解决以下实现的pythonic方法

Question

我的django应用程序有3种型号

class Company(models.Model):

    name = models.CharField(_("Name"), max_length = 100, blank = True, null = True)
    address = models.CharField(_("Address"), max_length = 300, blank = True, null = True)

class WebSite(models.Model):

    WEBSITE_TYPE_CHOICES = (
        ('Google+', 'Google+'),
        ('Facebook', 'Facebook'),
        ('Orkut', 'Orkut'),
    )
    user = models.ForeignKey(User)
    website = models.URLField(blank = True, null = True)
    website_type = models.CharField(max_length = 15, choices = WEBSITE_TYPE_CHOICES, default = 'Google+')
    company = models.ForeignKey(Company, null=True, blank=True)

class Review(models.Model):

    rating = models.FloatField(blank = True, null = True) 
    review = models.TextField(blank = True, null = True)
    company = models.ForeignKey(Company, null=True, blank=True)
    website = models.ForeignKey(Website, null=True, blank=True)

我想显示我的数据，例如

CompanyA：

1. Google-5评论，Avg 3.4
2. Orkut -9篇评论，Avg 4.1
3. Facebook - 12篇评论，Avg 4.3
4. 任何其他-2评论，Avg 2

CompanyB：

1. 谷歌-2评论，Avg 3
2. Facebook -5评论，Avg 4

为此，我做了

    final_list = company_list = []
    websites = Website.objects.select_related().filter(user = user)

    for website in websites:
        company = website.company
        if company is not None and company not in company_list:
            company_list.append(brand)
            company_websites = websites.filter(company = company)
            info = []
            for company_website in company_websites:
                company_type = company_website.website_type
                reviews = Review.objects.filter(company = company, website = company_website)
                no_of_reviews = len(reviews)
                average = reviews.aggregate(Avg('rating'))
                info.append({"type": company_type, "no_of_reviews": no_of_reviews,
                             "average": average['rating__avg']})
            final_list.append({"company": company.name, "stats": info})

代码有两个问题

1. 这浪费了大量的计算。
2. 它还以某种方式在final_list (BUGGY)中追加空列表。

FYI:我相信.annotate()是可以使用的，但我不明白如何根据列使用.annotate(在我的例子中是company__name)。

Answer 1

这会给你数据。

Review.objects.values(company, website__website_type).annotate(review_count=Count('id'), average=Avg('rating')).order_by('company')

使用{%重组%}在模板中输出它。

Answer 2

我还没有测试过这个，它可能不如你收到的另一个答案好，但是万一它有帮助.

companies = Company.objects.all()
company_ratings = []

for company in companies:
    websites = company.website_set.filter(user=user)
    new_data = []

    for website in websites:
        reviews = Reviews.objects.filter(website=website, company=company)
        ratings = [x.rating for x in reviews]
        count = len(ratings)
        new_data.append({'website': website, 'count': count, 
                         'average': float(sum(ratings))/count})

    company_ratings.append({'company':company, 'ratings':new_data})