The QuerySet value for an exact lookup must be limited to one result using slicing - Django

Question

I'm building a news website. While I tried to get the list of relative news which have the same tags. The error said:

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

I have two models News and Tag. Tag is a many-to-many foreign key of News.

# "models.py"

class Tag(models.Model):
    name = models.CharField(max_length=40)

class News(models.Model):
    tag = models.ManyToManyField(Tag, blank=True, verbose_name='tag')

View:

def newsDetailView(request, news_pk):
    news = get_object_or_404(News, id=news_pk)
    tags = news.tag.annotate(news_count=Count('news'))
    relative_news = News.objects.filter(tag=tags)

    return render(request, "news_detail.html", {
        'news': news,
        'tags': tags,
        'relative_news': relative_news
    })

Answer 1

The following will work:

def newsDetailView(request, news_pk):
    news = get_object_or_404(News, id=news_pk)
    relative_news = News.objects.filter(tag__id__in=news.tag.all())

Answer 2

Generally this error occurs when we use model queryset at the place of django models object. In the given question you have done the same. "Objects.filter" returns the model query set there can be single or multiple django model objects, but "objects.get" returns single django model object. Or we can use .last() and .first() with "objects.filter".

Answer 3

this error rises if you use queryset or list in your filter params. For example,

News.objects.filter(title = a)

and here if "a" inside a filter is a queryset or list, then this error raises.

Answer 4

The problem you are facing is that you first take a filter queryset (a collection of objects from your database) for example: Book.objects.filter(subject='fiction') ) and then you are trying to use that filter as a parameter (like subject = 'fiction' in the previous one ) to obtain another filter queryset.

Instead you have to use an object using 'get' instead of 'filter' that is the previous example would become

book = Book.objects.get(subject='fiction')

and then use that object as parameter for next filter.

example: Book_shelf = BookShelf.objects.filter(book = book)

Answer 5

I also experienced the same issue, try doing this, instead of:

relative_news = News.objects.filter(tag=tags)

to

relative_news = News.objects.filter(tag=tags).first()

Answer 6

I got the same error below:

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

Because I assigned the queryset made by filter() to category as shown below:

                       # Here                   # Here                 
Product.objects.filter(category=Category.objects.filter(pk=1))

So, I put __in after category as shown below, then the error was solved:

                              # ↓ Here
Product.objects.filter(category__in=Category.objects.filter(pk=1))

Or, I assigned the object made by get() to category as shown below, then the error was solved:

                                                # Here                 
Product.objects.filter(category=Category.objects.get(pk=1))

Answer 7

YOU CAN DO LIKE THIS list_inst=[]

for i in list_Series:
    list_inst += Episodes.objects.filter(id_serie=i.id_serie)
    
list_Episodes=list_inst