postcodes.rb

# See http://en.wikipedia.org/wiki/Postcodes_in_Australia

# Postcodes that are used for LVRs and PO boxes only
def australian_postcodes_po_boxes
  nsw = (1000..1999).to_a
  act = (200..299).to_a
  vic = (8000..8999).to_a
  qld = (9000..9999).to_a
  sa = (5800..5999).to_a
  wa = (6800..6999).to_a
  tas = (7800..7999).to_a
  nt = (900..999).to_a

  # Convert integers to strings (postcodes are *not* integers)
  (nsw + act + vic + qld + sa + wa + tas + nt).map { |p| "%04i" % p }
end

# Postcodes that are used for regular street addresses (Not PO boxes and LVRs)
def australian_postcodes_regular
  nsw = (2000..2599).to_a +
        (2619..2898).to_a +
        (2921..2999).to_a
  act = (2600..2618).to_a +
        (2900..2920).to_a
  vic = (3000..3999).to_a
  qld = (4000..4999).to_a
  sa =  (5000..5799).to_a
  wa =  (6000..6797).to_a
  tas = (7000..7799).to_a
  nt =  (800..899).to_a

  # Convert integers to strings (postcodes are *not* integers)
  (nsw + act + vic + qld + sa + wa + tas + nt).map { |p| "%04i" % p }
end

# Returns an array of Australian Postcodes
def australian_postcodes
  australian_postcodes_regular + australian_postcodes_po_boxes
end

p australian_postcodes