diff --git a/core/ArchiveExtractor.py b/core/ArchiveExtractor.py
index fa5023000b2c03b7e561d73d2b2da3e8c705de9d..80f952e4d97f467b91ea24f3b8fa94d81b4c52a0 100755
--- a/core/ArchiveExtractor.py
+++ b/core/ArchiveExtractor.py
@@ -10,16 +10,19 @@ import pandas as pd
 __version__ = "1.0.1"
 
 ##########################################################################
-""" Commodity variables """
+""" Commodity private variables """
 
 # Extractor date format for GetAttDataBetweenDates
-DBDFMT = "%Y-%m-%d %H:%M:%S"
+_DBDFMT = "%Y-%m-%d %H:%M:%S"
 
 # Extractor date format for GetNearestValue
-DBDFMT2 = "%d-%m-%Y %H:%M:%S"
+_DBDFMT2 = "%d-%m-%Y %H:%M:%S"
+
+##########################################################################
+""" Commodity private functions """
 
 # Vectorized fromtimestamp function
-ArrayTimeStampToDatetime = np.vectorize(datetime.datetime.fromtimestamp)
+_ArrayTimeStampToDatetime = np.vectorize(datetime.datetime.fromtimestamp)
 
 
 class ArchiveExtractor:
@@ -219,14 +222,14 @@ class ArchiveExtractor:
                 # Inform on retrieval request
                 self.logger.info("Perform ExtractBetweenDates (%s, %s, %s)"%(
                     attribute,
-                    cdates[i_d].strftime(DBDFMT),
-                    cdates[i_d+1].strftime(DBDFMT))
+                    cdates[i_d].strftime(_DBDFMT),
+                    cdates[i_d+1].strftime(_DBDFMT))
                     )
 
                 cmdreturn = self._cmd_with_retry("ExtractBetweenDates", [
                                                         attribute,
-                                                        cdates[i_d].strftime(DBDFMT),
-                                                        cdates[i_d+1].strftime(DBDFMT)
+                                                        cdates[i_d].strftime(_DBDFMT),
+                                                        cdates[i_d+1].strftime(_DBDFMT)
                                                         ])
 
                 # Check command return
@@ -241,7 +244,7 @@ class ArchiveExtractor:
                 # NOTE: it is faster than using pandas.to_datetime()
                 _value = np.asarray(_value, dtype=float)
                 if len(_date) > 0:
-                    _date = ArrayTimeStampToDatetime(_date/1000.0)
+                    _date = _ArrayTimeStampToDatetime(_date/1000.0)
 
                 value.append(_value)
                 date.append(_date)
@@ -250,14 +253,14 @@ class ArchiveExtractor:
             if attrtype=="vector":
                 self.logger.info("Perform GetAttDataBetweenDates (%s, %s, %s)"%(
                                                         attribute,
-                                                        cdates[i_d].strftime(DBDFMT),
-                                                        cdates[i_d+1].strftime(DBDFMT)
+                                                        cdates[i_d].strftime(_DBDFMT),
+                                                        cdates[i_d+1].strftime(_DBDFMT)
                                                         ))
 
                 [N,], [name,] = self.extractor.GetAttDataBetweenDates([
                     attribute,
-                    cdates[i_d].strftime(DBDFMT),
-                    cdates[i_d+1].strftime(DBDFMT)
+                    cdates[i_d].strftime(_DBDFMT),
+                    cdates[i_d+1].strftime(_DBDFMT)
                     ])
                 N=int(N)
 
@@ -396,14 +399,14 @@ class ArchiveExtractor:
                 self.logger.debug("Perform GetAttData%sBetweenDates (%s, %s, %s)"%(
                     func,
                     attribute,
-                    cdates[i_d].strftime(DBDFMT2),
-                    cdates[i_d+1].strftime(DBDFMT2))
+                    cdates[i_d].strftime(_DBDFMT2),
+                    cdates[i_d+1].strftime(_DBDFMT2))
                     )
 
                 _val =getattr(self.extractor, "GetAttData%sBetweenDates"%func)([
                     attribute,
-                    cdates[i_d].strftime(DBDFMT2),
-                    cdates[i_d+1].strftime(DBDFMT2)
+                    cdates[i_d].strftime(_DBDFMT2),
+                    cdates[i_d+1].strftime(_DBDFMT2)
                     ])
 
                 arr[i_d] = _val
@@ -490,8 +493,8 @@ class ArchiveExtractor:
         # Get the number of points
         N=self.extractor.GetAttDataBetweenDatesCount([
                 attribute,
-                dateStart.strftime(DBDFMT2),
-                dateStop.strftime(DBDFMT2)
+                dateStart.strftime(_DBDFMT2),
+                dateStop.strftime(_DBDFMT2)
                 ])
         self.logger.debug("On the period, there is %d entries"%N)