django-在模板中显示平均值

Question

我正在建立一个博客，用户可以在我的帖子上留下评论/评分。 我想显示该特定帖子的所有评分的平均值。 我怎么做？

models.py

class Post(models.Model):
    STATUS_CHOISES = (

        ('draft', 'Draft'),
        ('published', 'Published'),

        )
    category = models.ForeignKey(Category)
    title = models.CharField(max_length=250)
    slug = models.SlugField(max_length=250, unique=True)
    content = models.TextField()
    seo_title = models.CharField(max_length=250)
    seo_description = models.CharField(max_length=160)
    author = models.ForeignKey(User, related_name='blog_posts', default=settings.AUTH_USER_MODEL)
    published = models.DateTimeField(default=timezone.now)
    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)
    status = models.CharField(max_length=9, choices=STATUS_CHOISES, default='draft')

    def get_absolute_url(self):
        return reverse('blog:post_detail', args=[self.slug])


    def __str__(self):
        return self.title



class Comment(models.Model):
    difficulty_rating_choices = (

        (1, 'Very Easy'),
        (2, 'Easy'),
        (3, 'Moderate'),
        (4, 'Hard'),
        (5, 'Very Hard'),

    )

    workload_rating_choices = (

        (1, 'Very Light'),
        (2, 'Light'),
        (3, 'Moderate'),
        (4, 'Heavy'),
        (5, 'Very Heavy'),

    )

    book_rating_choices = (

        (1, '$'),
        (2, '$$'),
        (3, '$$$'),
        (4, '$$$$'),
        (5, '$$$$$'),

    )

    attendance_rating_choices = (

        (1, 'Not Required'),
        (2, 'Required'),


    )
    post = models.ForeignKey(Post, related_name="comments")
    user = models.CharField(max_length=250)
    email = models.EmailField()
    title = models.CharField(max_length=250)
    body = models.TextField()
    created = models.DateTimeField(auto_now_add=True)
    approved = models.BooleanField(default=False)
    difficulty_rating = models.IntegerField(choices=difficulty_rating_choices)
    workload_rating = models.IntegerField(choices=workload_rating_choices)
    book_rating = models.IntegerField(choices=book_rating_choices)
    attendance_rating = models.IntegerField(choices=attendance_rating_choices)


    def approved(self):
        self.approved = True
        self.save()

    def __str__(self):
        return self.title

views.py

def add_comment(request, slug):
    post = get_object_or_404(Post, slug=slug)
    if request.method == 'POST':
        form = CommentForm(request.POST)
        if form.is_valid():
            comment = form.save(commit=False)
            comment.post = post
            comment.save()
            return redirect('blog:post_detail', slug=post.slug)
    else:
        form = CommentForm()
    template = "blog/post/add_comment.html"
    context = {'form': form}
    return render(request, template, context)

模板

<h1>Difficulty: <h1>
        <h1>Workload: <h1>
        <h1>Book Cost: <h1>
        <h1>Attendance: <h1>

        <hr>
        <h2>{{ post.title }}</h2>
        <p>Written by {{ post.author }} on {{ post.published }}</p>
        <hr>
        {{ post.content|linebreaks }}
        <hr>
        <h2>Comments</h2>
        <p>Total number of comments: {{ post.comments.count }}</p>
        <a href="{% url 'blog:add_comment' slug=post.slug %}">Leave a comment</a>
        {% for comment in post.comments.all %}


            <p>Title: {{ comment.title }}</p>
            <p>Review: {{ comment.body }}</p>
            <p>Date: {{ comment.created }}</p>
            <p>Posted by: {{ comment.user }}</p>
            <p>Difficulty: {{ comment.get_difficulty_rating_display }}</p>
            <p>Workload: {{ comment.get_workload_rating_display }}</p>
            <p>Book Cost: {{ comment.get_book_rating_display }}</p>
            <p>Attencance: {{ comment.get_attendance_rating_display }}</p>
            <hr>

        {% empty %}
            <p>There are no comments yet. Be the first one to comment!</p>

        {% endfor %}

我希望在我的模板顶部显示我的4个标准（difficulty_rating，workload_rating，book_rating，attenance_rating）中每个标准的平均值。 我将如何去做？ 到目前为止，我还无法弄清楚。

这是在模板级别完成的吗？ 我是否需要编辑views.py？ 甚至是模型本身？

Answer 1

您可以在Post模型中编写辅助方法：

from django.db.models import Avg

class Post(models.Model):
    # ...
    def avg_ratings(self):
        return self.comments.aggregate(
            Avg('difficulty_rating'),
            Avg('workload_rating'),
            Avg('book_rating'),
            Avg('attendance_rating'),
        )

然后，您可以在模板中执行以下操作：

{% with avg_ratings=post.avg_ratings %}
    {{ avg_ratings.difficulty_rating__avg }}
    {{ avg_ratings.workload_rating__avg }}
    {{ avg_ratings.book_rating__avg }}
    {{ avg_ratings.attendance_rating__avg }}
{% endwith %}