How to apply filter on django ManyToManyField so that multiple value of the field follow the condition?

Question

class Publication(models.Model):
    title = models.CharField(max_length=30)


class Article(models.Model):
    headline = models.CharField(max_length=100)
    publications = models.ManyToManyField(Publication)

p1 = Publication.objects.create(title='The Python Journal')
p2 = Publication.objects.create(title='Science News')
p3 = Publication.objects.create(title='Science Weekly')

I want to filter articles, published in both p1 and p3. They might or might not publish in other publications but they must have to publish in p1 and p3.

I have tried:

Article.objects.filter(Q(publications=p1) & Q(publications=p3))

but it returns empty queryset which is not true

Asked By: Tanvir Ahmed

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Source

Answer 1

There are many examples of FOO__in=... style filters in the many-to-many and many-to-one tests. Here is syntax for your specific problem:

# filtering on a few publications, by id
articles = Article.objects.filter(publications__in=[<id1>, <id2>, <id3>])
# and by publication object (object gets converted to pk under the covers)
articles = Article.objects.filter(publications__in=[publication1, publication2, publication3])
# and by publication title
articles = Article.objects.filter(publications__title__icontains='Science')

The icontains used to i for case-insensitive, contains for that the word contains those letters and maybe there are fewer or more letters.

The double underscore (__) syntax is used all over the place when working with queryset.

Answered By: Ashrof

Answer 2

If you chain mutliple calls to filter() they should behave like being connected with an AND:

articles = Article.objects.filter(publications=p1).filter(publications=p3).distinct()

Answered By: Bernhard Vallant

Answer 3

I had a similar problem where some users ended with a free role and also a paid role, so I needed to select users that have two specific roles on the many to many field.

I did something like this, works like a charm

roles = [premium_role, default_role]

DiscordUser.objects.filter(guild=guild)
    .annotate(freemium=Count('roles', filter=Q(roles__in=roles)))
    .filter(freemium=2)
    .values('id')

Answered By: giosan

How to apply filter on django ManyToManyField so that multiple value of the field follow the condition?

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