Django __in queryset

__in is a commonly used lookup in Django's QuerySet API. It is used to filter results based on whether or not a particular value is contained within a list or a queryset.

Usage

The __in lookup is used to filter a QuerySet based on whether or not a particular value is contained within a specified list or a queryset.

Filter by list of values

from myapp.models import MyModel

values = [1, 2, 3, 4]
queryset = MyModel.objects.filter(id__in=values)

This will return a QuerySet containing only instances of MyModel whose id attribute is in the specified list of values.

Filter by queryset

from myapp.models import MyModel

related_queryset = OtherModel.objects.filter(name='foo')
queryset = MyModel.objects.filter(other_model__in=related_query)

This will return a QuerySet containing only instances of MyModel that have a related OtherModel instance with a name attribute of 'foo'.

Conclusion

The __in lookup is a powerful tool for filtering QuerySets based on the contents of either a list or another queryset. It is a useful technique to have in your toolbox when working with Django's ORM.