I am using ArcGIS 10.3 version in desktop. I wanted to assign landuse names (Landuse_04 column) based on the codes those are in my attribute table as the column ID_MAP. once I am done with editing the script in python, field calculator, this dialogue box is appearing! I do not have any idea about python or programming just worked on a prepared script.

Does anyone know why is this occurring?

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1 Answer 1


It looks like you put the defined function into the returned field. The message says if you have multi-line you have to cut the code and activate the Show codeblock and paste the code into the "Pre-Logic" Script Code space. The last line should be used to return the defined function exist in the "Pre-Logic" Script Code.

Check "Using code blocks" in the Calculate Field examples for more information.

Here is a code snippet from the above help

Code Block:
def Reclass(WellYield):
    if (WellYield >= 0 and WellYield <= 10):
        return 1
    elif (WellYield > 10 and WellYield <= 20):
        return 2
    elif (WellYield > 20 and WellYield <= 30):
        return 3
    elif (WellYield > 30):
        return 4


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