BUG: ix should return a Series for duplicate indices

pandas/core/indexing.py

@@ -36,6 +36,18 @@ class IndexingError(Exception):
     pass
 
 
+def _reconstruct_from_dup_ix(key, obj, values):
+    if np.isscalar(values):
+        return values
+    assert len(key) == obj.ndim
+
+    kwargs = dict()
+    for axis, name in obj._AXIS_NAMES.items():
+        index = getattr(obj, name)
+        kwargs[name] = index[index.get_loc(key[axis])]
+    return obj._constructor(values, **kwargs).squeeze()
+
+
 class _NDFrameIndexer(object):
     _valid_types = None
     _exception = KeyError
@@ -61,7 +73,8 @@ def __iter__(self):
     def __getitem__(self, key):
         if type(key) is tuple:
             try:
-                return self.obj.get_value(*key)
+                values = self.obj.get_value(*key)
+                return _reconstruct_from_dup_ix(key, self.obj, values)
             except Exception:
                 pass
 
@@ -1101,8 +1114,6 @@ class _IXIndexer(_NDFrameIndexer):
     """ A primarily location based indexer, with integer fallback """
 
     def _has_valid_type(self, key, axis):
-        ax = self.obj._get_axis(axis)
-
         if isinstance(key, slice):
             return True
 

pandas/tests/test_indexing.py

@@ -3570,8 +3570,14 @@ def test_float_index_to_mixed(self):
                                          'a': [10] * 10}),
                               df)
 
+    def test_duplicate_ix_returns_series(self):
+        df = DataFrame(np.random.randn(3, 3), index=[0.1, 0.2, 0.2],
+                       columns=list('abc'))
+        r = df.ix[0.2, 'a']
+        e = df.loc[0.2, 'a']
+        tm.assert_series_equal(r, e)
+
 
 if __name__ == '__main__':
-    import nose
     nose.runmodule(argv=[__file__, '-vvs', '-x', '--pdb', '--pdb-failure'],
                    exit=False)