Develop Reference

Wagtail Page model transitive search on custom fields [duplicate]

I'm using Wagtail, and I want to filter a selection of child pages by a Foreign Key. I've tried the following and I get the error django.core.exceptions.FieldError: Cannot resolve keyword 'use_case' into field when I try children = self.get_children().specific().filter(use_case__slug=slug):
class AiLabResourceMixin(models.Model):
parent_page_types = ['AiLabResourceIndexPage']
use_case = models.ForeignKey(AiLabUseCase, on_delete=models.PROTECT)
content_panels = ArticlePage.content_panels + [
FieldPanel('use_case', widget=forms.Select())
]
class Meta:
abstract = True
class AiLabCaseStudy(AiLabResourceMixin, ArticlePage):
pass
class AiLabBlogPost(AiLabResourceMixin, ArticlePage):
pass
class AiLabExternalLink(AiLabResourceMixin, ArticlePage):
pass
class AiLabResourceIndexPage(RoutablePageMixin, BasePage):
parent_page_types = ['AiLabHomePage']
subpage_types = ['AiLabCaseStudy', 'AiLabBlogPost', 'AiLabExternalLink']
max_count = 1
#route(r'^$')
def all_resources(self, request):
children = self.get_children().specific()
return render(request, 'ai_lab/ai_lab_resource_index_page.html', {
'page': self,
'children': children,
})
#route(r'^([a-z0-9]+(?:-[a-z0-9]+)*)/$')
def filter_by_use_case(self, request, slug):
children = self.get_children().specific().filter(use_case__slug=slug)
return render(request, 'ai_lab/ai_lab_resource_index_page.html', {
'page': self,
'children': children,
})
I've seen this answer, but this assumes I only have one type of page I want to filter. Using something like AiLabCaseStudy.objects.filter(use_case__slug=slug) works, but this only returns AiLabCaseStudys, not AiLabBlogPosts or AiLabExternalLinks.
Any ideas?

At the database level, there is no efficient way to run the filter against all page types at once. Since AiLabResourceMixin is defined as abstract = True, this class has no representation of its own within the database - instead, the use_case field is defined separately for each of AiLabCaseStudy, AiLabBlogPost and AiLabExternalLink. As a result, there's no way for Django or Wagtail to turn .filter(use_case__slug=slug) into a SQL query, since use_case refers to three different places in the database.
A couple of possible ways around this:
If your data model allows, restructure it to use multi-table inheritance - this looks fairly similar to your current definition, except without the abstract = True:
class AiLabResourcePage(ArticlePage):
use_case = models.ForeignKey(AiLabUseCase, on_delete=models.PROTECT)
class AiLabCaseStudy(AiLabResourcePage):
pass
class AiLabBlogPost(AiLabResourcePage):
pass
class AiLabExternalLink(AiLabResourcePage):
pass
AiLabResourcePage will then exist in its own right in the database, and you can query its use_case field with an expression like: AiLabResourcePage.objects.child_of(self).filter(use_case__slug=slug).specific(). There'll be a small performance impact here, since Django has to pull data from one additional table to construct these page objects.
Run a preliminary query on each specific page type to retrieve the matching page IDs, before running the final query with specific():
case_study_ids = list(AiLabCaseStudy.objects.child_of(self).filter(use_case__slug=slug).values_list('id', flat=True))
blog_post_ids = list(AiLabBlogPost.objects.child_of(self).filter(use_case__slug=slug).values_list('id', flat=True))
external_link_ids = list(AiLabExternalLink.objects.child_of(self).filter(use_case__slug=slug).values_list('id', flat=True))
children = Page.objects.filter(id__in=(case_study_ids + blog_post_ids + external_link_ids)).specific()

Try:
children = self.get_children().filter(use_case__slug=slug).specific()

Django - Add object in front of existing QuerySet

I am building a library Django application where I have a BooksView to display all Books written by a certain Author. Under certain conditions, I want a single Book to be displayed before all other books in the query set. This should happen when the id of the book appears in the URL, otherwise, all books should be listed in chronological order.
books/urls.py:
urlpatterns = [
# Books displayed in chronological order
path("<slug:author>/books", views.BooksView.as_view()),
# Books displayed in chronological order
# but first book is the one with id `book`
path("<slug:author>/books/<int:book>", views.BooksView.as_view()),
]
books/views.py:
class BooksView(APIView):
def get(self, request, author, book=None):
author = get_object_or_404(Author, slug=author)
books = author.author_books
books = books.order_by("-pub_date")
if book:
book = get_object_or_404(Book, id=book)
# TODO: add `book` in front of books QuerySet (and remove duplicated if any)
serializer = BooksSerializer(books, many=True)
return Response(serializer.data)
How can I accomplish my TODO? How can I push an object in front of an existing query set?

This doesn't precisely answer your question but I think it would allow you to get the desired outcome: don't worry about preserving the queryset and instead transform it into a list.
This isn't a thing you want to do for every queryset in your entire codebase especially if it's a queryset that you might later want to build upon and compose with other filters, excludes, etc. But when you're about to render a page (like you are here) it is OK because you're about to cause the queryset to be evaluated anyhow. You're causing it to happen perhaps microseconds sooner.
class BooksView(APIView):
def get(self, request, author, book=None):
author = get_object_or_404(Author, slug=author)
books = list(author.author_books)
if book:
book = Book.objects.get(id=book)
# TODO: add `book` in front of books QuerySet (and remove duplicated if any)
books = [x for x in books if not x == book] # first remove if dup
books.insert(0, book) # now insert at front
serializer = BooksSerializer(books, many=True)
return Response(serializer.data)
EDIT 1
The BooksSerializer (which subclasses the BaseSerializer I suspect) is going to make a list anyhow as soon as you call it:
def to_representation(self, data):
"""
List of object instances -> List of dicts of primitive datatypes.
"""
# Dealing with nested relationships, data can be a Manager,
# so, first get a queryset from the Manager if needed
iterable = data.all() if isinstance(data, models.Manager) else data
return [
self.child.to_representation(item) for item in iterable
]
https://github.com/encode/django-rest-framework/blob/master/rest_framework/serializers.py#L663
EDIT 2
What about trying this instead? By adding the exclude before the queryset is evaluated into a list you prevent the O(n) scan through the list to find and remove the "main" book that's supposed to be at the top.
class BooksView(APIView):
def get(self, request, author, book=None):
author = get_object_or_404(Author, slug=author)
books = author.author_books
if book:
book = Book.objects.get(id=book)
# TODO: add `book` in front of books QuerySet (and remove duplicated if any)
# ensure the queryset doesn't include the "main" book
books = books.exclude(book_id=book.id)
# evaluate it into a list just like the BookSerializer will anyhow
books = list(books)
# now insert the "main" book at the front of the list
books.insert(0, book)
serializer = BooksSerializer(books, many=True)
return Response(serializer.data)

You can use the bitwise | operator as
from django.http.response import Http404
class BooksView(APIView):
def get(self, request, author, book=None):
author = get_object_or_404(Author, slug=author)
book_qs = author.author_books
if book:
single_book_qs = Book.objects.filter(id=book)
if not single_book_qs.exists():
raise Http404
book_qs = single_book_qs | book_qs
serializer = BooksSerializer(book_qs, many=True)
return Response(serializer.data)
Please note that one caveat of this solution is that, if you use the order_by(...) method, the position will be changed according to the ORDER By expression.
Update 1
Since you are using an order_by(...) expression, you must do something like this,
class BooksView(APIView):
def get(self, request, author, book=None):
author = get_object_or_404(Author, slug=author)
book_qs = author.author_books.order_by("-pub_date")
serialized_single_book = []
if book:
single_book = get_object_or_404(Book, id=book)
book_qs.exclude(id=book) # to remove dups
serialized_single_book = [BooksSerializer(single_book).data]
serializer = BooksSerializer(book_qs, many=True)
serialized_book_qs = serializer.data
return Response([*serialized_single_book, *serialized_book_qs])

This should do it, just use the union method in the QuerySet object, and exclude
the book we are trying to access from books queryset.
I did some minor changes to the code, but you don't need to do more than that, to accomplish what you need.
class BooksView(APIView):
def get(self, request, author, book=None):
author = get_object_or_404(Author, slug=author)
books = author.author_books.all().order_by('-pub_date')
if book:
# I am assuming this line if for validating that the request is valid.
# I've changed the query to also include author's slug,
# so the request doesn't get books not related to the author.
book_obj = get_object_or_404(Book, id=book, author__slug=author)
# Just Query the same book, and union it with the books queryset,
# excluding the current book in the book_obj
books = Book.objects.filter(id=book_obj.id).union(books.exclude(id=book_obj.id))
serializer = BooksSerializer(books, many=True)
return Response(serializer.data)

A little out of the box maybe, but if you want to keep it as queryset, then this is the solution. Please note that this solves the X problem, not the Y problem. The goal is to put one book first in the list, which can be achieved by insertion, but also by reordering based on an annotation.
from django.db.models import Case, When, Value, IntegerField
from rest_framework import generics
from . import models, serializers
class BooksPerAuthor(generics.ListAPIView):
serializer_class = serializers.BookWithoutAuthor
def get_queryset(self):
book_pk = self.kwargs.get("book", 0)
queryset = (
models.Book.objects.filter(author__slug=self.kwargs["author"])
.annotate(
promoted=Case(
When(pk=book_pk, then=Value(1)),
default=Value(0),
output_field=IntegerField(),
)
)
.order_by("-promoted", "-pub_date")
)
return queryset
This doesn't catch non-existing references - not a fan of returning 404 for list views and in case the promoted book is not in the collection, then there's no real harm done. Plenty of examples above to do the same thing with 404's at the (minor) cost of additional queries.

Foreign Key Resource from dynamic field

I've got an API endpoint called TrackMinResource, which returns the minimal data for a music track, including the track's main artist returned as an ArtistMinResource. Here are the definitions for both:
class TrackMinResource(ModelResource):
artist = fields.ForeignKey(ArtistMinResource, 'artist', full=True)
class Meta:
queryset = Track.objects.all()
resource_name = 'track-min'
fields = ['id', 'artist', 'track_name', 'label', 'release_year', 'release_name']
include_resource_uri = False
cache = SimpleCache(public=True)
def dehydrate(self, bundle):
bundle.data['full_artist_name'] = bundle.obj.full_artist_name()
if bundle.obj.image_url != settings.NO_TRACK_IMAGE:
bundle.data['image_url'] = bundle.obj.image_url
class ArtistMinResource(ModelResource):
class Meta:
queryset = Artist.objects.all()
resource_name = 'artist-min'
fields = ['id', 'artist_name']
cache = SimpleCache(public=True)
def get_resource_uri(self, bundle_or_obj):
return '/api/v1/artist/' + str(bundle_or_obj.obj.id) + '/'
The problem is, the artist field on Track (previously a ForeignKey) is now a model method called main_artist (I've changed the structure of the database somewhat, but I'd like the API to return the same data as it did before). Because of this, I get this error:
{"error": "The model '<Track: TrackName>' has an empty attribute 'artist' and doesn't allow a null value."}
If I take out full=True from the 'artist' field of TrackMinResource and add null=True instead, I get null values for the artist field in the returned data. If I then assign the artist in dehydrate like this:
bundle.data['artist'] = bundle.obj.main_artist()
...I just get the artist name in the returned JSON, rather than a dict representing an ArtistMinResource (along with the associated resource_uris, which I need).
Any idea how to get these ArtistMinResources into my TrackMinResource? I can access an ArtistMinResource that comes out fine using the URL endpoint and asking for it by ID. Is there a function for getting that result from within the dehydrate function for TrackMinResource?

You can use your ArtistMinResource in TrackMinResource's dehydrate like this (assuming that main_artist() returns the object that your ArtistMinResource represents):
artist_resource = ArtistMinResource()
artist_bundle = artist_resource.build_bundle(obj=bundle.obj.main_artist(), request=request)
artist_bundle = artist_resource.full_dehydrate(artist_bundle)
artist_json = artist_resource.serialize(request=request, data=artist_bundle, format='application/json')
artist_json should now contain your full artist representation. Also, I'm pretty sure you don't have to pass the format if you pass the request and it has a content-type header populated.

Django MultipleChoiceField choices of users throws error

I am trying to write a form that allows the user to select as many users from a specific group as they want. However when I try to use the list of users as an option I get an error saying that 'User' object does not support indexing.
Its a fairly standard form, the main difference is that the group is filtered based on a kwarg passed to the form. The form is passed a project_id (project object primary key) and it then finds the group associated with that project and generates the field.
From forms.py
class ModifyTeamForm(forms.Form):
action = ChoiceField(choices=[('remove', 'Remove users'), ('promote', 'Promote to lead.')])
def __init__(self, *args, **kwargs):
# The project to get the team for
project_id = kwargs.pop('project_id', None)
super(ModifyTeamForm, self).__init__(*args, **kwargs)
project = Project.objects.get(pk=project_id)
# Team for this project
team = User.objects.filter(groups__name=project.project_name)
# Create a form field to select current team members
current_team = MultipleChoiceField(required=True, choices = team, widget=CheckboxSelectMultiple)
# Add the field
self.fields['current_team'] = current_team
My views.py
#login_required
def team(request, project_id):
if request.method == "POST":
# Not yet implemented
return
else:
form = ModifyTeamForm(project_id=project_id)
template = loader.get_template('projects/team.html')
context = RequestContext(request, {
'form': form,
})
return HttpResponse(template.render(context))

It's because MultipleChoiceField.choices is expected to be a 2d Array effectively (https://docs.djangoproject.com/en/1.7/ref/forms/fields/#django.forms.ChoiceField.choices).
So you could do something like this:
team = [(u.pk, u.email) for u in User.objects.filter(groups__name=project.project_name)]
And that will return you a list continaing the combintation of
[('user1.pk', 'user1.email'), ('user2.pk', 'user2.email'),...]
which will be useable as the choices.

How to override createView to save multiple data entry

using CreateView class, I want to save multiple data entries.
example inputs:
item is "apple,banana,carrots"
location is "location 1"
I want to save them to database like this:
[apple, location 1]
[banana, location 1]
[carrots, location 1]
#model.py
class Inventory(models.Model):
item = models.CharField(max_length=14)
location = models.CharField(max_length=10)
#forms.py
class InventoryCreateForm(forms.ModelForm):
item = forms.CharField(widget=forms.Textarea(attrs={'rows': 8,
'cols': 14}))
class Meta:
model = Inventory
#views.py
class InventoryCreateView(CreateView):
model = Inventory
form_class = InventoryCreateForm
Thank you

You need to override the "form_valid()" method used by the createview.
You then need to read in the form data
def form_valid(self,form):
self.object = form.save(commit=False)
foo = self.object.bar #your data is in the object
Then because you are using a textfield you need to somehow split the data passed into the form and loop over those values. Ideally you will want a list of items ['apple', 'banana', 'pear']
then take the location out of the list and store that into a variable that can be used later on location_variable.
Once you have the data in the form you want you then need to instantiate the Inventory model
from foo.models import Inventory #import at the top of your file
for item is list:
inventory = Inventory()
inventory.item = item
inventory.location = location_variable
inventory.save()
I hope this answer can help you in some way, if you would like further details on Class based view, visit ccbv where all of the information for each view is listed.
Otherwise you can look in the django Form docs for a more suitable form to use.

hopefully this helps anyone else who comes to this page.
Here is what I did:
class TrainingBulkCreateForm(ModelForm):
# todo: could we make the original user object a multiple choice field instead?
extra_user = forms.ModelMultipleChoiceField(queryset=User.objects.filter(is_active=True), required=True)
class Meta(object):
model = Training
fields = '__all__'
def post(self, request, *args, **kwargs):
result = super().post(request, *args, **kwargs)
users = request.POST.getlist('extra_user')
if users:
# modify request.POST data then re-save the additional users
for user in users:
# Need to copy the data because the initial QueryDict is immutable data
postdata_copy = request.POST.copy()
postdata_copy['user'] = user
form2 = TrainingBulkCreateForm(postdata_copy)
form2.save()
return result
I have my item field (mine is user) split into two form fields - the original item which is 1 object like apple.
Then I also have extra_user as a second form field. This takes multiple objects like [banana, carrots]
In the view I invoke the super().post(...) to save the initial apple object.
Then I check for the extra_user field to see if there are multiple foods. If there are extras, I copy the immutable QueryDict object request.POST as postdata_copy.
Then I modify postdata_copy so instead of having apple we replace with banana. (This basically just duplicates the apple form into a new copy with banana and re-saves the form). Then we loop again and replace apple with carrots.
Note that my Form object uses ModelMultipleChoiceField for extra_user object. This has better data integrity than typing in raw text.