Django: change the value of a field for all objects in a queryset
You can update all the records in the queryset with qs.update(active=False) Please refer to the official Django documentation for more info
django-queryset
‘RelatedManager’ object is not iterable Django
Call all() to retrieve the elements from the manager. {% for area in world_areas.all %}
Django Query That Get Most Recent Objects From Different Categories
Starting from Django 1.11 and thanks to Subquery and OuterRef, we can finally build a latest-per-group query using the ORM. hottest_cakes = Cake.objects.filter( baked_at=Subquery( (Cake.objects .filter(bakery=OuterRef(‘bakery’)) .values(‘bakery’) .annotate(last_bake=Max(‘baked_at’)) .values(‘last_bake’)[:1] ) ) ) #BONUS, we can now use this for prefetch_related() bakeries = Bakery.objects.all().prefetch_related( Prefetch(‘cake_set’, queryset=hottest_cakes, to_attr=”hottest_cakes” ) ) #usage for bakery in bakeries: print ‘Bakery … Read more
Django query datetime for objects older than 5 hours
If Widget is the name of your model, and it has a DateTimeField attribute named created, the query would be: from datetime import datetime, timedelta time_threshold = datetime.now() – timedelta(hours=5) results = Widget.objects.filter(created__lt=time_threshold) Note that created__lt means “created is less than”.
Django filter the model on ManyToMany count?
If this works this is how I would do it. Best way can mean a lot of things: best performance, most maintainable, etc. Therefore I will not say this is the best way, but I like to stick to the ORM features as much as possible since it seems more maintainable. from django.db.models import Count … Read more
How to annotate Count with a condition in a Django queryset
For django >= 1.8 Use Conditional Aggregation: from django.db.models import Count, Case, When, IntegerField Article.objects.annotate( numviews=Count(Case( When(readership__what_time__lt=treshold, then=1), output_field=IntegerField(), )) ) Explanation: normal query through your articles will be annotated with numviews field. That field will be constructed as a CASE/WHEN expression, wrapped by Count, that will return 1 for readership matching criteria and NULL … Read more
Django Queryset with filtering on reverse foreign key
Yes, I think you want make = Make.objects.get(pk=1) make.make_content_set.filter(published=True) or maybe make_ids = MakeContent.objects.filter(published=True).values_list(‘make_id’, flat=True) makes = Make.objects.filter(id__in=make_ids)
How to get primary keys of objects created using django bulk_create
2016 Since Django 1.10 – it’s now supported (on Postgres only) here is a link to the doc. >>> list_of_objects = Entry.objects.bulk_create([ … Entry(headline=”Django 2.0 Released”), … Entry(headline=”Django 2.1 Announced”), … Entry(headline=”Breaking: Django is awesome”) … ]) >>> list_of_objects[0].id 1 From the change log: Changed in Django 1.10: Support for setting primary keys on objects … Read more
How to create a Django queryset filter comparing two date fields in the same model
F objects. from django.db.models import F stale_activities = Activity.objects.filter(updated__gte=F(‘added_toSolr_date’))
Why does django’s prefetch_related() only work with all() and not filter()?
In Django 1.6 and earlier, it is not possible to avoid the extra queries. The prefetch_related call effectively caches the results of a.photoset.all() for every album in the queryset. However, a.photoset.filter(format=1) is a different queryset, so you will generate an extra query for every album. This is explained in the prefetch_related docs. The filter(format=1) is … Read more