influxdata · omki2005 · Sep 22, 2017 · Oct 6, 2017 · Oct 9, 2017 · Oct 9, 2017
@@ -10,6 +10,7 @@
 from collections import defaultdict
 
 import pandas as pd
+import pandas.core.common as pdcom
 import numpy as np
 
 from .client import InfluxDBClient
@@ -343,6 +344,17 @@ def _convert_dataframe_to_lines(self,
                     tag_columns.append(tag)
 
             tag_df = dataframe[tag_columns]
+            for tag_col_i in tag_columns:
+                if pdcom.is_categorical_dtype(tag_df[tag_col_i]):
+                    if '' not in tag_df[tag_col_i].cat.categories:
+                        tag_df[tag_col_i] = (tag_df[tag_col_i].cat.
+                                             add_categories('').
+                                             fillna('').
+                                             astype(str))
+                    else:
+                        tag_df[tag_col_i] = (tag_df[tag_col_i].
+                                             fillna('').
+                                             astype(str))
             tag_df = tag_df.fillna('')  # replace NA with empty string
             tag_df = tag_df.sort_index(axis=1)
             tag_df = self._stringify_dataframe(