[fix] Ensuring export_pandas returns a pandas.DataFrame (#189)

Author: john-bodley

pydruid/query.py

@@ -198,8 +198,9 @@ def export_pandas(self):
                     "type: {0}".format(self.query_type)
                 )
 
-            df = pandas.DataFrame(nres)
-            return df
+            return pandas.DataFrame(nres)
+
+        return pandas.DataFrame()
 
     def __str__(self):
         return str(self.result)

tests/test_query.py

@@ -243,7 +243,11 @@ def test_export_pandas(self):
         query = create_query_with_results()
         df = query.export_pandas()
         expected_df = pandas.DataFrame(EXPECTED_RESULTS_PANDAS)
-        assert_frame_equal(df, expected_df)
+        assert_frame_equal(df, expected_df, check_like=True)
+
+        query = Query({}, 'timeseries')
+        df = query.export_pandas()
+        assert_frame_equal(df, pandas.DataFrame())
 
     def test_query_acts_as_a_wrapper_for_raw_result(self):
         # given
@@ -253,4 +257,3 @@ def test_query_acts_as_a_wrapper_for_raw_result(self):
         assert len(query) == 2
         assert isinstance(query[0], dict)
         assert isinstance(query[1], dict)
-