Field calculator in ArcGIS 10.4 multiline python code

Question

I am trying to use field calculator to calculate a field based on unique types in another field. I had to go for a for loop to add new values. I have 81 classes and every class should be assigned an unique number. I am getting some error in my method. I do not have prior experience of using python code in field calculator. I am sharing my code blocks.

def u_biotope(x):
    u=list(set(x))
    listbt=[]
    count=0
    for i in u:
        btype = count
        listbt.append(count)
        count=count+1
    return listbt
u_biotope( [BIOT1] )

It shows: A field was not found or unbalanced quotation marks

does anyone have any idea, How could I solve this?

Answer 1

In the field calculator, your parser should be set to Python. With "Show Codeblock" checked, your function definition should go in the "Pre-Logic Script Code" and the expression box at the bottom should be populated with:

u_biotype(!BIOT1!)

Your code block should end with the return function as well.

The "Calculate Ranges" example on the ArcGIS help page lays out the python syntax for Calculate Field relatively well.