How do I calculate the total number of likes for all of a user's posts in Django?

I’m working on a Django project and I’m trying to calculate the total number of likes for a user based on their posts (i.e if a user has post with 10 likes and another with 5, the total likes must display 15) . I’ve tried various approaches, but I haven’t been able to get it working.

Here is my models.py:

class User(AbstractUser):
    username = models.CharField(...)
    first_name = models.CharField(...)
    last_name = models.CharField(...)
    email = models.EmailField(...)
    bio = models.CharField(...)
    ...

class Post(models.Model):
    author = models.ForeignKey(User, null=True, on_delete=models.SET_NULL)
    text = models.CharField(max_length=280)
    created_at = models.DateTimeField(auto_now_add=True)
    likes = models.ManyToManyField(User, related_name="user_post")

    def total_likes(self):
        return self.likes.count()

    class Meta:
        ordering = ["created_at"]

And here I am trying to display the total number of likes for all posts from a specific user inside this html file (user profile):

...
    <p>Total likes: {{ post.likes.all.count }} </p>
...

views.py

@login_required
def show_user(request, user_id):
    try:
        user = User.objects.get(id=user_id)
        posts = Post.objects.filter(author=user)
    except ObjectDoesNotExist:
        return redirect('user_list')
    else:
        return render(request, 'show_user.html', {'user': user , 'posts' : posts, 'request_user': request.user})
        

Here’s what I’ve tried so far:

1. Initially, I attempted to use the {{ post.likes.all.count }} template tag to display the total number of likes for each post. However, this didn’t work as it didn’t return any value on the screen.

2. Next, I tried using the {% add %} template tag within a loop to iterate over all the posts and accumulate the likes count. However, this resulted in a TemplateSyntaxError.

I am not sure what the best way to solve this issue is. I would greatly appreciate any guidance or suggestions on how to calculate and display the total number of likes for a user’s from all posts in Django.

>Solution :

You can determine the total number of likes for an author with:

from django.db.models import Count


@login_required
def show_user(request, user_id):
    user = get_object_or_404(
        User.objects.annotate(total_likes=Count('post__likes')), pk=user_id
    )
    posts = Post.objects.filter(author=user)
    return render(
        request,
        'show_user.html',
        {'user': user, 'posts': posts, 'request_user': request.user},
    )

in the template you can then render the total likes of the user with:

{{ user.total_likes }}

You can also boost counting the number of likes per post with:

from django.db.models import Count

@login_required
def show_user(request, user_id):
    user = get_object_or_404(
        User.objects.annotate(total_likes=Count('post__likes')), pk=user_id
    )
    posts = Post.objects.annotate(num_likes=Count('likes')).filter(author=user)
    return render(
        request,
        'show_user.html',
        {'user': user, 'posts': posts, 'request_user': request.user},
    )

In the template you can then render this with:

{% for post in posts %}
  {{ post }} (likes: {{ post.num_likes }})
{% endfor %}

Note: It is often better to use get_object_or_404(…) ^[Django-doc],
then to use .get(…) ^[Django-doc] directly. In case the object does not exists,
for example because the user altered the URL themselves, the get_object_or_404(…) will result in returning a HTTP 404 Not Found response, whereas using
.get(…) will result in a HTTP 500 Server Error.

Note: It is normally better to make use of the settings.AUTH_USER_MODEL ^[Django-doc] to refer to the user model, than to use the User model ^[Django-doc] directly. For more information you can see the referencing the User model section of the documentation.