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Django 4.0 release notes - UNDER DEVELOPMENT

Expected December 2021

Welcome to Django 4.0!

These release notes cover the new features, as well as some backwards incompatible changes you’ll want to be aware of when upgrading from Django 3.2 or earlier. We’ve begun the deprecation process for some features.

See the Upgrading Django to a newer version guide if you’re updating an existing project.

Python compatibility

Django 4.0 supports Python 3.8, 3.9, and 3.10. We highly recommend and only officially support the latest release of each series.

The Django 3.2.x series is the last to support Python 3.6 and 3.7.

What’s new in Django 4.0

Functional unique constraints

The new *expressions positional argument of UniqueConstraint() enables creating functional unique constraints on expressions and database functions. For example:

from django.db import models
from django.db.models import UniqueConstraint
from django.db.models.functions import Lower


class MyModel(models.Model):
    first_name = models.CharField(max_length=255)
    last_name = models.CharField(max_length=255)

    class Meta:
        indexes = [
            UniqueConstraint(
                Lower('first_name'),
                Lower('last_name').desc(),
                name='first_last_name_unique',
            ),
        ]

Functional unique constraints are added to models using the Meta.constraints option.

Minor features

django.contrib.admin

  • The admin/base.html template now has a new block header which contains the admin site header.
  • The new ModelAdmin.get_formset_kwargs() method allows customizing the keyword arguments passed to the constructor of a formset.

django.contrib.admindocs

  • The admindocs now allows esoteric setups where ROOT_URLCONF is not a string.
  • The model section of the admindocs now shows cached properties.

django.contrib.auth

django.contrib.postgres

Cache

CSRF

Decorators

Email

Error Reporting

File Storage

File Uploads

Forms

  • ModelChoiceField now includes the provided value in the params argument of a raised ValidationError for the invalid_choice error message. This allows custom error messages to use the %(value)s placeholder.

Generic Views

Internationalization

Logging

Management Commands

Migrations

Models

Requests and Responses

Security

Serialization

Signals

  • The new stdout argument for pre_migrate() and post_migrate() signals allows redirecting output to a stream-like object. It should be preferred over sys.stdout and print() when emitting verbose output in order to allow proper capture when testing.

Templates

Tests

URLs

Utilities

Validators

Backwards incompatible changes in 4.0

Database backend API

This section describes changes that may be needed in third-party database backends.

django.contrib.gis

  • Support for PostGIS 2.3 is removed.

Dropped support for PostgreSQL 9.6

Upstream support for PostgreSQL 9.6 ends in November 2021. Django 4.0 supports PostgreSQL 10 and higher.

Dropped support for Oracle 12.2 and 18c

Upstream support for Oracle 12.2 ends in March 2022 and for Oracle 18c it ends in June 2021. Django 3.2 will be supported until April 2024. Django 4.0 officially supports Oracle 19c.

Miscellaneous

  • Support for cx_Oracle < 7.0 is removed.
  • To allow serving a Django site on a subpath without changing the value of STATIC_URL, the leading slash is removed from that setting (now 'static/') in the default startproject template.

Features deprecated in 4.0

Miscellaneous

Features removed in 4.0

These features have reached the end of their deprecation cycle and are removed in Django 4.0.

See Features deprecated in 3.0 for details on these changes, including how to remove usage of these features.

  • django.utils.http.urlquote(), urlquote_plus(), urlunquote(), and urlunquote_plus() are removed.
  • django.utils.encoding.force_text() and smart_text() are removed.
  • django.utils.translation.ugettext(), ugettext_lazy(), ugettext_noop(), ungettext(), and ungettext_lazy() are removed.
  • django.views.i18n.set_language() doesn’t set the user language in request.session (key _language).
  • alias=None is required in the signature of django.db.models.Expression.get_group_by_cols() subclasses.
  • django.utils.text.unescape_entities() is removed.
  • django.utils.http.is_safe_url() is removed.

See Features deprecated in 3.1 for details on these changes, including how to remove usage of these features.

  • The PASSWORD_RESET_TIMEOUT_DAYS setting is removed.
  • The isnull lookup no longer allows using non-boolean values as the right-hand side.
  • The django.db.models.query_utils.InvalidQuery exception class is removed.
  • The django-admin.py entry point is removed.
  • The HttpRequest.is_ajax() method is removed.
  • Support for the pre-Django 3.1 encoding format of cookies values used by django.contrib.messages.storage.cookie.CookieStorage is removed.
  • Support for the pre-Django 3.1 password reset tokens in the admin site (that use the SHA-1 hashing algorithm) is removed.
  • Support for the pre-Django 3.1 encoding format of sessions is removed.
  • Support for the pre-Django 3.1 django.core.signing.Signer signatures (encoded with the SHA-1 algorithm) is removed.
  • Support for the pre-Django 3.1 django.core.signing.dumps() signatures (encoded with the SHA-1 algorithm) in django.core.signing.loads() is removed.
  • Support for the pre-Django 3.1 user sessions (that use the SHA-1 algorithm) is removed.
  • The get_request argument for django.utils.deprecation.MiddlewareMixin.__init__() is required and doesn’t accept None.
  • The providing_args argument for django.dispatch.Signal is removed.
  • The length argument for django.utils.crypto.get_random_string() is required.
  • The list message for ModelMultipleChoiceField is removed.
  • Support for passing raw column aliases to QuerySet.order_by() is removed.
  • The NullBooleanField model field is removed, except for support in historical migrations.
  • django.conf.urls.url() is removed.
  • The django.contrib.postgres.fields.JSONField model field is removed, except for support in historical migrations.
  • django.contrib.postgres.fields.jsonb.KeyTransform and django.contrib.postgres.fields.jsonb.KeyTextTransform are removed.
  • django.contrib.postgres.forms.JSONField is removed.
  • The {% ifequal %} and {% ifnotequal %} template tags are removed.
  • The DEFAULT_HASHING_ALGORITHM transitional setting is removed.
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