# documentación de Django - 5.1.7

# Django 3.0 release notes

December 2, 2019

Welcome to Django 3.0!

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 2.2 or earlier. We’ve dropped some features that have reached the end of their deprecation cycle, and we’ve begun the deprecation process for some features.

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

## Python compatibility

Django 3.0 supports Python 3.6, 3.7, 3.8, and 3.9 (as of 3.0.11). We highly recommend and only officially support the latest release of each series.

The Django 2.2.x series is the last to support Python 3.5.

## Third-party library support for older version of Django

Following the release of Django 3.0, we suggest that third-party app authors drop support for all versions of Django prior to 2.2. At that time, you should be able to run your package’s tests using `python -Wd` so that deprecation warnings appear. After making the deprecation warning fixes, your app should be compatible with Django 3.0.

## What’s new in Django 3.0

### MariaDB support

Django now officially supports MariaDB 10.1 and higher. See MariaDB notes for more details.

### ASGI support

Django 3.0 begins our journey to making Django fully async-capable by providing support for running as an ASGI application.

This is in addition to our existing WSGI support. Django intends to support both for the foreseeable future. Async features will only be available to applications that run under ASGI, however.

At this stage async support only applies to the outer ASGI application. Internally everything remains synchronous. Asynchronous middleware, views, etc. are not yet supported. You can, however, use ASGI middleware around Django’s application, allowing you to combine Django with other ASGI frameworks.

There is no need to switch your applications over unless you want to start experimenting with asynchronous code, but we have documentation on deploying with ASGI if you want to learn more.

Note that as a side-effect of this change, Django is now aware of asynchronous event loops and will block you calling code marked as «async unsafe» - such as ORM operations - from an asynchronous context. If you were using Django from async code before, this may trigger if you were doing it incorrectly. If you see a `SynchronousOnlyOperation` error, then closely examine your code and move any database operations to be in a synchronous child thread.

### Exclusion constraints on PostgreSQL

The new `ExclusionConstraint` class enable adding exclusion constraints on PostgreSQL. Constraints are added to models using the `Meta.constraints` option.

### Filter expressions

Expressions that output `BooleanField` may now be used directly in `QuerySet` filters, without having to first annotate and then filter against the annotation.

### Enumerations for model field choices

Custom enumeration types `TextChoices`, `IntegerChoices`, and `Choices` are now available as a way to define `Field.choices`. `TextChoices` and `IntegerChoices` types are provided for text and integer fields. The `Choices` class allows defining a compatible enumeration for other concrete data types. These custom enumeration types support human-readable labels that can be translated and accessed via a property on the enumeration or its members. See Enumeration types for more details and examples.

### Minor features

#### `django.contrib.admin`

- Added support for the `admin_order_field` attribute on properties in `ModelAdmin.list_display`.

- The new `ModelAdmin.get_inlines()` method allows specifying the inlines based on the request or model instance.

- Select2 library is upgraded from version 4.0.3 to 4.0.7.

- jQuery is upgraded from version 3.3.1 to 3.4.1.

#### `django.contrib.auth`

- The new `reset_url_token` attribute in `PasswordResetConfirmView` allows specifying a token parameter displayed as a component of password reset URLs.

- Added `BaseBackend` class to ease customization of authentication backends.

- Added `get_user_permissions()` method to mirror the existing `get_group_permissions()` method.

- Added HTML `autocomplete` attribute to widgets of username, email, and password fields in `django.contrib.auth.forms` for better interaction with browser password managers.

- `createsuperuser` now falls back to environment variables for password and required fields, when a corresponding command line argument isn’t provided in non-interactive mode.

- `REQUIRED_FIELDS` now supports `ManyToManyField`s.

- The new `UserManager.with_perm()` method returns users that have the specified permission.

- The default iteration count for the PBKDF2 password hasher is increased from 150,000 to 180,000.

#### `django.contrib.gis`

- Allowed MySQL spatial lookup functions to operate on real geometries. Previous support was limited to bounding boxes.

- Added the `GeometryDistance` function, supported on PostGIS.

- Added support for the `furlong` unit in `Distance`.

- The `GEOIP_PATH` setting now supports `pathlib.Path`.

- The `GeoIP2` class now accepts `pathlib.Path` `path`.

#### `django.contrib.postgres`

- The new `RangeOperators` helps to avoid typos in SQL operators that can be used together with `RangeField`.

- The new `RangeBoundary` expression represents the range boundaries.

- The new `AddIndexConcurrently` and `RemoveIndexConcurrently` classes allow creating and dropping indexes `CONCURRENTLY` on PostgreSQL.

#### `django.contrib.sessions`

- The new `get_session_cookie_age()` method allows dynamically specifying the session cookie age.

#### `django.contrib.syndication`

- Added the `language` class attribute to the `django.contrib.syndication.views.Feed` to customize a feed language. The default value is `get_language()` instead of `LANGUAGE_CODE`.

#### Cache

- `add_never_cache_headers()` and `never_cache()` now add the `private` directive to `Cache-Control` headers.

#### File Storage

- The new `Storage.get_alternative_name()` method allows customizing the algorithm for generating filenames if a file with the uploaded name already exists.

#### Forms

- Formsets may control the widget used when ordering forms via `can_order` by setting the `ordering_widget` attribute or overriding `get_ordering_widget()`.

#### Internationalization

- Added the `LANGUAGE_COOKIE_HTTPONLY`, `LANGUAGE_COOKIE_SAMESITE`, and `LANGUAGE_COOKIE_SECURE` settings to set the `HttpOnly`, `SameSite`, and `Secure` flags on language cookies. The default values of these settings preserve the previous behavior.

- Added support and translations for the Uzbek language.

#### Logging

- The new `reporter_class` parameter of `AdminEmailHandler` allows providing an `django.views.debug.ExceptionReporter` subclass to customize the traceback text sent to site `ADMINS` when `DEBUG` is `False`.

#### Management Commands

- The new `compilemessages --ignore` option allows ignoring specific directories when searching for `.po` files to compile.

- `showmigrations --list` now shows the applied datetimes when `--verbosity` is 2 and above.

- On PostgreSQL, `dbshell` now supports client-side TLS certificates.

- `inspectdb` now introspects `OneToOneField` when a foreign key has a unique or primary key constraint.

- The new `--skip-checks` option skips running system checks prior to running the command.

- The `startapp --template` and `startproject --template` options now support templates stored in XZ archives (`.tar.xz`, `.txz`) and LZMA archives (`.tar.lzma`, `.tlz`).

#### Models

- Added hash database functions `MD5`, `SHA1`, `SHA224`, `SHA256`, `SHA384`, and `SHA512`.

- Added the `Sign` database function.

- The new `is_dst` parameter of the `Trunc` database functions determines the treatment of nonexistent and ambiguous datetimes.

- `connection.queries` now shows `COPY … TO` statements on PostgreSQL.

- `FilePathField` now accepts a callable for `path`.

- Allowed symmetrical intermediate table for self-referential `ManyToManyField`.

- The `name` attributes of `CheckConstraint`, `UniqueConstraint`, and `Index` now support app label and class interpolation using the `'%(app_label)s'` and `'%(class)s'` placeholders.

- The new `Field.descriptor_class` attribute allows model fields to customize the get and set behavior by overriding their descriptors.

- `Avg` and `Sum` now support the `distinct` argument.

- Added `SmallAutoField` which acts much like an `AutoField` except that it only allows values under a certain (database-dependent) limit. Values from `1` to `32767` are safe in all databases supported by Django.

- `AutoField`, `BigAutoField`, and `SmallAutoField` now inherit from `IntegerField`, `BigIntegerField` and `SmallIntegerField` respectively. System checks and validators are now also properly inherited.

- `FileField.upload_to` now supports `pathlib.Path`.

- `CheckConstraint` is now supported on MySQL 8.0.16+.

- The new `allows_group_by_selected_pks_on_model()` method of `django.db.backends.base.BaseDatabaseFeatures` allows optimization of `GROUP BY` clauses to require only the selected models” primary keys. By default, it’s supported only for managed models on PostgreSQL.

  To enable the `GROUP BY` primary key-only optimization for unmanaged models, you have to subclass the PostgreSQL database engine, overriding the features class `allows_group_by_selected_pks_on_model()` method as you require. See Subclassing the built-in database backends for an example.

#### Requests and Responses

- Allowed `HttpResponse` to be initialized with `memoryview` content.

- For use in, for example, Django templates, `HttpRequest.headers` now allows lookups using underscores (e.g. `user_agent`) in place of hyphens.

#### Security

- `X_FRAME_OPTIONS` now defaults to `'DENY'`. In older versions, the `X_FRAME_OPTIONS` setting defaults to `'SAMEORIGIN'`. If your site uses frames of itself, you will need to explicitly set `X_FRAME_OPTIONS = 'SAMEORIGIN'` for them to continue working.

- `SECURE_CONTENT_TYPE_NOSNIFF` now defaults to `True`. With this enabled, `SecurityMiddleware` sets the X-Content-Type-Options: nosniff header on all responses that do not already have it.

- `SecurityMiddleware` can now send the Referrer-Policy header.

#### Tests

- The new test `Client` argument `raise_request_exception` allows controlling whether or not exceptions raised during the request should also be raised in the test. The value defaults to `True` for backwards compatibility. If it is `False` and an exception occurs, the test client will return a 500 response with the attribute `exc_info`, a tuple providing information of the exception that occurred.

- Tests and test cases to run can be selected by test name pattern using the new `test -k` option.

- HTML comparison, as used by `assertHTMLEqual()`, now treats text, character references, and entity references that refer to the same character as equivalent.

- `DiscoverRunner` can now spawn a debugger at each error or failure using the `test --pdb` option.

## Backwards incompatible changes in 3.0

### `Model.save()` when providing a default for the primary key

`Model.save()` no longer attempts to find a row when saving a new `Model` instance and a default value for the primary key is provided, and always performs a single `INSERT` query. In older Django versions, `Model.save()` performed either an `INSERT` or an `UPDATE` based on whether or not the row exists.

This makes calling `Model.save()` while providing a default primary key value equivalent to passing force_insert=True to model’s `save()`. Attempts to use a new `Model` instance to update an existing row will result in an `IntegrityError`.

In order to update an existing model for a specific primary key value, use the `update_or_create()` method or `QuerySet.filter(pk=…).update(…)` instead. For example:

    >>> MyModel.objects.update_or_create(pk=existing_pk, defaults={"name": "new name"})
    >>> MyModel.objects.filter(pk=existing_pk).update(name="new name")

### Database backend API

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

- The second argument of `DatabaseIntrospection.get_geometry_type()` is now the row description instead of the column name.

- `DatabaseIntrospection.get_field_type()` may no longer return tuples.

- If the database can create foreign keys in the same SQL statement that adds a field, add `SchemaEditor.sql_create_column_inline_fk` with the appropriate SQL; otherwise, set `DatabaseFeatures.can_create_inline_fk = False`.

- `DatabaseFeatures.can_return_id_from_insert` and `can_return_ids_from_bulk_insert` are renamed to `can_return_columns_from_insert` and `can_return_rows_from_bulk_insert`.

- Database functions now handle `datetime.timezone` formats when created using `datetime.timedelta` instances (e.g. `timezone(timedelta(hours=5))`, which would output `'UTC+05:00'`). Third-party backends should handle this format when preparing `DateTimeField` in `datetime_cast_date_sql()`, `datetime_extract_sql()`, etc.

- Entries for `AutoField`, `BigAutoField`, and `SmallAutoField` are added to `DatabaseOperations.integer_field_ranges` to support the integer range validators on these field types. Third-party backends may need to customize the default entries.

- `DatabaseOperations.fetch_returned_insert_id()` is replaced by `fetch_returned_insert_columns()` which returns a list of values returned by the `INSERT … RETURNING` statement, instead of a single value.

- `DatabaseOperations.return_insert_id()` is replaced by `return_insert_columns()` that accepts a `fields` argument, which is an iterable of fields to be returned after insert. Usually this is only the auto-generated primary key.

### `django.contrib.admin`

- Admin’s model history change messages now prefers more readable field labels instead of field names.

### `django.contrib.gis`

- Support for PostGIS 2.1 is removed.

- Support for SpatiaLite 4.1 and 4.2 is removed.

- Support for GDAL 1.11 and GEOS 3.4 is removed.

### Dropped support for PostgreSQL 9.4

Upstream support for PostgreSQL 9.4 ends in December 2019. Django 3.0 supports PostgreSQL 9.5 and higher.

### Dropped support for Oracle 12.1

Upstream support for Oracle 12.1 ends in July 2021. Django 2.2 will be supported until April 2022. Django 3.0 officially supports Oracle 12.2 and 18c.

### Removed private Python 2 compatibility APIs

While Python 2 support was removed in Django 2.0, some private APIs weren’t removed from Django so that third party apps could continue using them until the Python 2 end-of-life.

Since we expect apps to drop Python 2 compatibility when adding support for Django 3.0, we’re removing these APIs at this time.

- `django.test.utils.str_prefix()` - Strings don’t have “u” prefixes in Python 3.

- `django.test.utils.patch_logger()` - Use `unittest.TestCase.assertLogs()` instead.

- `django.utils.lru_cache.lru_cache()` - Alias of `functools.lru_cache()`.

- `django.utils.decorators.available_attrs()` - This function returns `functools.WRAPPER_ASSIGNMENTS`.

- `django.utils.decorators.ContextDecorator` - Alias of `contextlib.ContextDecorator`.

- `django.utils._os.abspathu()` - Alias of `os.path.abspath()`.

- `django.utils._os.upath()` and `npath()` - These functions do nothing on Python 3.

- `django.utils.six` - Remove usage of this vendored library or switch to six.

- `django.utils.encoding.python_2_unicode_compatible()` - Alias of `six.python_2_unicode_compatible()`.

- `django.utils.functional.curry()` - Use `functools.partial()` or `functools.partialmethod`. See 5b1c389603a353625ae1603ba345147356336afb.

- `django.utils.safestring.SafeBytes` - Unused since Django 2.0.

### New default value for the `FILE_UPLOAD_PERMISSIONS` setting

In older versions, the `FILE_UPLOAD_PERMISSIONS` setting defaults to `None`. With the default `FILE_UPLOAD_HANDLERS`, this results in uploaded files having different permissions depending on their size and which upload handler is used.

`FILE_UPLOAD_PERMISSIONS` now defaults to `0o644` to avoid this inconsistency.

### New default values for security settings

To make Django projects more secure by default, some security settings now have more secure default values:

- `X_FRAME_OPTIONS` now defaults to `'DENY'`.

- `SECURE_CONTENT_TYPE_NOSNIFF` now defaults to `True`.

See the What’s New Security section above for more details on these changes.

### Miscellaneous

- `ContentType.__str__()` now includes the model’s `app_label` to disambiguate models with the same name in different apps.

- Because accessing the language in the session rather than in the cookie is deprecated, `LocaleMiddleware` no longer looks for the user’s language in the session and `django.contrib.auth.logout()` no longer preserves the session’s language after logout.

- `django.utils.html.escape()` now uses `html.escape()` to escape HTML. This converts `'` to `&#x27;` instead of the previous equivalent decimal code `&#39;`.

- The `django-admin test -k` option now works as the `unittest -k` option rather than as a shortcut for `--keepdb`.

- Support for `pywatchman` < 1.2.0 is removed.

- `urlencode()` now encodes iterable values as they are when `doseq=False`, rather than iterating them, bringing it into line with the standard library `urllib.parse.urlencode()` function.

- `intword` template filter now translates `1.0` as a singular phrase and all other numeric values as plural. This may be incorrect for some languages.

- Assigning a value to a model’s `ForeignKey` or `OneToOneField` `'_id'` attribute now unsets the corresponding field. Accessing the field afterward will result in a query.

- `patch_vary_headers()` now handles an asterisk `'*'` according to RFC 7231 Section 7.1.4, i.e. if a list of header field names contains an asterisk, then the `Vary` header will consist of a single asterisk `'*'`.

- On MySQL 8.0.16+, `PositiveIntegerField` and `PositiveSmallIntegerField` now include a check constraint to prevent negative values in the database.

- `alias=None` is added to the signature of `Expression.get_group_by_cols()`.

- `RegexPattern`, used by `re_path()`, no longer returns keyword arguments with `None` values to be passed to the view for the optional named groups that are missing.

## Features deprecated in 3.0

### `django.utils.encoding.force_text()` and `smart_text()`

The `smart_text()` and `force_text()` aliases (since Django 2.0) of `smart_str()` and `force_str()` are deprecated. Ignore this deprecation if your code supports Python 2 as the behavior of `smart_str()` and `force_str()` is different there.

### Miscellaneous

- `django.utils.http.urlquote()`, `urlquote_plus()`, `urlunquote()`, and `urlunquote_plus()` are deprecated in favor of the functions that they’re aliases for: `urllib.parse.quote()`, `quote_plus()`, `unquote()`, and `unquote_plus()`.

- `django.utils.translation.ugettext()`, `ugettext_lazy()`, `ugettext_noop()`, `ungettext()`, and `ungettext_lazy()` are deprecated in favor of the functions that they’re aliases for: `django.utils.translation.gettext()`, `gettext_lazy()`, `gettext_noop()`, `ngettext()`, and `ngettext_lazy()`.

- To limit creation of sessions and hence favor some caching strategies, `django.views.i18n.set_language()` will stop setting the user’s language in the session in Django 4.0. Since Django 2.1, the language is always stored in the `LANGUAGE_COOKIE_NAME` cookie.

- `django.utils.text.unescape_entities()` is deprecated in favor of `html.unescape()`. Note that unlike `unescape_entities()`, `html.unescape()` evaluates lazy strings immediately.

- To avoid possible confusion as to effective scope, the private internal utility `is_safe_url()` is renamed to `url_has_allowed_host_and_scheme()`. That a URL has an allowed host and scheme doesn’t in general imply that it’s «safe». It may still be quoted incorrectly, for example. Ensure to also use `iri_to_uri()` on the path component of untrusted URLs.

## Features removed in 3.0

These features have reached the end of their deprecation cycle and are removed in Django 3.0.

See Features deprecated in 2.0 for details on these changes, including how to remove usage of these features.

- The `django.db.backends.postgresql_psycopg2` module is removed.

- `django.shortcuts.render_to_response()` is removed.

- The `DEFAULT_CONTENT_TYPE` setting is removed.

- `HttpRequest.xreadlines()` is removed.

- Support for the `context` argument of `Field.from_db_value()` and `Expression.convert_value()` is removed.

- The `field_name` keyword argument of `QuerySet.earliest()` and `latest()` is removed.

See Features deprecated in 2.1 for details on these changes, including how to remove usage of these features.

- The `ForceRHR` GIS function is removed.

- `django.utils.http.cookie_date()` is removed.

- The `staticfiles` and `admin_static` template tag libraries are removed.

- `django.contrib.staticfiles.templatetags.staticfiles.static()` is removed.