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Way to Filter by DB Field in Django using Class Views

I tried to search for answers, but after a few days, I'm here asking:
I'm a beginner, making a todo list app - expanding on a tutorial I followed. Currently, it's filtering by user, which is fine, but I also want to filter by a field in the DB (list).
Models:
class ToDoList(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE, null=True, blank=True)
title = models.CharField(max_length=200)
description = models.CharField(max_length=200)
created = models.DateTimeField(auto_now_add=True)
def __str__(self):
return self.title
class Meta:
ordering = ['created']
class Task(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE, null=True, blank=True)
title = models.CharField(max_length=200)
description = models.TextField(null=True, blank=True)
complete = models.BooleanField(default=False)
created = models.DateTimeField(auto_now_add=True)
list = models.ForeignKey(ToDoList, on_delete=models.CASCADE)
def __str__(self):
return self.title
class Meta:
ordering = ['complete']
View I'm trying to change:
class TaskList(LoginRequiredMixin, ListView):
model = Task
context_object_name = "tasks"
def get_context_data(self, **kwargs):
context = super().get_context_data(**kwargs)
context['tasks'] = context['tasks'].filter(user=self.request.user)
context['count'] = context['tasks'].filter(complete=False).count
search_input = self.request.GET.get('search-area') or ''
if search_input:
context['tasks'] = context['tasks'].filter(title__startswith=search_input)
context['search_input'] = search_input
return context
Also, is there a way to access the list variable in the html component, like here?
url:
path('tasks/<list>/create', TaskCreate.as_view(), name="task-create"),
html:
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How do I display comments that are using a foreign key of another model in Django class based views?

I would like to list out the comments on my Post Detail page and wanted to see how I can connect a view to the specific comments for a given post?
Models.py
class Post(models.Model):
owner = models.ForeignKey(
Profile, null=True, blank=True, on_delete=models.SET_NULL)
title = models.CharField(max_length=200)
body = models.TextField()
Post_image = models.ImageField(
null=True, blank=True, default='default.jpeg')
create_date = models.DateTimeField(auto_now_add=True)
def __str__(self):
return self.title
def get_absolute_url(self):
return reverse('post', kwargs={'pk': self.pk})
class Meta:
ordering = ['-create_date']
class Comment(models.Model):
owner = models.ForeignKey(Profile, on_delete=models.CASCADE, null=True)
post = models.ForeignKey(Post, on_delete=models.CASCADE)
text = models.TextField()
create_date = models.DateTimeField(auto_now_add=True)
Views.py
class PostDetailView(DetailView):
model = Post
def get_context_data(self, **kwargs):
context = super().get_context_data(**kwargs)
context['comment_list'] = Post.comment_set.all()
return context

You can access the detail object of the DetailView with self.object:
class PostDetailView(DetailView):
model = Post
def get_context_data(self, **kwargs):
context = super().get_context_data(**kwargs)
context['comment_list'] = self.object.comment_set.order_by('create_date')
return context

Django query which calculate most active post by like and dislike, and by each category

I want to calculate most popular post by each category, but i have this error DISTINCT ON fields is not supported by this database backend.
after i use PostgreSql, but I also had a error. annotation and distinct together did not work.
model -->
class Category(models.Model):
title = models.CharField(max_length=150, verbose_name=_("კატეგორია"))
def __str__(self):
return self.title
class Question(models.Model):
user = models.ForeignKey(
User, on_delete=models.CASCADE, verbose_name=_("მომხმარებელი")
)
category = models.ManyToManyField(Category)
title = models.CharField(max_length=150, verbose_name=_("სათაური"))
body = models.TextField(verbose_name=_("ტექსტი"))
image = models.ImageField(blank=True, null=True, verbose_name=_("ფოტო"))
link = models.URLField(
max_length=400,
blank=True,
null=True,
validators=[RequireHttpOrHttpsUrl()],
verbose_name=_("ლინკი"),
)
time = models.DateTimeField(auto_now=True)
send_notification = models.BooleanField(
default=True, verbose_name=_("გავაგზავნოთ შეტყობინება?")
)
def __str__(self):
return self.title
class LikeDislike(models.Model):
user = models.ForeignKey(
User, on_delete=models.CASCADE, verbose_name=_("მომხმარებელი")
)
question = models.ForeignKey(
Question, on_delete=models.CASCADE, verbose_name=_("კითხვა")
)
point = models.BooleanField()
time = models.DateTimeField()
def __str__(self):
return self.question.title
view ->
class CountLikeByCategory(generics.ListCreateAPIView):
serializer_class = CountLikeByCategorySerializer
def get_queryset(self):
query=Question.objects.values_list(
'category__title','title'
).annotate(
l=Count('likedislike',filter=Q(likedislike__point=1)),
d=Count('likedislike',filter=Q(likedislike__point=0)),
total=F('l')+F('d'),
).order_by('category', '-total').distinct('category')
return query
who can help me?
i wan correct query

try this:
def get_queryset(self):
query=Question.objects.values_list(
'category','category__title','title'
).annotate(
l=Count('likedislike',filter=Q(likedislike__point=1)),
d=Count('likedislike',filter=Q(likedislike__point=0)),
total=F('l')+F('d'),
).order_by('category', '-total').distinct('category')
return query

Error : The QuerySet value for an exact lookup must be limited to one result using slicing

I am new to django and am creating a question answer app
I am getting the following error:
The QuerySet value for an exact lookup must be limited to one result using slicing.
models.py:
from django.db import models
from django.contrib.auth.models import User
from django.utils.text import slugify
from django.contrib.auth.models import User
class Log(models.Model):
title = models.CharField(blank=False, max_length=500)
content = models.TextField(blank=False)
created = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
slug = models.SlugField(max_length=50, null=False)
created_by = models.CharField(null=True, max_length=500)
avatar = models.ImageField(
upload_to='images', blank=True)
def save(self, *args, **kwargs):
self.slug = self.slug or slugify(self.title)
super().save(*args, **kwargs)
class Meta:
verbose_name = ("Log")
verbose_name_plural = ("Logs")
def __str__(self):
return f"{self.title}"
class Solutions(models.Model):
log = models.ForeignKey(
Log, on_delete=models.CASCADE, blank=True, null=True)
solution = models.TextField(null=True)
created = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
slug = models.SlugField(max_length=50, null=False, blank=True)
def save(self, *args, **kwargs):
self.slug = self.slug or slugify(self.title)
super().save(*args, **kwargs)
class Meta:
verbose_name = ("Solution")
verbose_name_plural = ("Solutions")
def __str__(self):
return f" {self.log.title} {self.solution} "
class Like(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE)
log = models.ForeignKey(Log, on_delete=models.CASCADE)
created = models.DateTimeField(auto_now_add=True)
def __str__(self):
return f"like by {self.user.username} for {self.log.title}"
class Comments(models.Model):
created = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
log = models.ForeignKey(
Solutions, on_delete=models.CASCADE, null=True, blank=True)
comment = models.TextField(null=True, blank=True)
created_by = models.CharField(null=True, max_length=500)
class Meta:
verbose_name = ("Comment")
verbose_name_plural = ("Comments")
def __str__(self):
return f"{self.comment}"
The error that I am getting is in getting the comments of a particular solution.
The function for that in views.py:
def solution(request, id, question):
solution = Solutions.objects.filter(id=id)
if request.method == 'POST':
form = CommentForm(request.POST)
if form.is_valid():
solution = Solutions.objects.filter(id=id)
com = form.cleaned_data['comment']
c = Comments()
c.comment = com
c.created_by = request.user.username
c.log = solution
print(c)
c.save()
message = messages.add_message(request, 25,
'Comment added successfully')
return HttpResponseRedirect(f'/solution/{id}/{solution.slug}')
else:
message = messages.add_message(request, 30,
'Error')
else:
form = CommentForm()
message = ''
try:
solution = Solutions.objects.filter(id=id)
print(solution)
comment = Comments.objects.filter(log=solution)
except Solutions.DoesNotExist:
comment = ''
solution = ''
context = {
'comments': comment,
'forms': form,
'message': message,
'solution': solution,
}
return render(request, 'solution.html', context=context)
The error is in the line solution = Solutions.objects.filter(id=id)
When I print the solution, it gives me a an empty query set.. Can anyone tell me the right way to do it?
I have a question (log as per in database) and solution to that question.. And the solutions have comments
Thanks

solution = Solutions.objects.get(id=id)
filter returns a QuerySet while get returns an object.

Solution.objects.filter(id=id) returns a QuerySet and it could be emplty if the Solution with such id does not exist. In this case you cannot get an exception you want. Use Solution.objects.get(id=id), then you will get a single instance or the Solutions.DoesNotExist exception.
BTW, id is a bad naming for variable in python, because id is a standard python function.

FieldError django

Please I need help, I dont know where the problem is coming from, please see the code below
#api_view(['GET'])
#permission_classes([IsAuthenticated])
def post_feed_view(request, *args, **kwargs):
user = request.user
profiles = user.follow_user.all()
followed_users_id = []
if profiles.exists():
followed_users_id = [x.user.id for x in profiles]
followed_users_id.append(user.id)
queryset = Post.objects.filter(user__id__in=followed_users_id).order_by("-date_posted")
serializer = PostSerializer(queryset, many=True)
return Response(serializer.data, status=200)
I keep getting this error: Cannot resolve keyword 'user' into field. Choices are: author, author_id,
although, in my models, I dont have "User" what I have is "Author".
But I dont know where exactly to put in author. I think my problem is that i dont fully understand "request.user".
Please help!.
===========
This is the Profile and Follow models:
class Profile(models.Model):
user = models.OneToOneField(User, on_delete=models.CASCADE)
bio = models.CharField(max_length=245, null=True)
image = models.ImageField(default='default.png', upload_to='profile_pics')
interests = models.ManyToManyField(Category, related_name='interests_user')
stripe_customer_id = models.CharField(max_length=50, blank=True, null=True)
one_click_purchasing = models.BooleanField(default=False)
is_vendor = models.BooleanField(default=False)
# vendor
bvn = models.CharField(max_length=10, null=True, blank=True)
description = models.TextField(null=True, blank=True)
address = models.CharField(max_length=200, null=True, blank=True)
company = models.CharField(max_length=100, null=True, blank=True)
# follow_user = models.ManyToManyField('users.Follow')
def __str__(self):
return f'{self.user.username} Profile'
#property
def followers(self):
return Follow.objects.filter(follow_user=self.user).count()
#property
def following(self):
return Follow.objects.filter(user=self.user).count()
def save(self, force_insert=False, force_update=False, using=None,
update_fields=None):
super().save()
img = Image.open(self.image.path)
if img.height > 300 or img.width > 300:
output_size = (300, 300)
img.thumbnail(output_size)
img.save(self.image.path)
class Follow(models.Model):
user = models.ForeignKey(User, related_name='user', on_delete=models.CASCADE)
follow_user = models.ForeignKey(User, related_name='follow_user', on_delete=models.CASCADE)
date = models.DateTimeField(auto_now_add=True)
old_instance = models.ForeignKey('Follow', blank=True, null=True, on_delete=models.CASCADE, editable=False)
def save(self, *args, **kwargs):
if self.pk is not None:
self.old_instance = Follow.objects.get(pk=self.pk)
super().save(*args,**kwargs)
def __str__(self):
return f"For: {self.user} // id: {self.id}"
class FollowerRelation(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE)
profile = models.ForeignKey("Profile", on_delete=models.CASCADE)
timestamp = models.DateTimeField(auto_now_add=True)

Your Post model apparently has no user field, but an author field, so you can filter with:
queryset = Post.objects.filter(
author_id__in=followed_users_id
).order_by('-date_posted')
But that being said, you should not filter like that. Given your models you can do this in a single query and thus avoiding the N+1 problem. You can simply filter with:
#api_view(['GET'])
#permission_classes([IsAuthenticated])
def post_feed_view(request, *args, **kwargs):
queryset = Post.objects.filter(
author__follow_user__user=request.user
).order_by('-date_posted')
serializer = PostSerializer(queryset, many=True)
return Response(serializer.data, status=200)