new_contents: # -*- coding: utf-8 -*-
  from __future__ import unicode_literals
  
  from django.db import models, migrations
  
  from django_countries import countries
  
  CARRIERS = {
      'Telefonica Digital': [{'Movistar': ['Spain', 'Colombia', 'Venezuela', 'Peru',
                                           'Uruguay', 'Mexico', 'Chile', 'El Salvador',
                                           'Nicaragua', 'Guatemala', 'Costa Rica']},
                             {'Vivo': ['Brazil']},
                             {'O2': ['Germany']}],
      'Deutsche Telekom': [{'T-Mobile': ['Poland', 'Czech Republic', 'Macedonia']},
                           {'Congstar': ['Germany']},
                           {'Telekom': ['Hungary']},
                           {'Cosmote': ['Greece']}],
      'Telenor': [{'Telenor': ['Hugnary', 'Serbia', 'Montenegro']},
                  {'Grameenphone': ['Bangladesh']}],
      'Telecom Italia': [{'TIM': ['Italy']}],
      'America Movil': [{'Telcel': ['Mexico']}],
      'Retailer': [{'E.Leclerc': ['France']}],
      'Snapdeal': [{'Spice': ['India']}],
      'JB Hifi': [{'ZTE': ['Australia']}],
      'Alcatel OneTouch': [{'TCL': ['India']}],
      'www.flicpart.com': [{'ZEN Mobil': ['India']}],
      'Megafon': [{'Megafon': ['Russia']}],
      'Cherry Mobile': [{'Cherry Mobile': ['Philippines']}],
      'Banglalink': [{'Banglalink': ['Bangladesh']}],
      'KDDI': [{'KDDI': ['Japan']}]
  }
  
  
  COUNTRIES_DICT = {v: k for k, v in countries}
  
  
  def remove_carriers(apps, schema_editor):
      Carrier = apps.get_model('main', 'Carrier')
      Carrier.objects.all().delete()
  
  
  def add_carriers(apps, schema_editor):
  
      Carrier = apps.get_model('main', 'Carrier')
      for parent_operator, carriers in CARRIERS.items():
          for carrier_data in carriers:
              for carrier, carrier_countries in carrier_data.items():
                  for carrier_country in carrier_countries:
                      if carrier_country in COUNTRIES_DICT:
                          Carrier.objects.create(parent_operator=parent_operator,
                                                 name=carrier,
                                                 country=COUNTRIES_DICT[carrier_country])
                          continue
      Carrier.objects.create(parent_operator='Other', name='Other')
  
  
  def backwards_method(apps, schema_editor):
      pass
  
  
  class Migration(migrations.Migration):
  
      dependencies = [
          ('main', '0008_auto_20150220_1830'),
      ]
  
      operations = [
          migrations.RunPython(remove_carriers, backwards_method),
          migrations.RunPython(add_carriers, remove_carriers),
      ]
  
subject: Add a list of carriers in the app.