simplity implementation

Author: topper-123

doc/source/whatsnew/v2.1.0.rst

@@ -41,7 +41,7 @@ Other enhancements
 - Improved error message when creating a DataFrame with empty data (0 rows), no index and an incorrect number of columns. (:issue:`52084`)
 - :meth:`arrays.SparseArray.map` now supports ``na_action`` (:issue:`52096`).
 - :meth:`Categorical.map` and :meth:`CategoricalIndex.map` now have a ``na_action`` parameter (:issue:`44279`)
--
+
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_210.notable_bug_fixes:

pandas/core/arrays/categorical.py

@@ -1294,18 +1294,18 @@ def map(
 
         new_categories = self.categories.map(mapper)
 
-        not_dictlike_and_no_nans = not (is_dict_like(mapper) and np.nan not in mapper)
+        has_nans = np.any(self._codes == -1)
 
-        if na_action is None and not_dictlike_and_no_nans and np.any(self._codes == -1):
-            na_value = mapper(np.nan) if callable(mapper) else mapper[np.nan]
-            new_categories = new_categories.insert(len(new_categories), na_value)
-            return np.take(new_categories, self._codes)
-        elif new_categories.is_unique and not new_categories.hasnans:
+        na_val = np.nan
+        if na_action is None and has_nans:
+            na_val = mapper(np.nan) if callable(mapper) else mapper.get(np.nan, np.nan)
+
+        if new_categories.is_unique and not new_categories.hasnans and na_val is np.nan:
             new_dtype = CategoricalDtype(new_categories, ordered=self.ordered)
             return self.from_codes(self._codes.copy(), dtype=new_dtype)
 
-        if np.any(self._codes == -1):
-            new_categories = new_categories.insert(len(new_categories), np.nan)
+        if has_nans:
+            new_categories = new_categories.insert(len(new_categories), na_val)
 
         return np.take(new_categories, self._codes)