If/then python for classifying existing field values to a new field

Question

I'd like to have a tool or quick python script to classify an existing number field to a new text field. For example I have a roads layer that has a type identifier as a coded number and I would like to create a new field that described the number code as text. So say the existing field 'FCODE" had code "210" , and I want to write "Highway" in a new field "Type" and do that for multiple number-text pairs. I could select by attribute and classify that way but it would be nice to do it all in one step.

Answer 1

If you want this as a python script, then you could do something with an update cursor...

inputData = "" #Needs to be the full path
codeField = ""
updateField = ""

with arcpy.da.UpdateCursor(inputData, [codeField, updateField]) as updateRows:
    for row in updateRows:
        if row[0] == "TestValue1":
            row[1] = "NewValue"
        elif #... etc
        else:
            #If you want, put something here to catch any values outside of your test
        updateRows.updateRow(row)

You could also do it in the field calculator using a code block, make sure to check off the python Parser and select "Show Codeblock". In the Code Block box put:

def test(testField):
    if testField == "TestValue1":
        return "NewValue"
    elif testField == "TestValue2"
        return "NewValue2"
    elif #... etc

Then where it says "FIELD NAME =" (the update field) put:

test(!testFieldName!)