BUG: .rename* not treating Series as mapping

doc/source/whatsnew/v0.18.1.txt

@@ -89,3 +89,8 @@ Bug Fixes
 ~~~~~~~~~
 
 - Bug in ``value_counts`` when ``normalize=True`` and ``dropna=True`` where nulls still contributed to the normalized count (:issue:`12558`)
+
+
+- Bug in ``Series.rename``, ``DataFrame.rename`` and ``DataFrame.rename_axis`` not treating ``Series`` as mappings to relabel (:issue:`12623`).
+
+

pandas/core/generic.py

@@ -700,12 +700,9 @@ def rename_axis(self, mapper, axis=0, copy=True, inplace=False):
         1    2  5
         2    3  6
         """
-        is_scalar_or_list = (
-            (not com.is_sequence(mapper) and not callable(mapper)) or
-            (com.is_list_like(mapper) and not com.is_dict_like(mapper))
-        )
-
-        if is_scalar_or_list:
+        non_mapper = lib.isscalar(mapper) or (com.is_list_like(mapper) and not
+                                              com.is_dict_like(mapper))
+        if non_mapper:
             return self._set_axis_name(mapper, axis=axis)
         else:
             axis = self._get_axis_name(axis)

pandas/core/series.py

@@ -8,7 +8,6 @@
 
 import types
 import warnings
-from collections import MutableMapping
 
 from numpy import nan, ndarray
 import numpy as np
@@ -2331,11 +2330,9 @@ def align(self, other, join='outer', axis=None, level=None, copy=True,
 
     @Appender(generic._shared_docs['rename'] % _shared_doc_kwargs)
     def rename(self, index=None, **kwargs):
-        is_scalar_or_list = (
-            (not com.is_sequence(index) and not callable(index)) or
-            (com.is_list_like(index) and not isinstance(index, MutableMapping))
-        )
-        if is_scalar_or_list:
+        non_mapping = lib.isscalar(index) or (com.is_list_like(index) and
+                                              not com.is_dict_like(index))
+        if non_mapping:
             return self._set_name(index, inplace=kwargs.get('inplace'))
         return super(Series, self).rename(index=index, **kwargs)
 

pandas/tests/series/test_alter_axes.py

@@ -55,6 +55,13 @@ def test_rename(self):
         renamed = renamer.rename({})
         self.assertEqual(renamed.index.name, renamer.index.name)
 
+    def test_rename_by_series(self):
+        s = Series(range(5), name='foo')
+        renamer = Series({1: 10, 2: 20})
+        result = s.rename(renamer)
+        expected = Series(range(5), index=[0, 10, 20, 3, 4], name='foo')
+        tm.assert_series_equal(result, expected)
+
     def test_rename_set_name(self):
         s = Series(range(4), index=list('abcd'))
         for name in ['foo', ['foo'], ('foo',)]:

pandas/tests/test_generic.py

@@ -88,21 +88,53 @@ def _compare(self, result, expected):
     def test_rename(self):
 
         # single axis
+        idx = list('ABCD')
+        # relabeling values passed into self.rename
+        args = [
+            str.lower,
+            {x: x.lower() for x in idx},
+            Series({x: x.lower() for x in idx}),
+        ]
+
         for axis in self._axes():
-            kwargs = {axis: list('ABCD')}
+            kwargs = {axis: idx}
             obj = self._construct(4, **kwargs)
 
-            # no values passed
-            # self.assertRaises(Exception, o.rename(str.lower))
-
-            # rename a single axis
-            result = obj.rename(**{axis: str.lower})
-            expected = obj.copy()
-            setattr(expected, axis, list('abcd'))
-            self._compare(result, expected)
+            for arg in args:
+                # rename a single axis
+                result = obj.rename(**{axis: arg})
+                expected = obj.copy()
+                setattr(expected, axis, list('abcd'))
+                self._compare(result, expected)
 
         # multiple axes at once
 
+    def test_rename_axis(self):
+        idx = list('ABCD')
+        # relabeling values passed into self.rename
+        args = [
+            str.lower,
+            {x: x.lower() for x in idx},
+            Series({x: x.lower() for x in idx}),
+        ]
+
+        for axis in self._axes():
+            kwargs = {axis: idx}
+            obj = self._construct(4, **kwargs)
+
+            for arg in args:
+                # rename a single axis
+                result = obj.rename_axis(arg, axis=axis)
+                expected = obj.copy()
+                setattr(expected, axis, list('abcd'))
+                self._compare(result, expected)
+            # scalar values
+            for arg in ['foo', None]:
+                result = obj.rename_axis(arg, axis=axis)
+                expected = obj.copy()
+                getattr(expected, axis).name = arg
+                self._compare(result, expected)
+
     def test_get_numeric_data(self):
 
         n = 4