Fix for transpose().transpose() with duplicate keys

#199

tablib/core.py

@@ -895,17 +895,17 @@ class Dataset(object):
         new_headers = [self.headers[0]] + self[self.headers[0]]
 
         _dset.headers = new_headers
-        for column in self.headers:
+        for index, column in enumerate(self.headers):
 
             if column == self.headers[0]:
                 # It's in the headers, so skip it
                 continue
 
             # Adding the column name as now they're a regular column
-            row_data = [column] + self[column]
+            # Use `get_col(index)` in case there are repeated values
+            row_data = [column] + self.get_col(index)
             row_data = Row(row_data)
             _dset.append(row=row_data)
-
         return _dset
 
 

test_tablib.py

@@ -241,7 +241,6 @@ class TablibTestCase(unittest.TestCase):
         # Delete from invalid index
         self.assertRaises(IndexError, self.founders.__delitem__, 3)
 
-
     def test_csv_export(self):
         """Verify exporting dataset object as CSV."""
 
@@ -738,6 +737,15 @@ class TablibTestCase(unittest.TestCase):
         self.assertEqual(second_row,
                    ("gpa",90, 67, 50))
 
+    def test_transpose_multiple_headers(self):
+
+        data = tablib.Dataset()
+        data.headers = ("first_name", "last_name", "age")
+        data.append(('John', 'Adams', 90))
+        data.append(('George', 'Washington', 67))
+        data.append(('John', 'Tyler', 71))
+        self.assertEqual(data.transpose().transpose().dict, data.dict)
+
 
     def test_row_stacking(self):
         """Row stacking."""