config/
             models.py={class conf(models.Model):
                               item = models.CharField(max_length=10)
                                preco = models.IntegerField(max_length=6)
                          }
         compra/
                models.py={from config.models import conf
                           class compra(models.Model):
                                item = models.CharField(choices=conf.object.all(),max_length=20)]