make map on time tseries indices return index if dtype of output is not a tseries; sphinx changes; fix docstring

Author: nateyoder

doc/source/whatsnew/v0.20.0.txt

@@ -92,26 +92,26 @@ Backwards incompatible API changes
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 -  ``map`` on an ``Index`` now returns an ``Index``, not an array (:issue:`12766`)
-.. ipython:: python
 
-   idx = Index([1, 2])
-   idx
+  .. ipython:: python
 
-Previous Behavior:
+     idx = Index([1, 2])
+     idx
 
-.. code-block:: ipython
+  Previous Behavior:
 
-   In [3]: idx.map(lambda x: x * 2)
-   Out[3]: array([2, 4])
+  .. code-block:: ipython
 
-New Behavior:
+     In [3]: idx.map(lambda x: x * 2)
+     Out[3]: array([2, 4])
 
-.. ipython:: python
+  New Behavior:
 
-    idx.map(lambda x: x * 2)
+  .. ipython:: python
 
-.. _whatsnew_0200.api:
+      idx.map(lambda x: x * 2)
 
+  .. _whatsnew_0200.api:
 
 - ``CParserError`` has been renamed to ``ParserError`` in ``pd.read_csv`` and will be removed in the future (:issue:`12665`)
 - ``SparseArray.cumsum()`` and ``SparseSeries.cumsum()`` will now always return ``SparseArray`` and ``SparseSeries`` respectively (:issue:`12855`)

pandas/indexes/base.py

@@ -2439,7 +2439,8 @@ def map(self, mapper):
         -------
         applied : Index
             The output of the mapping function applied to the index.
-            If the function returns a tuple a
+            If the function returns a tuple with more than one element
+            a MultiIndex will be returned.
         """
         from .multi import MultiIndex
         mapped_values = self._arrmap(self.values, mapper)

pandas/tests/indexes/test_base.py

@@ -772,25 +772,43 @@ def test_map_identity_mapping(self):
         for name, cur_index in self.indices.items():
             self.assert_index_equal(cur_index, cur_index.map(lambda x: x))
 
-    def test_map_that_returns_tuples_creates_multi_index(self):
+    def test_map_with_tuples(self):
         # GH 12766
-        boolean_index = tm.makeIntIndex(3).map(lambda x: (x, x == 1))
-        expected = MultiIndex.from_tuples([(0, False), (1, True), (2, False)])
+
+        # Test that returning a single tuple from an Index
+        #   returns an Index.
+        boolean_index = tm.makeIntIndex(3).map(lambda x: (x,))
+        expected = Index([(0,), (1,), (2,)])
         self.assert_index_equal(boolean_index, expected)
 
-    def test_map_that_returns_a_length_one_tuple_creates_an_index(self):
-        # GH 12766
-        boolean_index = tm.makeIntIndex(3).map(lambda x: (x, ))
-        expected = Index([(0, ), (1, ), (2, )])
+        # Test that returning a tuple from a map of a single index
+        #   returns a MultiIndex object.
+        boolean_index = tm.makeIntIndex(3).map(lambda x: (x, x == 1))
+        expected = MultiIndex.from_tuples([(0, False), (1, True), (2, False)])
         self.assert_index_equal(boolean_index, expected)
 
-    def test_map_that_reduces_multi_index_to_single_index_returns_index(self):
-        # GH 12766
+        # Test that returning a single object from a MultiIndex
+        #   returns an Index.
         first_level = ['foo', 'bar', 'baz']
         multi_index = MultiIndex.from_tuples(lzip(first_level, [1, 2, 3]))
         reduced_index = multi_index.map(lambda x: x[0])
         self.assert_index_equal(reduced_index, Index(first_level))
 
+    def test_map_tseries_indices_return_index(self):
+        date_index = tm.makeDateIndex(10)
+        exp = Index([1] * 10)
+        self.assert_index_equal(exp, date_index.map(lambda x: 1))
+
+        period_index = tm.makePeriodIndex(10)
+        self.assert_index_equal(exp, period_index.map(lambda x: 1))
+
+        tdelta_index = tm.makeTimedeltaIndex(10)
+        self.assert_index_equal(exp, tdelta_index.map(lambda x: 1))
+
+        date_index = tm.makeDateIndex(24, freq='h', name='hourly')
+        exp = Index(range(24), name='hourly')
+        self.assert_index_equal(exp, date_index.map(lambda x: x.hour))
+
     def test_append_multiple(self):
         index = Index(['a', 'b', 'c', 'd', 'e', 'f'])
 

pandas/tseries/base.py

@@ -330,11 +330,11 @@ def _nat_new(self, box=True):
     def map(self, f):
         try:
             result = f(self)
-            if not isinstance(result, (np.ndarray, Index)):
+            if not isinstance(result, Index):
                 raise TypeError
             return result
         except Exception:
-            return _algos.arrmap_object(self.asobject.values, f)
+            return self.asobject.map(f)
 
     def sort_values(self, return_indexer=False, ascending=True):
         """