Ggtcf

I have 2 models, Company and Product, with Product having a ForeignKey to Company

class Product(Meta):
 company = models.ForeignKey(
 Company, 
 related_name='products', 
 on_delete=models.CASCADE
 )

I do the following filtering:

 company = Company.objects.filter(account=account, pk=company_pk)
 if not company:
 raise Http404
 product = Product.objects.filter(company=company, pk=product_pk)
 if not product:
 raise Http404
 return product

And I have the following error:

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

company_pk and product_pk are just variables. If I remove the Product filter there is no error.

I presume it happens because company result is a QuerySet and is pushed as argument in Product.objects.filter

Company is a queryset. You might want to do

Product.objects.filter(company=company[0], pk=product_pk)

Or better yet you can use the relations in the ORM to simplify into 1 lookup.

Product.objects.get(company__account=account, company__pk=company_pk, pk=product_pk) 

As said in the accepted answer, company is a queryset.

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

Instead of this

product = Product.objects.filter(company=company, pk=product_pk)

try this

product = Product.objects.filter(company__in=company, pk=product_pk)

__in can handle querysets larger than one (multiple records of a table).

This can be found in the django Many-to_one relationships section of the documentation.
https://docs.djangoproject.com/en/2.0/topics/db/examples/many_to_one/

Django documentation can be scary for a beginner like me because of its length and depth, though it provides solutions to most issues if you can crack it.

This error can also be created when you pass a queryset for the value you are searching with.

Company.objects.filter(account=account, pk=company_pk) actually returns a queryset and that queryset can't be used in this query Product.objects.filter(company=company, pk=product_pk) without producing the error message.

What is really missing here is a .get, either like

company = Company.objects.filter(account=account, pk=company_pk).get()
or company = Company.objects.get(account=account, pk=company_pk)