'If...Then' Code for Field Calculator

JeffreyNemecek

I completed a Model that overlays several polygon layers, clips out a specified section, dissolves according to certain attributes and sums the acreage.  What I want to do is add another Calculate Field entry into my Model, but I can't get the Field Calculation correct.  The Fields I want to select from are [CAUVLCType] and [MUSYM].  The fields are coded-value domains and descriptions.  What I've tried is similar to Label expressions:

Function
if ([CAUVLCType] = 'CROP' AND [MUSYM] = 'NpA') then
[Soil_Acreage] * 460
elseif ([CAUVLCType] = 'WOOD' AND [MUSYM] = 'NpA') then
[Soil_Acreage] * 100
End if
End Function

Can someone provide me a couple lines of code that will work on a copy/paste basis which I can repeat and enter different field descriptions as needed?!

Thanks, Jeff

markdenil

You cannot calculate the field directly in the code block.
You can reference a field, as in your If statement,
But you cannot change a field, even if it is the one you are calculating.

The code block acts like a function (even though it doesn't use Function tags), and has to return the value it is calculating to the calculation expression. That is why the code block is called Pre-Logic Script Code in the Field calculator: it is executed BEFORE the field is calculated.

As in rfairhur24's example, make the codeblok output a variable:
Output = [Soil_Acreage] * 460

Then put the variable (in thios case, Output) in the expression (in the Field Calculator, it is the box below the code block box. The one headed: Soil_Acreage =

In the python code, the output variable goes in the expression parameter
CalculateField_management (in_table, field, expression, {expression_type}, {code_block})
While the code block (that sets the variable to the value you need) is in the code_block variable.