Field calculations in Python

Question

Hi there, I have a simple point feature class called 'drillholes' in an 9.3.1 ArcSDE database. This feature class has two numeric fields; one called 'GRND_ELEV' which is fully populated, and 'REF_ELEV' which is only partially populated. I need to create a python script which will select all of the rows where 'REF_ELEV' is not populated and then assign the respective value of 'GRND_ELEV' to those rows. I have used model builder with the 'Calculate Field' tool as a starting point and used the expression REF_ELEV = [GRND_ELEV] where [REF_ELEV] is 'NULL'. Running this script generates the following error: File "D:\scripts\DH_Update\TEST.py" line 22, in gp.calculateFieldManagement arcgisscripting.ExecuteError: ERROR 999999: Error executing function. Expected end of statement. Failed to execute . Any thoughts or directions on where I'm going wrong? # --------------------------------------------------------------------------- # TEST.py # Created on: Wed Jul 11 2012 02:56:01 PM # (generated by ArcGIS/ModelBuilder) # --------------------------------------------------------------------------- # Import system modules import sys, string, os, arcgisscripting # Create the Geoprocessor object gp = arcgisscripting.create() # Load required toolboxes... gp.AddToolbox("D:/Program Files (x86)/ArcGIS/ArcToolbox/Toolboxes/Data Management Tools.tbx") # Local variables... GIS_ADMIN_Drillholes = "Database Connections\GIS_PROD_ADMIN.sde\GIS.ADMIN.GROUNDWATER\GIS.ADMIN.Drillholes" GIS_ADMIN_Drillholes__2_ = "Database Connections\GIS_PROD_ADMIN.sde\GIS.ADMIN.GROUNDWATER\GIS.ADMIN.Drillholes" # Process: Calculate Field... gp.CalculateField_management(GIS_ADMIN_Drillholes__2_, "REF_ELEV", "[GRND_ELEV] where [REF_ELEV] is 'NULL'", "VB", "")

MarcinGasior · Accepted Answer

You don't really need to create model or script to calculate this.
Just use Field Calculator on REF_ELEV field:
Pre-Logic VBA Script Code:Dim outRef as double If Not IsNull( [REF_ELEV] ) Then   outRef = [REF_ELEV]  Else   outRef = [GRND_ELEV]  End If

REF_CODE = 
outRef

Here're some results:
[ATTACH=CONFIG]15945[/ATTACH]

If you prefer Python, it can be done in Calculate Field tool. 
Code Block:def fillGaps(grnd, ref):   if ref:     return ref   else:     return grnd

Expression:
fillGaps( !GRND_ELEV!, str(!REF_ELEV!))

I had a problem with passing NULL values from REF_ELEV field to function, but converting it to string str() works well.
[ATTACH=CONFIG]15947[/ATTACH]