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adding additional django examples
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‎content/pages/examples/django/django-db-models-query-baseiterable.markdown‎

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title: django.db.models.query BaseIterable Example Code
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category: page
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slug: django-db-models-query-baseiterable-examples
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sortorder: 500011238
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toc: False
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sidebartitle: django.db.models.query BaseIterable
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meta: Python example code for the BaseIterable class from the django.db.models.query module of the Django project.
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BaseIterable is a class within the django.db.models.query module of the Django project.
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## Example 1 from wagtail
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[wagtail](https://github.com/wagtail/wagtail)
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([project website](https://wagtail.io/)) is a fantastic
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[Django](/django.html)-based CMS with code that is open source
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under the
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[BSD 3-Clause "New" or "Revised" License](https://github.com/wagtail/wagtail/blob/master/LICENSE).
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[**wagtail / wagtail / core / query.py**](https://github.com/wagtail/wagtail/blob/master/wagtail/core/query.py)
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```python
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# query.py
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import posixpath
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import warnings
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from collections import defaultdict
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from django.apps import apps
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from django.contrib.contenttypes.models import ContentType
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from django.db.models import CharField, Q
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from django.db.models.functions import Length, Substr
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~~from django.db.models.query import BaseIterable
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from treebeard.mp_tree import MP_NodeQuerySet
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from wagtail.search.queryset import SearchableQuerySetMixin
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class TreeQuerySet(MP_NodeQuerySet):
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def delete(self):
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super().delete()
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delete.queryset_only = True
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def descendant_of_q(self, other, inclusive=False):
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q = Q(path__startswith=other.path) & Q(depth__gte=other.depth)
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if not inclusive:
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q &= -Q(pk=other.pk)
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return q
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def descendant_of(self, other, inclusive=False):
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return self.filter(self.descendant_of_q(other, inclusive))
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def not_descendant_of(self, other, inclusive=False):
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return self.exclude(self.descendant_of_q(other, inclusive))
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## ... source file abbreviated to get to BaseIterable examples ...
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if missing_pks:
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generic_pages = Page.objects.filter(pk__in=missing_pks).select_related('content_type').in_bulk()
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warnings.warn(
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"Specific versions of the following pages could not be found. "
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"This is most likely because a database migration has removed "
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"the relevant table or record since the page was created:\n{}".format([
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{'id': p.id, 'title': p.title, 'type': p.content_type}
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for p in generic_pages.values()
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]), category=RuntimeWarning
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)
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else:
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generic_pages = {}
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for pk, content_type in pks_and_types:
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try:
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page = pages_by_type[content_type][pk]
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except KeyError:
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page = generic_pages[pk]
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if annotation_aliases:
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for annotation, value in annotations_by_pk.get(page.pk, {}).items():
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setattr(page, annotation, value)
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yield page
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~~class SpecificIterable(BaseIterable):
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def __iter__(self):
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return specific_iterator(self.queryset)
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~~class DeferredSpecificIterable(BaseIterable):
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def __iter__(self):
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return specific_iterator(self.queryset, defer=True)
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## ... source file continues with no further BaseIterable examples...
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```
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‎content/pages/examples/django/django-db-models-query-emptyqueryset.markdown‎

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title: django.db.models.query EmptyQuerySet Example Code
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category: page
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slug: django-db-models-query-emptyqueryset-examples
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sortorder: 500011239
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toc: False
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sidebartitle: django.db.models.query EmptyQuerySet
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meta: Python example code for the EmptyQuerySet class from the django.db.models.query module of the Django project.
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EmptyQuerySet is a class within the django.db.models.query module of the Django project.
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## Example 1 from django-wiki
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[django-wiki](https://github.com/django-wiki/django-wiki)
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([project documentation](https://django-wiki.readthedocs.io/en/master/),
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[demo](https://demo.django-wiki.org/),
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and [PyPI page](https://pypi.org/project/django-wiki/))
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is a wiki system code library for [Django](/django.html)
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projects that makes it easier to create user-editable content.
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The project aims to provide necessary core features and then
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have an easy plugin format for additional features, rather than
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having every exhaustive feature built into the core system.
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django-wiki is a rewrite of an earlier now-defunct project
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named [django-simplewiki](https://code.google.com/p/django-simple-wiki/).
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The code for django-wiki is provided as open source under the
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[GNU General Public License 3.0](https://github.com/django-wiki/django-wiki/blob/master/COPYING).
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[**django-wiki / src/wiki / managers.py**](https://github.com/django-wiki/django-wiki/blob/master/src/wiki/./managers.py)
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```python
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# managers.py
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from django.db import models
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from django.db.models import Count
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from django.db.models import Q
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~~from django.db.models.query import EmptyQuerySet
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from django.db.models.query import QuerySet
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from mptt.managers import TreeManager
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class ArticleQuerySet(QuerySet):
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def can_read(self, user):
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if user.has_perm("wiki.moderator"):
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return self
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if user.is_anonymous:
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q = self.filter(other_read=True)
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else:
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q = self.filter(
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Q(other_read=True)
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| Q(owner=user)
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| (Q(group__user=user) & Q(group_read=True))
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).annotate(Count("id"))
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return q
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def can_write(self, user):
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if user.has_perm("wiki.moderator"):
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return self
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if user.is_anonymous:
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q = self.filter(other_write=True)
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else:
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q = self.filter(
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Q(other_write=True)
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| Q(owner=user)
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| (Q(group__user=user) & Q(group_write=True))
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)
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return q
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def active(self):
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return self.filter(current_revision__deleted=False)
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~~class ArticleEmptyQuerySet(EmptyQuerySet):
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def can_read(self, user):
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return self
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def can_write(self, user):
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return self
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def active(self):
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return self
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class ArticleFkQuerySetMixin:
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def can_read(self, user):
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if user.has_perm("wiki.moderate"):
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return self
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if user.is_anonymous:
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q = self.filter(article__other_read=True)
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else:
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q = self.filter(
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Q(article__other_read=True)
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| Q(article__owner=user)
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| (Q(article__group__user=user) & Q(article__group_read=True))
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).annotate(Count("id"))
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return q
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## ... source file abbreviated to get to EmptyQuerySet examples ...
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def can_read(self, user):
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return self.get_queryset().can_read(user)
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def can_write(self, user):
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return self.get_queryset().can_write(user)
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class ArticleFkManager(models.Manager):
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def get_empty_query_set(self):
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return self.get_queryset().none()
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def get_queryset(self):
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return ArticleFkQuerySet(self.model, using=self._db)
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def active(self):
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return self.get_queryset().active()
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def can_read(self, user):
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return self.get_queryset().can_read(user)
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def can_write(self, user):
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return self.get_queryset().can_write(user)
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~~class URLPathEmptyQuerySet(EmptyQuerySet, ArticleFkEmptyQuerySetMixin):
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def select_related_common(self):
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return self
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def default_order(self):
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return self
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class URLPathQuerySet(QuerySet, ArticleFkQuerySetMixin):
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def select_related_common(self):
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return self.select_related(
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"parent", "article__current_revision", "article__owner"
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)
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def default_order(self):
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return self.order_by("article__current_revision__title")
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class URLPathManager(TreeManager):
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def get_empty_query_set(self):
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return self.get_queryset().none()
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def get_queryset(self):
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return URLPathQuerySet(self.model, using=self._db).order_by(
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self.tree_id_attr, self.left_attr
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Q(article__other_write=True)
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| Q(article__owner=user)
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| (Q(article__group__user=user) & Q(article__group_write=True))
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).annotate(Count("id"))
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return q
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def active(self):
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return self.filter(article__current_revision__deleted=False)
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class ArticleFkEmptyQuerySetMixin:
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def can_read(self, user):
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return self
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def can_write(self, user):
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return self
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def active(self):
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return self
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class ArticleFkQuerySet(ArticleFkQuerySetMixin, QuerySet):
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pass
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~~class ArticleFkEmptyQuerySet(ArticleFkEmptyQuerySetMixin, EmptyQuerySet):
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pass
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class ArticleManager(models.Manager):
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def get_empty_query_set(self):
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return self.get_queryset().none()
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def get_queryset(self):
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return ArticleQuerySet(self.model, using=self._db)
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def active(self):
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return self.get_queryset().active()
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## ... source file continues with no further EmptyQuerySet examples...
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```
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‎content/pages/examples/django/django-db-models-query-modeliterable.markdown‎

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title: django.db.models.query ModelIterable Example Code
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category: page
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slug: django-db-models-query-modeliterable-examples
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sortorder: 500011240
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toc: False
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sidebartitle: django.db.models.query ModelIterable
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meta: Python example code for the ModelIterable class from the django.db.models.query module of the Django project.
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ModelIterable is a class within the django.db.models.query module of the Django project.
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## Example 1 from django-model-utils
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[django-model-utils](https://github.com/jazzband/django-model-utils)
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([project documentation](https://django-model-utils.readthedocs.io/en/latest/)
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and
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[PyPI package information](https://pypi.org/project/django-model-utils/))
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provides useful mixins and utilities for working with
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[Django ORM](/django-orm.html) models in your projects.
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The django-model-utils project is open sourced under the
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[BSD 3-Clause "New" or "Revised" License](https://github.com/jazzband/django-model-utils/blob/master/LICENSE.txt).
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[**django-model-utils / model_utils / managers.py**](https://github.com/jazzband/django-model-utils/blob/master/model_utils/./managers.py)
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```python
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# managers.py
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import django
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from django.core.exceptions import ObjectDoesNotExist
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from django.db import connection
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from django.db import models
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from django.db.models.constants import LOOKUP_SEP
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from django.db.models.fields.related import OneToOneField, OneToOneRel
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~~from django.db.models.query import ModelIterable
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from django.db.models.query import QuerySet
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from django.db.models.sql.datastructures import Join
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~~class InheritanceIterable(ModelIterable):
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def __iter__(self):
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queryset = self.queryset
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~~ iter = ModelIterable(queryset)
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if getattr(queryset, 'subclasses', False):
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extras = tuple(queryset.query.extra.keys())
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subclasses = sorted(queryset.subclasses, key=len, reverse=True)
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for obj in iter:
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sub_obj = None
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for s in subclasses:
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sub_obj = queryset._get_sub_obj_recurse(obj, s)
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if sub_obj:
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break
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if not sub_obj:
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sub_obj = obj
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if getattr(queryset, '_annotated', False):
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for k in queryset._annotated:
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setattr(sub_obj, k, getattr(obj, k))
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for k in extras:
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setattr(sub_obj, k, getattr(obj, k))
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yield sub_obj
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else:
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yield from iter
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## ... source file continues with no further ModelIterable examples...
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```
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