7 @@ Removal of prior version deprecations/changes
 - Removed the "closed" and "unit" keywords in :meth:`TimedeltaIndex.__new__` (:issue:`52628`, :issue:`55499`)
 - All arguments in :meth:`Index.sort_values` are now keyword only (:issue:`56493`)
 - All arguments in :meth:`Series.to_dict` are now keyword only (:issue:`56493`)
+- Changed the default value of ``na_action`` in :meth:`Categorical.map` to ``None`` (:issue:`51645`)
 - Changed the default value of ``observed`` in :meth:`DataFrame.groupby` and :meth:`Series.groupby` to ``True`` (:issue:`51811`)
 - Enforce deprecation in :func:`testing.assert_series_equal` and :func:`testing.assert_frame_equal` with object dtype and mismatched null-like values, which are now considered not-equal (:issue:`18463`)
 - Enforced deprecation ``all`` and ``any`` reductions with ``datetime64``, :class:`DatetimeTZDtype`, and :class:`PeriodDtype` dtypes (:issue:`58029`)

pandas/core/arrays/arrow/array.py

@@ -1425,7 +1425,7 @@ def to_numpy(
             result[~mask] = data[~mask]._pa_array.to_numpy()
         return result
 
-    def map(self, mapper, na_action=None):
+    def map(self, mapper, na_action: Literal["ignore"] | None = None):
         if is_numeric_dtype(self.dtype):
             return map_array(self.to_numpy(), mapper, na_action=na_action)
         else:

pandas/core/arrays/base.py

@@ -2270,7 +2270,7 @@ def __array_ufunc__(self, ufunc: np.ufunc, method: str, *inputs, **kwargs):
 
         return arraylike.default_array_ufunc(self, ufunc, method, *inputs, **kwargs)
 
-    def map(self, mapper, na_action=None):
+    def map(self, mapper, na_action: Literal["ignore"] | None = None):
         """
         Map values using an input mapping or function.
 

pandas/core/arrays/categorical.py

@@ -1483,7 +1483,7 @@ def remove_unused_categories(self) -> Self:
     def map(
         self,
         mapper,
-        na_action: Literal["ignore"] | None | lib.NoDefault = lib.no_default,
+        na_action: Literal["ignore"] | None = None,
     ):
         """
         Map categories using an input mapping or function.
@@ -1501,15 +1501,10 @@ def map(
         ----------
         mapper : function, dict, or Series
             Mapping correspondence.
-        na_action : {None, 'ignore'}, default 'ignore'
+        na_action : {None, 'ignore'}, default None
             If 'ignore', propagate NaN values, without passing them to the
             mapping correspondence.
 
-            .. deprecated:: 2.1.0
-
-               The default value of 'ignore' has been deprecated and will be changed to
-               None in the future.
-
         Returns
         -------
         pandas.Categorical or pandas.Index
@@ -1561,17 +1556,6 @@ def map(
         >>> cat.map({"a": "first", "b": "second"}, na_action=None)
         Index(['first', 'second', nan], dtype='object')
         """
-        if na_action is lib.no_default:
-            warnings.warn(
-                "The default value of 'ignore' for the `na_action` parameter in "
-                "pandas.Categorical.map is deprecated and will be "
-                "changed to 'None' in a future version. Please set na_action to the "
-                "desired value to avoid seeing this warning",
-                FutureWarning,
-                stacklevel=find_stack_level(),
-            )
-            na_action = "ignore"
-
         assert callable(mapper) or is_dict_like(mapper)
 
         new_categories = self.categories.map(mapper)

pandas/core/arrays/datetimelike.py

@@ -728,7 +728,7 @@ def _unbox(self, other) -> np.int64 | np.datetime64 | np.timedelta64 | np.ndarra
     #  pandas assumes they're there.
 
     @ravel_compat
-    def map(self, mapper, na_action=None):
+    def map(self, mapper, na_action: Literal["ignore"] | None = None):
         from pandas import Index
 
         result = map_array(self, mapper, na_action=na_action)

pandas/core/arrays/masked.py

@@ -1318,7 +1318,7 @@ def max(self, *, skipna: bool = True, axis: AxisInt | None = 0, **kwargs):
         )
         return self._wrap_reduction_result("max", result, skipna=skipna, axis=axis)
 
-    def map(self, mapper, na_action=None):
+    def map(self, mapper, na_action: Literal["ignore"] | None = None):
         return map_array(self.to_numpy(), mapper, na_action=na_action)
 
     @overload

pandas/core/arrays/sparse/array.py

@@ -1253,7 +1253,7 @@ def astype(self, dtype: AstypeArg | None = None, copy: bool = True):
 
         return self._simple_new(sp_values, self.sp_index, dtype)
 
-    def map(self, mapper, na_action=None) -> Self:
+    def map(self, mapper, na_action: Literal["ignore"] | None = None) -> Self:
         """
         Map categories using an input mapping or function.
 

pandas/core/frame.py

@@ -10369,7 +10369,7 @@ def apply(
         return op.apply().__finalize__(self, method="apply")
 
     def map(
-        self, func: PythonFuncType, na_action: str | None = None, **kwargs
+        self, func: PythonFuncType, na_action: Literal["ignore"] | None = None, **kwargs
     ) -> DataFrame:
         """
         Apply a function to a Dataframe elementwise.

pandas/tests/arrays/categorical/test_map.py

@@ -134,16 +134,3 @@ def test_map_with_dict_or_series(na_action):
     result = cat.map(mapper, na_action=na_action)
     # Order of categories in result can be different
     tm.assert_categorical_equal(result, expected)
-
-
-def test_map_na_action_no_default_deprecated():
-    # GH51645
-    cat = Categorical(["a", "b", "c"])
-    msg = (
-        "The default value of 'ignore' for the `na_action` parameter in "
-        "pandas.Categorical.map is deprecated and will be "
-        "changed to 'None' in a future version. Please set na_action to the "
-        "desired value to avoid seeing this warning"
-    )
-    with tm.assert_produces_warning(FutureWarning, match=msg):
-        cat.map(lambda x: x)