Use Python UpdateCursor method to calculate values in a table based on another field

Summary

Instructions provided describe how to use the Python UpdateCursor method to calculate values in a table based on another field.

Sometimes it is desirable to set attributes in a field to certain values based on the value of another field. In this case the UpdateCursor with conditional statements can be used to correctly set those values.

Procedure

Code:
# Import the standard modules and create the geoprocessor...
import arcgisscripting, os, string, sys, time
gp = arcgisscripting.create()

# Set the overwrite to true...
gp.overwriteoutput = 1

# The file to be updated...
fc = r"C:\Temp\testdata.shp"

# Create the UpdateCursor Object
cur = gp.updatecursor(fc)
row = cur.next()

while row:
    # Get the value of the field the calculation will be based on...
    field1 = str(row.getvalue("FIELD1"))
    # Conditional Statements
    # if the field1 = value1, set field2 to equal NewVal1, etc...
    if field1 == "Value1":
        row.FIELD2 = "NewVal1"
        cur.updaterow(row)
        row = cur.next()
    elif field1 == "Value2":
        row.FIELD2 = "NewVal2"
        cur.updaterow(row)
        row = cur.next()
    else:
        row.FIELD2 = "NewVal3"
        cur.updaterow(row)
        row = cur.next()

del cur, row, gp