added convert_index utility

stand/adb.py

@@ -35,23 +35,17 @@ class ArcticLibrary:
         except adb.exceptions.NoSuchVersionException:
             df = pd.DataFrame()
 
-        df.index = df.index.view("int64") # adb supports update only for timeseries indexes
-        df.index.name = "run"
-
+        convert_index(df, "int64")
         return df
 
 
     def set_data(self, symbol, df):
-        df.index = df.index.view("datetime64[ns]") # adb supports update only for timeseries indexes
-        df.index.name = "run"
-
+        convert_index(df, "datetime64[ns]")
         self.lib.update(symbol, df)
 
 
     def append_data(self, symbol, df):
-        df.index = df.index.view("datetime64[ns]") # adb supports update only for timeseries indexes
-        df.index.name = "run"
-
+        convert_index(df, "datetime64[ns]")
         self.lib.append(symbol, df)
 
 
@@ -69,5 +63,9 @@ def encode_index(index):
     ts = pd.Timestamp(index) # adb supports update only for timeseries indexes
     return pd.Index([ts], name="run")
 
+def convert_index(df, dtype):
+    df.index = df.index.view(dtype) # adb supports update only for timeseries indexes
+    df.index.name = "run"
+