django_example_new.py

class Photo(models.Model):
    photo = models.ImageField(upload_to='photos')

    @set_attributes(short_description='Image', allow_tags=True)
    def image_tag(self):
        if not self.photo:
            return u''
        return u'<img width="100" src="/media/%s" />' % self.photo

django_example_old.py

class Photo(models.Model):
    photo = models.ImageField(upload_to='photos')

    def image_tag(self):
        if not self.photo:
            return u''
        return u'<img width="100" src="/media/%s" />' % self.photo
    image_tag.short_description = 'Image'
    image_tag.allow_tags = True

set_function_attributes.py

def set_attributes(**kwargs):
    def decorator(f):
        for key, value in kwargs.iteritems():
            setattr(f, key, value)
        return f
    return decorator