Using Calculate Field Tool to calculate a value in a table based on another field using Python

In some cases, you may want to calculate a field based on the value of another field. A good example of this would be when you may want to create or calculate domain code values from a description field.

In the following example we are using some Tree data to calculate the Risk_Code associated with the Risk description which can then later be used as a Domain.

• To begin, open the Attribute Table for the data in ArcGIS Pro

• Select applicable field to calculate (i.e. RISK_CODE)
• Right click field (RISK_CODE) > Field Calculator

• Select Python 3 as the Expression Type

Code Block

def calcRiskCode(riskDesc):
     if riskDesc == "High":
         return 1
     elif riskDesc == "Medium":
         return 2
     elif riskDesc == "Low":
         return 3
     else:
         return 0

Expression:

calcRiskCode(!RISK_DESC!)

• Click OK.

For example:

Result:

Further Calculate Field Examples:

https://pro.arcgis.com/en/pro-app/tool-reference/data-management/calculate-field-examples.htm

Sam Pienaar.