Check if field is changed before saving entry

When you save entry in Django, how to check, if a field is changed?

Here is simple solution:

class MyModel(models.Model):
    title = models.CharField(max_length=1)

    def save(self, *args, **kw):
        if self.pk is not None:
            orig = MyModel.objects.get(pk=self.pk)
            if orig.title != self.title:
                print 'title is changed'
        super(MyModel, self).save(*args, **kw)