Passing value from GetParameterAsText to row.getValue()?

Question

I am trying to build a simple tool that concatenate values from two fields, and recording it in newly created field - everything within the same table. This tool should work with any shapefile, concatenate any type of fields and create a field (with name chosen by user). My problem is how to pass value of 'new_field_name" in to row.getValue() (second last row of the code). Or any other ways of doing the same?

import time, arcpy
startTime = time.clock()

print "Start"

shapefile = arcpy.GetParameterAsText(0)
field_name_1 = arcpy.GetParameterAsText(1)
field_name_2 = arcpy.GetParameterAsText(2)
new_field_name = arcpy.GetParameterAsText(3)
new_field_length = arcpy.GetParameterAsText(4)
separator = arcpy.GetParameterAsText(5)
arcpy.env.workspace = shapefile
arcpy.env.overwriteOutput = True

arcpy.AddField_management(shapefile, new_field_name, "Text", "", "", new_field_length)

cur = arcpy.UpdateCursor(shapefile)
for row in cur:
    row.getValue() = (str(row.getValue(field_name_1)) + separator + str(row.getValue(field_name_2)))
    cur.updateRow(row)

Answer 1

If you need to use the plain UpdateCursor, use setValue instead of getValue

cur = arcpy.UpdateCursor(shapefile)
for row in cur:
    newValue = str(row.getValue(field_name_1)) + separator + str(row.getValue(field_name_2))
    row.setValue(new_field_name, newValue)
    cur.updateRow(row)

Cursor syntax gets a little simpler when you can use the da.UpdateCursor:

with arcpy.da.UpdateCursor(shapefile, [field_name_1, field_name_2, new_field_name]) as cursor:
    for row in cursor:
        newValue = str(row[0]) + separator + str(row[1])
        row[2] = newValue
        cursor.updateRow(row)

Answer 2

Try row.setValue for the newly added column in your update cursor.