DOC: updated inline documentation for key sorting

Author: jacobaustin123

pandas/core/frame.py

@@ -4817,9 +4817,8 @@ def sort_index(
         elif isinstance(labels, ABCMultiIndex):
             from pandas.core.sorting import lexsort_indexer
 
-            codes = labels._get_codes_for_sorting()
             indexer = lexsort_indexer(
-                codes,
+                labels._get_codes_for_sorting(),
                 orders=ascending,
                 na_position=na_position,
             )

pandas/core/series.py

@@ -2913,6 +2913,9 @@ def sort_values(
         na_position : {'first' or 'last'}, default 'last'
             Argument 'first' puts NaNs at the beginning, 'last' puts NaNs at
             the end.
+        key : function, default None
+            If not None, apply the key function to every value before
+            sorting. Identical to key argument in built-in sorted function.
 
         Returns
         -------
@@ -2995,6 +2998,22 @@ def sort_values(
         2    d
         0    z
         dtype: object
+        
+        >>> s = pd.Series(['a', 'B', 'c', 'D', 'e'])
+        >>> s.sort_values()
+        1    B
+        3    D
+        0    a
+        2    c
+        4    e
+        dtype: object
+        >>> s.sort_values(key=str.lower)
+        0    a
+        1    B
+        2    c
+        3    D
+        4    e
+        dtype: object
         """
         inplace = validate_bool_kwarg(inplace, "inplace")
         # Validate the axis parameter
@@ -3100,6 +3119,9 @@ def sort_index(
         sort_remaining : bool, default True
             If True and sorting by level and index is multilevel, sort by other
             levels too (in order) after sorting by specified level.
+        key : function, default None
+            If not None, apply the key function to every index element before
+            sorting. Identical to key argument in built-in sorted function.
 
         Returns
         -------
@@ -3182,7 +3204,20 @@ def sort_index(
         baz  two    5
         bar  two    7
         dtype: int64
+
+        >>> s = Series([1, 2, 3, 4, 5, 6, 7, 8])
+        >>> s.sort_index(key=lambda x : -x)
+        7    8
+        6    7
+        5    6
+        4    5
+        3    4
+        2    3
+        1    2
+        0    1
+        dtype: int64
         """
+
         # TODO: this can be combined with DataFrame.sort_index impl as
         # almost identical
         inplace = validate_bool_kwarg(inplace, "inplace")
@@ -3202,10 +3237,9 @@ def sort_index(
             from pandas.core.sorting import lexsort_indexer
 
             labels = index._sort_levels_monotonic()
-            codes = labels._get_codes_for_sorting()
 
             indexer = lexsort_indexer(
-                codes,
+                labels._get_codes_for_sorting(),
                 orders=ascending,
                 na_position=na_position,
             )