ENH: check for duplicate level names, GH #280

Author: wesm

pandas/core/index.py

@@ -889,6 +889,11 @@ def __iter__(self):
 
     def _get_level_number(self, level):
         if not isinstance(level, int):
+            count = self.names.count(level)
+            if count > 1:
+                raise Exception('The name %s occurs multiple times, use a '
+                                'level number' % level)
+
             level = self.names.index(level)
         elif level < 0:
             level += self.nlevels

pandas/tests/test_index.py

@@ -601,6 +601,10 @@ def test_constructor_single_level(self):
     def test_constructor_no_levels(self):
         self.assertRaises(Exception, MultiIndex, levels=[], labels=[])
 
+    def test_duplicate_names(self):
+        self.index.names = ['foo', 'foo']
+        self.assertRaises(Exception, self.index._get_level_number, 'foo')
+
     def test_from_arrays(self):
         arrays = []
         for lev, lab in zip(self.index.levels, self.index.labels):