# Documentazione Django 6.0.7

# Note di rilascio di Django 1.5

26 Febbraio 2013

Welcome to Django 1.5!

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 1.4 or older versions. We’ve also dropped some features, which are detailed in our deprecation plan, and we’ve begun the deprecation process for some features.

## Panoramica

The biggest new feature in Django 1.5 is the configurable User model. Before Django 1.5, applications that wanted to use Django’s auth framework (`django.contrib.auth`) were forced to use Django’s definition of a «user». In Django 1.5, you can now swap out the `User` model for one that you write yourself. This could be a simple extension to the existing `User` model – for example, you could add a Twitter or Facebook ID field – or you could completely replace the `User` with one totally customized for your site.

Django 1.5 is also the first release with Python 3 support! We’re labeling this support «experimental» because we don’t yet consider it production-ready, but everything’s in place for you to start porting your apps to Python 3. Our next release, Django 1.6, will support Python 3 without reservations.

Other notable new features in Django 1.5 include:

- Support for saving a subset of model’s fields - `Model.save()` now accepts an `update_fields` argument, letting you specify which fields are written back to the database when you call `save()`. This can help in high-concurrency operations, and can improve performance.

- Better support for streaming responses via the new `StreamingHttpResponse` response class.

- GeoDjango now supports PostGIS 2.0.

- … and more; see below.

Wherever possible we try to introduce new features in a backwards-compatible manner per our API stability policy. However, as with previous releases, Django 1.5 ships with some minor backwards incompatible changes; people upgrading from previous versions of Django should read that list carefully.

One deprecated feature worth noting is the shift to «new-style» `url` tag. Prior to Django 1.3, syntax like `{% url myview %}` was interpreted incorrectly (Django considered `"myview"` to be a literal name of a view, not a template variable named `myview`). Django 1.3 and above introduced the `{% load url from future %}` syntax to bring in the corrected behavior where `myview` was seen as a variable.

The upshot of this is that if you are not using `{% load url from future %}` in your templates, you’ll need to change tags like `{% url myview %}` to `{% url "myview" %}`. If you were using `{% load url from future %}` you can simply remove that line under Django 1.5

## Compatibilità con Python

Django 1.5 requires Python 2.6.5 or above, though we highly recommend Python 2.7.3 or above. Support for Python 2.5 and below has been dropped.

This change should affect only a small number of Django users, as most operating-system vendors today are shipping Python 2.6 or newer as their default version. If you’re still using Python 2.5, however, you’ll need to stick to Django 1.4 until you can upgrade your Python version. Per our support policy, Django 1.4 will continue to receive security support until the release of Django 1.6.

Django 1.5 does not run on a Jython final release, because Jython’s latest release doesn’t currently support Python 2.6. However, Jython currently does offer an alpha release featuring 2.7 support, and Django 1.5 supports that alpha release.

### Python 3 support

Django 1.5 introduces support for Python 3 - specifically, Python 3.2 and above. This comes in the form of a single codebase; you don’t need to install a different version of Django on Python 3. This means that you can write applications targeted for just Python 2, just Python 3, or single applications that support both platforms.

However, we’re labeling this support «experimental» for now: although it’s received extensive testing via our automated test suite, it’s received very little real-world testing. We’ve done our best to eliminate bugs, but we can’t be sure we covered all possible uses of Django.

Some features of Django aren’t available because they depend on third-party software that hasn’t been ported to Python 3 yet, including:

- the MySQL database backend (depends on MySQLdb)

- `ImageField` (depends on PIL)

- `LiveServerTestCase` (depends on Selenium WebDriver)

Further, Django’s more than a web framework; it’s an ecosystem of pluggable components. At this point, very few third-party applications have been ported to Python 3, so it’s unlikely that a real-world application will have all its dependencies satisfied under Python 3.

Thus, we’re recommending that Django 1.5 not be used in production under Python 3. Instead, use this opportunity to begin porting applications to Python 3. If you’re an author of a pluggable component, we encourage you to start porting now.

We plan to offer first-class, production-ready support for Python 3 in our next release, Django 1.6.

## What’s new in Django 1.5

### Configurable User model

In Django 1.5, you can now use your own model as the store for user-related data. If your project needs a username with more than 30 characters, or if you want to store user’s names in a format other than first name/last name, or you want to put custom profile information onto your User object, you can now do so.

If you have a third-party reusable application that references the User model, you may need to make some changes to the way you reference User instances. You should also document any specific features of the User model that your application relies upon.

See the documentation on custom user models for more details.

### Support for saving a subset of model’s fields

The method `Model.save()` has a new keyword argument `update_fields`. By using this argument it is possible to save only a select list of model’s fields. This can be useful for performance reasons or when trying to avoid overwriting concurrent changes.

Deferred instances (those loaded by `.only()` or `.defer()`) will automatically save just the loaded fields. If any field is set manually after load, that field will also get updated on save.

See the `Model.save()` documentation for more details.

### Caching of related model instances

When traversing relations, the ORM will avoid re-fetching objects that were previously loaded. For example, with the tutorial’s models:

    >>> first_poll = Poll.objects.all()[0]
    >>> first_choice = first_poll.choice_set.all()[0]
    >>> first_choice.poll is first_poll
    True

In Django 1.5, the third line no longer triggers a new SQL query to fetch `first_choice.poll`; it was set by the second line.

For one-to-one relationships, both sides can be cached. For many-to-one relationships, only the single side of the relationship can be cached. This is particularly helpful in combination with `prefetch_related`.

### Explicit support for streaming responses

Before Django 1.5, it was possible to create a streaming response by passing an iterator to `HttpResponse`. But this was unreliable: any middleware that accessed the `content` attribute would consume the iterator prematurely.

You can now explicitly generate a streaming response with the new `StreamingHttpResponse` class. This class exposes a `streaming_content` attribute which is an iterator.

Since `StreamingHttpResponse` does not have a `content` attribute, middleware that needs access to the response content must test for streaming responses and behave accordingly.

### `{% verbatim %}` template tag

To make it easier to deal with JavaScript templates which collide with Django’s syntax, you can now use the `verbatim` block tag to avoid parsing the tag’s content.

### Retrieval of `ContentType` instances associated with proxy models

The methods `ContentTypeManager.get_for_model()` and `ContentTypeManager.get_for_models()` have a new keyword argument – respectively `for_concrete_model` and `for_concrete_models`. By passing `False` using this argument it is now possible to retrieve the `ContentType` associated with proxy models.

### New `view` variable in class-based views context

In all generic class-based views (or any class-based view inheriting from `ContextMixin`), the context dictionary contains a `view` variable that points to the `View` instance.

### GeoDjango

- `LineString` and `MultiLineString` GEOS objects now support the `interpolate()` and `project()` methods (so-called linear referencing).

- The `wkb` and `hex` properties of `GEOSGeometry` objects preserve the Z dimension.

- Support for PostGIS 2.0 has been added and support for GDAL < 1.5 has been dropped.

### New tutorials

Additions to the docs include a revamped Tutorial 3 and a new tutorial on testing. A new section, «Advanced Tutorials», offers How to write reusable apps as well as a step-by-step guide for new contributors in Writing your first patch for Django.

### Minor features

Django 1.5 also includes several smaller improvements worth noting:

- The template engine now interprets `True`, `False` and `None` as the corresponding Python objects.

- `django.utils.timezone` provides a helper for converting aware datetimes between time zones. See `localtime()`.

- The generic views support OPTIONS requests.

- Management commands do not raise `SystemExit` any more when called by code from `call_command()`. Any exception raised by the command (mostly `CommandError`) is propagated.

  Moreover, when you output errors or messages in your custom commands, you should now use `self.stdout.write('message')` and `self.stderr.write('error')` (see the note on management commands output).

- The `dumpdata` management command outputs one row at a time, preventing out-of-memory errors when dumping large datasets.

- In the localflavor for Canada, `pq` was added to the acceptable codes for Quebec. It’s an old abbreviation.

- The receiver decorator is now able to connect to more than one signal by supplying a list of signals.

- In the admin, you can now filter users by groups which they are members of.

- `QuerySet.bulk_create()` now has a batch_size argument. By default the batch_size is unlimited except for SQLite where single batch is limited so that 999 parameters per query isn’t exceeded.

- The `LOGIN_URL` and `LOGIN_REDIRECT_URL` settings now also accept view function names and named URL patterns. This allows you to reduce configuration duplication. More information can be found in the `login_required()` documentation.

- Django now provides a mod_wsgi auth handler.

- The `QuerySet.delete()` and `Model.delete()` can now take fast-path in some cases. The fast-path allows for less queries and less objects fetched into memory. See `QuerySet.delete()` for details.

- An instance of `ResolverMatch` is stored on the request as `resolver_match`.

- By default, all logging messages reaching the `django` logger when `DEBUG` is `True` are sent to the console (unless you redefine the logger in your `LOGGING` setting).

- When using `RequestContext`, it is now possible to look up permissions by using `{% if 'someapp.someperm' in perms %}` in templates.

- It’s not required any more to have `404.html` and `500.html` templates in the root templates directory. Django will output some basic error messages for both situations when those templates are not found. It’s still recommended as good practice to provide those templates in order to present pretty error pages to the user.

- `django.contrib.auth` provides a new signal that is emitted whenever a user fails to login successfully. See `user_login_failed`

- The new `loaddata --ignorenonexistent` option ignore data for fields that no longer exist.

- `assertXMLEqual()` and `assertXMLNotEqual()` new assertions allow you to test equality for XML content at a semantic level, without caring for syntax differences (spaces, attribute order, etc.).

- RemoteUserMiddleware now forces logout when the REMOTE_USER header disappears during the same browser session.

- The cache-based session backend can store session data in a non-default cache.

- Multi-column indexes can now be created on models. Read the `index_together` documentation for more information.

- During Django’s logging configuration verbose Deprecation warnings are enabled and warnings are captured into the logging system. Logged warnings are routed through the `console` logging handler, which by default requires `DEBUG` to be True for output to be generated. The result is that DeprecationWarnings should be printed to the console in development environments the way they have been in Python versions < 2.7.

- The API for `django.contrib.admin.ModelAdmin.message_user()` method has been modified to accept additional arguments adding capabilities similar to `django.contrib.messages.add_message()`. This is useful for generating error messages from admin actions.

- The admin’s list filters can now be customized per-request thanks to the new `django.contrib.admin.ModelAdmin.get_list_filter()` method.

## Backwards incompatible changes in 1.5

Avvertimento

In addition to the changes outlined in this section, be sure to review the deprecation plan for any features that have been removed. If you haven’t updated your code within the deprecation timeline for a given feature, its removal may appear as a backwards incompatible change.

### `ALLOWED_HOSTS` required in production

The new `ALLOWED_HOSTS` setting validates the request’s `Host` header and protects against host-poisoning attacks. This setting is now required whenever `DEBUG` is `False`, or else `django.http.HttpRequest.get_host()` will raise `SuspiciousOperation`. For more details see the `full documentation` for the new setting.

### Managers on abstract models

Abstract models are able to define a custom manager, and that manager will be inherited by any concrete models extending the abstract model. However, if you try to use the abstract model to call a method on the manager, an exception will now be raised. Previously, the call would have been permitted, but would have failed as soon as any database operation was attempted (usually with a «table does not exist» error from the database).

If you have functionality on a manager that you have been invoking using the abstract class, you should migrate that logic to a Python `staticmethod` or `classmethod` on the abstract class.

### Context in year archive class-based views

For consistency with the other date-based generic views, `YearArchiveView` now passes `year` in the context as a `datetime.date` rather than a string. If you are using `{{ year }}` in your templates, you must replace it with `{{ year|date:"Y" }}`.

`next_year` and `previous_year` were also added in the context. They are calculated according to `allow_empty` and `allow_future`.

### Context in year and month archive class-based views

`YearArchiveView` and `MonthArchiveView` were documented to provide a `date_list` sorted in ascending order in the context, like their function-based predecessors, but it actually was in descending order. In 1.5, the documented order was restored. You may want to add (or remove) the `reversed` keyword when you’re iterating on `date_list` in a template:

    {% for date in date_list reversed %}

`ArchiveIndexView` still provides a `date_list` in descending order.

### Context in TemplateView

For consistency with the design of the other generic views, `TemplateView` no longer passes a `params` dictionary into the context, instead passing the variables from the URLconf directly into the context.

### Non-form data in HTTP requests

`request.POST` will no longer include data posted via HTTP requests with non form-specific content-types in the header. In prior versions, data posted with content-types other than multipart/form-data or application/x-www-form-urlencoded would still end up represented in the `request.POST` attribute. Developers wishing to access the raw POST data for these cases, should use the `request.body` attribute instead.

### `request_finished` signal

Django used to send the `request_finished` signal as soon as the view function returned a response. This interacted badly with streaming responses that delay content generation.

This signal is now sent after the content is fully consumed by the WSGI gateway. This might be backwards incompatible if you rely on the signal being fired before sending the response content to the client. If you do, you should consider using middleware instead.

Nota

Some WSGI servers and middleware do not always call `close` on the response object after handling a request, most notably uWSGI prior to 1.2.6 and Sentry’s error reporting middleware up to 2.0.7. In those cases the `request_finished` signal isn’t sent at all. This can result in idle connections to database and memcache servers.

### OPTIONS, PUT and DELETE requests in the test client

Unlike GET and POST, these HTTP methods aren’t implemented by web browsers. Rather, they’re used in APIs, which transfer data in various formats such as JSON or XML. Since such requests may contain arbitrary data, Django doesn’t attempt to decode their body.

However, the test client used to build a query string for OPTIONS and DELETE requests like for GET, and a request body for PUT requests like for POST. This encoding was arbitrary and inconsistent with Django’s behavior when it receives the requests, so it was removed in Django 1.5.

If you were using the `data` parameter in an OPTIONS or a DELETE request, you must convert it to a query string and append it to the `path` parameter.

If you were using the `data` parameter in a PUT request without a `content_type`, you must encode your data before passing it to the test client and set the `content_type` argument.

### System version of `simplejson` no longer used

As explained below, Django 1.5 deprecates `django.utils.simplejson` in favor of Python 2.6’s built-in `json` module. In theory, this change is harmless. Unfortunately, because of incompatibilities between versions of `simplejson`, it may trigger errors in some circumstances.

JSON-related features in Django 1.4 always used `django.utils.simplejson`. This module was actually:

- A system version of `simplejson`, if one was available (i.e. `import simplejson` works), if it was more recent than Django’s built-in copy or it had the C speedups, or

- The `json` module from the standard library, if it was available (i.e. Python 2.6 or greater), or

- A built-in copy of version 2.0.7 of `simplejson`.

In Django 1.5, those features use Python’s `json` module, which is based on version 2.0.9 of `simplejson`.

There are no known incompatibilities between Django’s copy of version 2.0.7 and Python’s copy of version 2.0.9. However, there are some incompatibilities between other versions of `simplejson`:

- While the `simplejson` API is documented as always returning Unicode strings, the optional C implementation can return a bytestring. This was fixed in Python 2.7.

- `simplejson.JSONEncoder` gained a `namedtuple_as_object` keyword argument in version 2.2.

More information on these incompatibilities is available in ticket #18023.

The net result is that, if you have installed `simplejson` and your code uses Django’s serialization internals directly – for instance `django.core.serializers.json.DjangoJSONEncoder`, the switch from `simplejson` to `json` could break your code. (In general, changes to internals aren’t documented; we’re making an exception here.)

At this point, the maintainers of Django believe that using `json` from the standard library offers the strongest guarantee of backwards-compatibility. They recommend to use it from now on.

### String types of hasher method parameters

If you have written a custom password hasher, your `encode()`, `verify()` or `safe_summary()` methods should accept Unicode parameters (`password`, `salt` or `encoded`). If any of the hashing methods need bytestrings, you can use the `force_bytes()` utility to encode the strings.

### Validation of previous_page_number and next_page_number

When using object pagination, the `previous_page_number()` and `next_page_number()` methods of the `Page` object did not check if the returned number was inside the existing page range. It does check it now and raises an `InvalidPage` exception when the number is either too low or too high.

### Behavior of autocommit database option on PostgreSQL changed

PostgreSQL’s autocommit option didn’t work as advertised previously. It did work for single transaction block, but after the first block was left the autocommit behavior was never restored. This bug is now fixed in 1.5. While this is only a bug fix, it is worth checking your applications behavior if you are using PostgreSQL together with the autocommit option.

### Session not saved on 500 responses

Django’s session middleware will skip saving the session data if the response’s status code is 500.

### Email checks on failed admin login

Prior to Django 1.5, if you attempted to log into the admin interface and mistakenly used your email address instead of your username, the admin interface would provide a warning advising that your email address was not your username. In Django 1.5, the introduction of custom user models has required the removal of this warning. This doesn’t change the login behavior of the admin site; it only affects the warning message that is displayed under one particular mode of login failure.

### Changes in tests execution

Some changes have been introduced in the execution of tests that might be backward-incompatible for some testing setups:

#### Database flushing in `django.test.TransactionTestCase`

Previously, the test database was truncated before each test run in a `TransactionTestCase`.

In order to be able to run unit tests in any order and to make sure they are always isolated from each other, `TransactionTestCase` will now reset the database after each test run instead.

#### No more implicit DB sequences reset

`TransactionTestCase` tests used to reset primary key sequences automatically together with the database flushing actions described above.

This has been changed so no sequences are implicitly reset. This can cause `TransactionTestCase` tests that depend on hardcoded primary key values to break.

The new `reset_sequences` attribute can be used to force the old behavior for `TransactionTestCase` that might need it.

#### Ordering of tests

In order to make sure all `TestCase` code starts with a clean database, tests are now executed in the following order:

- First, all unit tests (including `unittest.TestCase`, `SimpleTestCase`, `TestCase` and `TransactionTestCase`) are run with no particular ordering guaranteed nor enforced among them.

- Then any other tests (e.g. doctests) that may alter the database without restoring it to its original state are run.

This should not cause any problems unless you have existing doctests which assume a `TransactionTestCase` executed earlier left some database state behind or unit tests that rely on some form of state being preserved after the execution of other tests. Such tests are already very fragile, and must now be changed to be able to run independently.

### `cleaned_data` dictionary kept for invalid forms

The `cleaned_data` dictionary is now always present after form validation. When the form doesn’t validate, it contains only the fields that passed validation. You should test the success of the validation with the `is_valid()` method and not with the presence or absence of the `cleaned_data` attribute on the form.

### Behavior of `syncdb` with multiple databases

`syncdb` now queries the database routers to determine if content types (when `contenttypes` is enabled) and permissions (when `auth` is enabled) should be created in the target database. Previously, it created them in the default database, even when another database was specified with the `--database` option.

If you use `syncdb` on multiple databases, you should ensure that your routers allow synchronizing content types and permissions to only one of them. See the docs on the behavior of contrib apps with multiple databases for more information.

### XML deserializer will not parse documents with a DTD

In order to prevent exposure to denial-of-service attacks related to external entity references and entity expansion, the XML model deserializer now refuses to parse XML documents containing a DTD (DOCTYPE definition). Since the XML serializer does not output a DTD, this will not impact typical usage, only cases where custom-created XML documents are passed to Django’s model deserializer.

### Formsets default `max_num`

A (default) value of `None` for the `max_num` argument to a formset factory no longer defaults to allowing any number of forms in the formset. Instead, in order to prevent memory-exhaustion attacks, it now defaults to a limit of 1000 forms. This limit can be raised by explicitly setting a higher value for `max_num`.

### Miscellanea

- `django.forms.ModelMultipleChoiceField` now returns an empty `QuerySet` as the empty value instead of an empty list.

- `int_to_base36()` properly raises a `TypeError` instead of `ValueError` for non-integer inputs.

- The `slugify` template filter is now available as a standard Python function at `django.utils.text.slugify()`. Similarly, `remove_tags` is available at `django.utils.html.remove_tags()`.

- Uploaded files are no longer created as executable by default. If you need them to be executable change `FILE_UPLOAD_PERMISSIONS` to your needs. The new default value is `0o666` (octal) and the current umask value is first masked out.

- The `F expressions` supported bitwise operators by `&` and `|`. These operators are now available using `.bitand()` and `.bitor()` instead. The removal of `&` and `|` was done to be consistent with Q() expressions and `QuerySet` combining where the operators are used as boolean AND and OR operators.

- In a `filter()` call, when `F expressions` contained lookups spanning multi-valued relations, they didn’t always reuse the same relations as other lookups along the same chain. This was changed, and now F() expressions will always use the same relations as other lookups within the same `filter()` call.

- The `csrf_token` template tag is no longer enclosed in a div. If you need HTML validation against pre-HTML5 Strict DTDs, you should add a div around it in your pages.

- The template tags library `adminmedia`, which only contained the deprecated template tag `{% admin_media_prefix %}`, was removed. Attempting to load it with `{% load adminmedia %}` will fail. If your templates still contain that line you must remove it.

- Because of an implementation oversight, it was possible to use django.contrib.redirects without enabling django.contrib.sites. This isn’t allowed any longer. If you’re using `django.contrib.redirects`, make sure `INSTALLED_APPS` contains `django.contrib.sites`.

- `BoundField.label_tag` now escapes its `contents` argument. To avoid the HTML escaping, use `django.utils.safestring.mark_safe()` on the argument before passing it.

- Accessing reverse one-to-one relations fetched via `select_related()` now raises `DoesNotExist` instead of returning `None`.

## Features deprecated in 1.5

### `django.contrib.localflavor`

The localflavor contrib app has been split into separate packages. `django.contrib.localflavor` itself will be removed in Django 1.6, after an accelerated deprecation.

The new packages are available on GitHub. The core team cannot efficiently maintain these packages in the long term — it spans just a dozen countries at this time; similar to translations, maintenance will be handed over to interested members of the community.

### `django.contrib.markup`

The markup contrib module has been deprecated and will follow an accelerated deprecation schedule. Direct use of Python markup libraries or 3rd party tag libraries is preferred to Django maintaining this functionality in the framework.

### `AUTH_PROFILE_MODULE`

With the introduction of custom user models, there is no longer any need for a built-in mechanism to store user profile data.

You can still define user profiles models that have a one-to-one relation with the User model - in fact, for many applications needing to associate data with a User account, this will be an appropriate design pattern to follow. However, the `AUTH_PROFILE_MODULE` setting, and the `django.contrib.auth.models.User.get_profile()` method for accessing the user profile model, should not be used any longer.

### Streaming behavior of `HttpResponse`

Django 1.5 deprecates the ability to stream a response by passing an iterator to `HttpResponse`. If you rely on this behavior, switch to `StreamingHttpResponse`. See Explicit support for streaming responses above.

In Django 1.7 and above, the iterator will be consumed immediately by `HttpResponse`.

### `django.utils.simplejson`

Since Django 1.5 drops support for Python 2.5, we can now rely on the `json` module being available in Python’s standard library, so we’ve removed our own copy of `simplejson`. You should now import `json` instead of `django.utils.simplejson`.

Unfortunately, this change might have unwanted side-effects, because of incompatibilities between versions of `simplejson` – see the backwards-incompatible changes section. If you rely on features added to `simplejson` after it became Python’s `json`, you should import `simplejson` explicitly.

### `django.utils.encoding.StrAndUnicode`

The `django.utils.encoding.StrAndUnicode` mix-in has been deprecated. Define a `__str__` method and apply the `django.utils.encoding.python_2_unicode_compatible` decorator instead.

### `django.utils.itercompat.product`

The `django.utils.itercompat.product` function has been deprecated. Use the built-in `itertools.product()` instead.

### `cleanup` management command

The `cleanup` management command has been deprecated and replaced by `clearsessions`.

### `daily_cleanup.py` script

The undocumented `daily_cleanup.py` script has been deprecated. Use the `clearsessions` management command instead.

### `depth` keyword argument in `select_related`

The `depth` keyword argument in `select_related()` has been deprecated. You should use field names instead.