How to tranform a column field into a list using Field Calculator

Question

I'm trying to make a simple field calculation with ArcGIS 9.3:

New field = Old field - Old field(first value)

which in Calculate Field with python code should be

Expression: !Old field! - first

Code Block: list= [AngOriz] first = list[0]

The error is ERROR 000539: Runtime error : name 'AngOriz' is not defined Failed to execute (Calculate Field).

How could I tranform a column field into a list?

Ivano

Answer 1

I'm not certain I understand the problem, but I asked a question here previously about the syntax when using the Python Codeblock. The key misunderstanding I had was that you need to pass in your field names as arguments to the code block. Here is a small example:

and the corresponding part of the attribute table:

In your case, I think the easiest thing would be to make a new field with the value from Old field(first value), and then use that for the calculation. This would not require putting python in the codeblock.