Calculating field on if-else-condition checking input parameters for <Null>?

Question

I want to calculate a field depending on 3 input string parameters. Two of them can contain Null-values. My old VB expression was not able to work with Null-values, so the script stopped.

Now I want to develop a script which allows me to solve all my problems:

1. set an if-else-condition
2. calculate the field with Python expressions instead VB
3. eliminate Null-values by not computing/using these cells in the expression.

This is the input table to get my parameters

And here is my script:

import arcpy, os
from arcpy import env
 
#Get Parameters
importfeature = arcpy.GetParameter(0)
workspace = arcpy.GetParameter(1)
owner = arcpy.GetParameter(2)
criteria = arcpy.GetParameter(3)
keep_fieldname1 = arcpy.GetParameter(4)
keep_fieldname2 = arcpy.GetParameter(5)

#Set Workspace
arcpy.env.workspace = workspace

#Add Field
arcpy.AddField_management (importfeature, criteria, "text")   

#Calculate field criteria
if keep_fieldname1 == None and keep_fieldname2 == None:
  expression = '"%owner%"'
elif keep_fieldname2 == None
  expression = '"%owner%" +" - "+ !%keep_fieldname1%!'
else
  expression = '"%owner%" +" - "+ !%keep_fieldname1%! +" - "+ !%keep_fieldname2%!'
arcpy.CalculateField_management (importfeature, criteria, expression , "Python")

I need to say that the parameters are automatically given by an iterator to the script via "get values". So don't worry about the input. This is working fine.

How do I solve my problems?

Answer 1

You appear to be treating your variables in your script e.g. owner as inline model variables by surrounding them with %%. That syntax is for accessing variables in a model. You want to set your expression to something like:

expression = '"' + owner + '"'

Also set the expression type from PYTHON to PYTHON_9.3 in the Calculate Field tool.