Assigning values to field using if/then logic involving multiple fields

Question

I want to run a field calculation on a string field named [territory] that first looks at a string field [majr_src] to see if there is a value other than "NONE", if so [territory] = [majr_src]. If not, it looks at field [top_pct] to see if it is >30, if so [territory] is assigned the value of another string field called [Top_src]. Finally, if neither of these conditions are met it assigns [Territory] the value from a final string field called [Close_src]

I have: Pre-Logic Script Code:

def selectter(n):
 if [Majr_src] != "NONE":
  n = "[Majr_src]"
 else:
  if [Top_pct] > 30:
   n = "[Top_src]"
  else:
   n = "[Close_src]"

and

Territory =
 selectter([Territory])

I am using ArcMap 10.1

Answer 1

Make sure that you have set your parser to Python (as suggested by @Arabella) and then try something more like this untested code:

Pre-Logic Script Code:

def selectter(Majr_src,Top_pct,Top_src,Close_src):
 if Majr_src != "NONE":
  return Majr_src
 else:
  if Top_pct > 30:
   return Top_src
  else:
   return Close_src

and Territory =

selectter(!Majr_src!,!Top_pct!,!Top_src!,!Close_src!)

A key to understanding how code blocks work in the Field Calculator is learning how to use Python functions.