added a test

Author: Kully

plotly/grid_objs/grid_objs.py

@@ -151,17 +151,16 @@ def __init__(self, columns_or_json, fid=None):
         """
         # TODO: verify that columns are actually columns
         if pd and isinstance(columns_or_json, pd.DataFrame):
-            column_names = [name for name in columns_or_json.columns]
-            duplicate_name = utils.get_first_duplicate(column_names)
+            duplicate_name = utils.get_first_duplicate(columns_or_json.columns)
             if duplicate_name:
                 err = exceptions.NON_UNIQUE_COLUMN_MESSAGE.format(duplicate_name)
                 raise exceptions.InputError(err)
 
             # create columns from dataframe
             all_columns = []
-            for name in column_names:
+            for name in columns_or_json.columns:
                 all_columns.append(Column(columns_or_json[name].tolist(), name))
-            self._columns = list(all_columns)
+            self._columns = all_columns
             self.id = ''
 
         elif isinstance(columns_or_json, dict):

plotly/tests/test_optional/test_grid/__init__.py

@@ -0,0 +1,32 @@
+"""
+test_grid:
+==========
+
+A module intended for use with Nose.
+
+"""
+from __future__ import absolute_import
+
+from unittest import TestCase
+
+from plotly.exceptions import InputError
+from plotly.grid_objs import Grid
+
+import pandas as pd
+
+
+class Test_Dataframe_to_Grid(TestCase):
+
+    # Test duplicate columns
+    def test_duplicate_columns(self):
+        df = pd.DataFrame([[1, 'a'],
+                           [2, 'b']], columns=['col_1', 'col_1'])
+
+        NON_UNIQUE_COLUMN_MESSAGE = (
+            "Yikes, plotly grids currently "
+            "can't have duplicate column names. Rename "
+            "the column \"{}\" and try again.".format('col_1')
+        )
+
+        with self.assertRaisesRegexp(InputError, NON_UNIQUE_COLUMN_MESSAGE):
+            Grid(df)