old_contents: from django.db import models
  from exchange.managers import ExchangeRateManager
  from exchange.iso_4217 import code_list
  
  
  class Currency(models.Model):
      """Model holds a currency information for a nationality"""
      code = models.CharField(max_length=3, unique=True)
      name = models.CharField(max_length=64)
  
      class Meta:
          verbose_name_plural = 'currencies'
  
      def __unicode__(self):
          return self.code
  
      def get_numeric_code(self):
          return code_list[self.code]  # Let it raise an exception
  
  
  class ExchangeRate(models.Model):
      """Model to persist exchange rates between currencies"""
      source = models.ForeignKey('exchange.Currency', related_name='rates')
      target = models.ForeignKey('exchange.Currency')
      rate = models.DecimalField(max_digits=12, decimal_places=2)
  
      objects = ExchangeRateManager()
  
      def __unicode__(self):
          return '%s / %s = %s' % (self.source, self.target, self.rate)
  
new_contents: from django.db import models
  from exchange.managers import ExchangeRateManager
  from exchange.iso_4217 import code_list
  
  
  class Currency(models.Model):
      """Model holds a currency information for a nationality"""
      code = models.CharField(max_length=3, unique=True)
      name = models.CharField(max_length=64)
  
      class Meta:
          verbose_name_plural = 'currencies'
  
      def __unicode__(self):
          return self.code
  
      def get_numeric_code(self):
          return code_list[self.code]  # Let it raise an exception
  
  
  class ExchangeRate(models.Model):
      """Model to persist exchange rates between currencies"""
      source = models.ForeignKey('exchange.Currency', related_name='rates')
      target = models.ForeignKey('exchange.Currency')
      rate = models.DecimalField(max_digits=17, decimal_places=8)
  
      objects = ExchangeRateManager()
  
      def __unicode__(self):
          return '%s / %s = %s' % (self.source, self.target, self.rate)
  
subject: change rate field's max digits and decimal places