BUG: Ignore style column headers when None

Author: HHammond

pandas/core/style.py

@@ -216,7 +216,7 @@ def _translate(self):
                                "class": " ".join(cs)})
             head.append(row_es)
 
-        if self.data.index.names:
+        if self.data.index.names and self.data.index.names != [None]:
             index_header_row = []
 
             for c, name in enumerate(self.data.index.names):

pandas/tests/test_style.py

@@ -129,6 +129,27 @@ def test_set_properties_subset(self):
         expected = {(0, 0): ['color: white']}
         self.assertEqual(result, expected)
 
+    def test_empty_index_name_doesnt_display(self):
+        # https://github.com/pydata/pandas/pull/12090#issuecomment-180695902
+        df = pd.DataFrame({'A': [1, 2], 'B': [3, 4], 'C': [5, 6]})
+        result = df.style._translate()
+
+        expected = [[{'class': 'blank', 'type': 'th', 'value': ''},
+                     {'class': 'col_heading level0 col0',
+                      'display_value': 'A',
+                      'type': 'th',
+                      'value': 'A'},
+                     {'class': 'col_heading level0 col1',
+                      'display_value': 'B',
+                      'type': 'th',
+                      'value': 'B'},
+                     {'class': 'col_heading level0 col2',
+                      'display_value': 'C',
+                      'type': 'th',
+                      'value': 'C'}]]
+
+        self.assertEqual(result['head'], expected)
+
     def test_index_name(self):
         # https://github.com/pydata/pandas/issues/11655
         df = pd.DataFrame({'A': [1, 2], 'B': [3, 4], 'C': [5, 6]})