Hi Damon,Does each feature class only have one polygon feature? You can use a search cursor to loop through the selected lines and get a sum of a field value. Ex:zonePolys = arcpy.ListFeatureClasses("Zone*") for fc in zonePolys: arcpy.AddField_management(fc,"SumOfValues","DOUBLE") arcpy.MakeFeatureLayer_management("OriginalLayer", "OriginalLayer_Lyr") arcpy.SelectLayerByLocation_management("OriginalLayer_Lyr","INTERSECT",fc) # Calculate the sum of the values in the selected features in OriginalLayer_Lyr with arcpy.da.SearchCursor("OriginalLayer_Lyr", ["Length"]) as cursor: sumValues = 0 for row in cursor: sumValues += row[0] # Take the sum value of the line features field and populate the polygon layer's new SumOfValues field with it arcpy.CalculateField_management(fc,"SumOfValues",sumValues)
You will just need to change the field 'Length' to the field you want to sum.