fix uints

Author: jreback

pandas/core/indexes/base.py

@@ -2910,6 +2910,7 @@ def map(self, mapper, na_action=None):
         from .multi import MultiIndex
         new_values = super(Index, self)._map_values(
             mapper, na_action=na_action)
+
         attributes = self._get_attributes_dict()
         if new_values.size and isinstance(new_values[0], tuple):
             if isinstance(self, MultiIndex):
@@ -2923,8 +2924,14 @@ def map(self, mapper, na_action=None):
 
         attributes['copy'] = False
 
-        # we infer the result types based on the
-        # returned values
+        # we want to try to return our original dtype
+        # ints infer to integer, but if we have
+        # uints, would prefer to return these
+        if is_unsigned_integer_dtype(self.dtype):
+            inferred = lib.infer_dtype(new_values)
+            if inferred == 'integer':
+                attributes['dtype'] = self.dtype
+
         return Index(new_values, **attributes)
 
     def isin(self, values, level=None):

pandas/tests/indexes/common.py

@@ -1007,16 +1007,11 @@ def test_searchsorted_monotonic(self, indices):
                 indices._searchsorted_monotonic(value, side='left')
 
     def test_map(self):
+        # callable
         index = self.create_index()
-
-        # From output of UInt64Index mapping can't infer that we
-        #   shouldn't default to Int64
-        if isinstance(index, UInt64Index):
-            expected = Index(index.values.tolist())
-        else:
-            expected = index
-
-        tm.assert_index_equal(index.map(lambda x: x), expected)
+        expected = index
+        result = index.map(lambda x: x)
+        tm.assert_index_equal(result, expected)
 
     @pytest.mark.parametrize(
         "mapper",
@@ -1028,13 +1023,7 @@ def test_map_dictlike(self, mapper):
         index = self.create_index()
         if isinstance(index, pd.CategoricalIndex):
             pytest.skip("tested in test_categorical")
-
-        # From output of UInt64Index mapping can't infer that we
-        #   shouldn't default to Int64
-        if isinstance(index, UInt64Index):
-            expected = Index(index.values.tolist())
-        else:
-            expected = index
+        expected = index
 
         identity = mapper({x: x for x in index}, index)
         result = index.map(identity)

pandas/tests/indexes/test_base.py

@@ -852,11 +852,15 @@ def test_map_tseries_indices_return_index(self):
         exp = Index(range(24), name='hourly')
         tm.assert_index_equal(exp, date_index.map(lambda x: x.hour))
 
-    def test_map_with_dict_and_series(self):
+    @pytest.mark.parametrize(
+        "mapper",
+        [
+            lambda values, index: {i: e for e, i in zip(values, index)},
+            lambda values, index: pd.Series(values, index)])
+    def test_map_dictlike(self, mapper):
         # GH 12756
         expected = Index(['foo', 'bar', 'baz'])
-        mapper = Series(expected.values, index=[0, 1, 2])
-        result = tm.makeIntIndex(3).map(mapper)
+        result = tm.makeIntIndex(3).map(mapper(expected.values, [0, 1, 2]))
         tm.assert_index_equal(result, expected)
 
         for name in self.indices.keys():
@@ -867,21 +871,16 @@ def test_map_with_dict_and_series(self):
                 # Cannot map duplicated index
                 continue
 
-            cur_index = self.indices[name]
-            expected = Index(np.arange(len(cur_index), 0, -1))
-            mapper = pd.Series(expected, index=cur_index)
-            result = cur_index.map(mapper)
-
-            tm.assert_index_equal(result, expected)
-
-            # If the mapper is empty the expected index type is Int64Index
-            # but the output defaults to Float64 so I treat it independently
-            mapper = {o: n for o, n in
-                      zip(cur_index, expected)}
+            index = self.indices[name]
+            expected = Index(np.arange(len(index), 0, -1))
 
-            result = cur_index.map(mapper)
-            if not mapper:
+            # to match proper result coercion for uints
+            if name == 'uintIndex':
+                expected = expected.astype('uint64')
+            elif name == 'empty':
                 expected = Float64Index([])
+
+            result = index.map(mapper(expected, index))
             tm.assert_index_equal(result, expected)
 
     def test_map_with_non_function_missing_values(self):