Trending tags runner

[makyo]

Should be able to look at tags over the past n days and see what's on the rise, ordered by count of latest descending, probably with a lower threshold. Maybe something like:

today = datetime.date.today()
important_tags = Post.objects.filter(created_at__date=today)\
    .values('tags__tag')\
    .annotate(count=Count('tags__tag'))\
    .filter(count__gt=threshold)
tags = dict([(t['tags__tag'], collections.defaultdict(lambda: 0)) for t in important_tags])
for day in range(0, self.n_days):
    date = today - datetime.timedelta(days=day)
    posts_for_day = Post.objects.filter(tags__tag__in=tags.values())\
        .filter(created_at__date__gt=date - datetime.timedelta(days=day + 1))\
        .filter(created_at__date__lt=date)
    for post in posts_for_day:
        for tag in post.tags:
            if tag.tag in tags:
                tags[tag.tag][str(date)] += 1