Question

I’m trying to sort a list of posts where votes have priority over the date.

I have my own app called UserPost and I’m using the django-voting app to do votes.

class UserPost(models.Model):
    user = models.ForeignKey(User)

    datetime = models.DateTimeField(auto_now_add=True)
    text = models.CharField(max_length=255, blank=True)
    is_deleted = models.BooleanField(default=False)
    vote = models.ForeignKey(Vote)

Right now, I’m sorting without votes taking precedence yet:

posts_list = sorted(posts_list, key=attrgetter('datetime'))

What’s the best way to go about this?

Thanks!

Answer 1

Tuples are sorted lexicographically, therefore if you return a tuple for sorted’s key= argument you can sort by votes then by dates:

posts_list = sorted(posts_list, key=lambda post: (Vote.objects.get_score(post)['score'], post.datetime))

Alternatively, you might want to also look at the ordering option in a django Model’s Meta class or the order_by method on django Queryset. They will do the sorting on the database in one query, so can be much faster. Alternatively, you can try the posts_list.get_score_in_bulk() to reduce the number of queries to two (one for posts_list, and one for get_score_in_bulk), like so:

scores = Vote.objects.get_score_in_bulk(posts_list)
posts_list = sorted(posts_list, key=lambda post: (scores[post.id]['score'], post.datetime))