Running ArcGIS field calculation using Python with algebraic expression using other field values as variables?

Question

I'm trying to run a field calculation using multiple fields in a table as well as independent numeric values with python code in the field calculator window. I've included the first 7 lines of the code below. I'm not getting any syntax errors, but I'm also not getting any results. The other fields used as variables include: Appraised_Value, Ag_value, and TaxRate_Municipal Not sure how to fix it.

Pre-Logic Script Code:

def Reclass( Exemp_Code_Int ) :
 if (Exemp_Code_Int == '0') :
 return (Appraised_Value / 100) * TaxRate_Municipal
 elif (Exemp_Code_Int == '2') :
 return (Ag_Value / 100) * TaxRate_Municipal
 elif (Exemp_Code_Int == '4') :
 return 0

Codeblock looks like this:

 Reclass( !Exemp_Code_Int! )

Screenshot too: enter image description here

• brock: You need to pass those other fields into the function as arguments. In field calculator you do that by typing !field_name!. In your current method, they are not in scope.

Answer 1

All fields have to be included in the Reclass definition to be used by the calculation.

Reclass(!Exemp_Code_Int!, !Appraised_Value!, !TaxRate_Municipal!, !Ag_Value!, etc.)

Then those variables have to be included in the def of Reclass.

def Reclass(Exemp_Code_Int, Appraised_Value, TaxRate_Municipal, Ag_Value, etc.)

Also, if Exem_Code_Int is actually an integer value, then the logical comparison value cannot be a string. I.e.,

if (Exemp_Code_Int == '0'):

must become:

if (Exemp_Code_Int == 0):

• Paul: +1 about integer/string checking. Similarly @FelixTX83, unless you want floor division (i.e, 5/2 in python returns 2), you need one of your values to be a float. The easiest way is probably to change your code to x/100.0
• FelixTX83: Eureka! Thank you so much Richard Fairhurst! You hit three nails right on the head. I've tried with a small sample and I'll apply it to the rest of the script later today. Thanks again and well done!
• FelixTX83: This is the first question I've ever posted on here, so is there some way to mark this question as answered?
• PolyGeo: @FelixTX83 from the Tour you will learn that the Accept button serves that purpose