Topic guide Pagination

Under the hood, all methods of pagination use the Paginator class. It does all the heavy lifting of actually splitting a QuerySet into Page objects.

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Topic guide Pagination

Here’s an example using Paginator in a view function to paginate a queryset: In the template list.html, you can include navigation between pages in the same way as in the template for the ListView above.

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Topic guide Performance and optimization

Django is itself quite lazy. A good example of this can be found in the evaluation of a QuerySet. QuerySets are lazy.

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Topic guide Security in Django

This can result in records being deleted or data leakage. Django’s querysets are protected from SQL injection since their queries are constructed using query parameterization. A query’s SQL code is defined separately from the query’s parameters.

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Topic guide Serializing Django objects

At the highest level, you can serialize data like this: The arguments to the serialize function are the format to serialize the data to (see Serialization formats) and a QuerySet to serialize.

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Tutorial Writing your first Django app, part 3 Raising a 404 error

It’s a very common idiom to use get() and raise Http404 if the object doesn’t exist. Django provides a shortcut.

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Design philosophies Database API

This is also why the select_related() QuerySet method exists. It’s an optional performance booster for the common case of selecting “every related object.”

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Reference Generic display views

classdjango.views.generic.list.ListView : A page representing a list of objects. classdjango.views.generic.list.BaseListView : A base view for displaying a list of objects.

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Reference Date-based mixins

classDateMixin[source] : A mixin class providing common behavior for all date-based views.

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Reference Single object mixins

classdjango.views.generic.detail.SingleObjectMixin : Provides a mechanism for looking up an object associated with the current HTTP request.

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Reference Admin actions Advanced action techniques

Actions may limit their availability to users with specific permissions by wrapping the action function with the action() decorator and passing the permissions argument: The make_published() action will only be available to users that pass the ModelAdmin.has_change_permission() check.

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Reference ModelAdmin List Filters

… own list filter by subclassing django.contrib.admin.SimpleListFilter. You need to provide the title and parameter_name attributes, and override the lookups and queryset methods, e.g.: NOTE: As a convenience, the HttpRequest object is passed to the lookups > and queryset methods, for …

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Reference The Django admin site ModelAdmin objects

ModelAdmin.formfield_for_manytomany(db_field,request,**kwargs) : Like the formfield_for_foreignkey method, the formfield_for_manytomany method can be overridden to change the default formfield for a many to many field.

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Reference django.contrib.auth Authentication backends

[`with_perm()`](#django.contrib.auth.backends.ModelBackend.with_perm) also allows an object to be passed as a parameter, but unlike other methods it returns an empty queryset if `obj is not None`. `authenticate(request,username=None,password=None,**kwargs)`[[source]](https://github.com/django/django/blob/stable/6.0.x/django/contrib/auth/backends.py#L59) `aauthenticate(request,username=None,password=None,**kwargs)` : *Asynchronous version*: `aauthenticate()` Tries to authenticate `username` with `password` by calling [`User.check_password`](#django.contrib.auth.models.User.check_password).

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Reference Geographic Database Functions Measurements

classGeometryDistance(expr1,expr2,**extra)[source] Availability: PostGIS Accepts two geographic fields or expressions and returns the distance between them. When used in an order_by() clause, it provides index-assisted nearest-neighbor result sets.

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Reference The sitemap framework

The sitemap framework provides a convenience class for a common case: classGenericSitemap(info_dict,priority=None,changefreq=None,protocol=None)[source] : The django.contrib.sitemaps.GenericSitemap class allows you to create a sitemap by passing it a dictionary which has to contain at least a queryset entry.

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Reference The sitemap framework Shortcuts

Here’s an example of a URLconf using GenericSitemap:

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Reference Django Exceptions Django Core Exceptions

exceptionObjectDoesNotExist[source] : The base class for Model.DoesNotExist exceptions. A try/except for ObjectDoesNotExist will catch DoesNotExist exceptions for all models.

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Reference Django Exceptions Django Core Exceptions

exceptionMultipleObjectsReturned[source] : The base class for Model.MultipleObjectsReturned exceptions. A try/except for MultipleObjectsReturned will catch MultipleObjectsReturned exceptions for all models.

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Reference Form fields

Two fields are available for representing relationships between models: ModelChoiceField and ModelMultipleChoiceField. Both of these fields require a single queryset parameter that is used to create the choices for the field.

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