def __set__(self, instance, value):
    if instance is None:
        raise AttributeError('%s must be accessed via instance' % self.
            related.opts.object_name)
instance.field1, instance.field2 = value.split('/')

def to_python(self, value):
    return value


class A(models.Model):
    field1 = models.TextField()
Convert property to django model field