January 5, 2010
Welcome to Django 1.2 alpha 1!
This is the first in a series of preview/development releases leading up to the eventual release of Django 1.2, currently scheduled to take place in March 2010. This release is primarily targeted at developers who are interested in trying out new features and testing the Django codebase to help identify and resolve bugs prior to the final 1.2 release.
As such, this release is not intended for production use, and any such use is discouraged.
There have been large changes to the way that CSRF protection works, detailed in the CSRF documentaton. The following are the major changes that developers must be aware of:
Due to new features in the if template tag, it no longer accepts ‘and’, ‘or’ and ‘not’ as valid variable names. Previously that worked in some cases even though these strings were normally treated as keywords. Now, the keyword status is always enforced, and template code like {% if not %} or {% if and %} will throw a TemplateSyntaxError.
LazyObject is an undocumented utility class used for lazily wrapping other objects of unknown type. In Django 1.1 and earlier, it handled introspection in a non-standard way, depending on wrapped objects implementing a public method get_all_members(). Since this could easily lead to name clashes, it has been changed to use the standard method, involving __members__ and __dir__(). If you used LazyObject in your own code, and implemented the get_all_members() method for wrapped objects, you need to make the following changes:
If your class does not have special requirements for introspection (i.e. you have not implemented __getattr__() or other methods that allow for attributes not discoverable by normal mechanisms), you can simply remove the get_all_members() method. The default implementation on LazyObject will do the right thing.
If you have more complex requirements for introspection, first rename the get_all_members() method to __dir__(). This is the standard method, from Python 2.6 onwards, for supporting introspection. If you are require support for Python < 2.6, add the following code to the class:
__members__ = property(lambda self: self.__dir__())
Historically, the __dict__ attribute of a model instance has only contained attributes corresponding to the fields on a model.
In order to support multiple database configurations, Django 1.2 has added a _state attribute to object instances. This attribute will appear in __dict__ for a model instance. If your code relies on iterating over __dict__ to obtain a list of fields, you must now filter the _state attribute of out __dict__.
Prior to v1.2, a custom field had the option of defining several functions to support conversion of Python values into database-compatible values. A custom field might look something like:
class CustomModelField(models.Field):
# ...
def get_db_prep_save(self, value):
# ...
def get_db_prep_value(self, value):
# ...
def get_db_prep_lookup(self, lookup_type, value):
# ...
In 1.2, these three methods have undergone a change in prototype, and two extra methods have been introduced:
class CustomModelField(models.Field):
# ...
def get_prep_value(self, value):
# ...
def get_prep_lookup(self, lookup_type, value):
# ...
def get_db_prep_save(self, value, connection):
# ...
def get_db_prep_value(self, value, connection, prepared=False):
# ...
def get_db_prep_lookup(self, lookup_type, value, connection, prepared=False):
# ...
These changes are required to support multiple databases: get_db_prep_* can no longer make any assumptions regarding the database for which it is preparing. The connection argument now provides the preparation methods with the specific connection for which the value is being prepared.
The two new methods exist to differentiate general data preparation requirements, and requirements that are database-specific. The prepared argument is used to indicate to the database preparation methods whether generic value preparation has been performed. If an unprepared (i.e., prepared=False) value is provided to the get_db_prep_*() calls, they should invoke the corresponding get_prep_*() calls to perform generic data preparation.
Conversion functions has been provided which will transparently convert functions adhering to the old prototype into functions compatible with the new prototype. However, this conversion function will be removed in Django 1.4, so you should upgrade your Field definitions to use the new prototype.
If your get_db_prep_*() methods made no use of the database connection, you should be able to upgrade by renaming get_db_prep_value() to get_prep_value() and get_db_prep_lookup() to get_prep_lookup()`. If you require database specific conversions, then you will need to provide an implementation ``get_db_prep_* that uses the connection argument to resolve database-specific values.
Template tags that store rendering state on the node itself may experience problems if they are used with the new cached template loader.
All of the built-in Django template tags are safe to use with the cached loader, but if you're using custom template tags that come from third party packages, or that you wrote yourself, you should ensure that the Node implementation for each tag is thread-safe. For more information, see template tag thread safety considerations.
The exit status code of the test runners (tests/runtests.py and python manage.py test) no longer represents the number of failed tests, since a failure of 256 or more tests resulted in a wrong exit status code. The exit status code for the test runner is now 0 for success (no failing tests) and 1 for any number of test failures. If needed, the number of test failures can be found at the end of the test runner's output.
CsrfResponseMiddleware, the middleware that automatically inserted CSRF tokens into POST forms in outgoing pages, has been deprecated in favor of a template tag method (see above), and will be removed completely in Django 1.4. CsrfMiddleware, which includes the functionality of CsrfResponseMiddleware and CsrfViewMiddleware has likewise been deprecated.
Also, the CSRF module has moved from contrib to core, and the old imports are deprecated, as described in the upgrading notes.
The SMTPConnection class has been deprecated in favor of a generic E-mail backend API. Old code that explicitly instantiated an instance of an SMTPConnection:
from django.core.mail import SMTPConnection
connection = SMTPConnection()
messages = get_notification_email()
connection.send_messages(messages)
should now call get_connection() to instantiate a generic e-mail connection:
from django.core.mail import get_connection
connection = get_connection()
messages = get_notification_email()
connection.send_messages(messages)
Depending on the value of the EMAIL_BACKEND setting, this may not return an SMTP connection. If you explicitly require an SMTP connection with which to send e-mail, you can explicitly request an SMTP connection:
from django.core.mail import get_connection
connection = get_connection('django.core.mail.backends.smtp.EmailBackend')
messages = get_notification_email()
connection.send_messages(messages)
If your call to construct an instance of SMTPConnection required additional arguments, those arguments can be passed to the get_connection() call:
connection = get_connection('django.core.mail.backends.smtp.EmailBackend', hostname='localhost', port=1234)
Prior to Django 1.1, Django used a number of settings to control access to a single database. Django 1.2 introduces support for multiple databases, and as a result, the way you define database settings has changed.
Any existing Django settings file will continue to work as expected until Django 1.4. Old-style database settings will be automatically translated to the new-style format.
In the old-style (pre 1.2) format, there were a number of DATABASE_ settings at the top level of your settings file. For example:
DATABASE_NAME = 'test_db'
DATABASE_ENGINE = 'postgresql_psycopg2'
DATABASE_USER = 'myusername'
DATABASE_PASSWORD = 's3krit'
These settings are now contained inside a dictionary named DATABASES. Each item in the dictionary corresponds to a single database connection, with the name 'default' describing the default database connection. The setting names have also been shortened to reflect the fact that they are stored in a dictionary. The sample settings given previously would now be stored using:
DATABASES = {
'default': {
'NAME': 'test_db',
'ENGINE': 'django.db.backends.postgresql_psycopg2',
'USER': 'myusername',
'PASSWORD': 's3krit',
}
}
This affects the following settings:
These changes are also required if you have manually created a database connection using DatabaseWrapper() from your database backend of choice.
In addition to the change in structure, Django 1.2 removes the special handling for the built-in database backends. All database backends must now be specified by a fully qualified module name (i.e., django.db.backends.postgresql_psycopg2, rather than just postgresql_psycopg2).
The API for storing messages in the user Message model (via user.message_set.create) is now deprecated and will be removed in Django 1.4 according to the standard release process.
To upgrade your code, you need to replace any instances of:
user.message_set.create('a message')
with the following:
from django.contrib import messages
messages.add_message(request, messages.INFO, 'a message')
Additionally, if you make use of the method, you need to replace the following:
for message in user.get_and_delete_messages():
...
with:
from django.contrib import messages
for message in messages.get_messages(request):
...
For more information, see the full messages documentation. You should begin to update your code to use the new API immediately.
django.utils.translation.get_date_formats() and django.utils.translation.get_partial_date_formats() have been deprecated in favor of the appropriate calls to django.utils.formats.get_format() which is locale aware when USE_L10N is set to True, and falls back to default settings if set to False.
To get the different date formats, instead of writing:
from django.utils.translation import get_date_formats
date_format, datetime_format, time_format = get_date_formats()
use:
from django.utils import formats
date_format = formats.get_format('DATE_FORMAT')
datetime_format = formats.get_format('DATETIME_FORMAT')
time_format = formats.get_format('TIME_FORMAT')
or, when directly formatting a date value:
from django.utils import formats
value_formatted = formats.date_format(value, 'DATETIME_FORMAT')
The same applies to the globals found in django.forms.fields:
Use django.utils.formats.get_format() to get the appropriate formats.
The following new features are present as of this alpha release; this release also marks the end of major feature development for the 1.2 release cycle. Some minor features will continue development until the 1.2 beta release, however.
Django now has much improved protection against Cross-Site Request Forgery (CSRF) attacks. This type of attack occurs when a malicious Web site contains a link, a form button or some javascript that is intended to perform some action on your Web site, using the credentials of a logged-in user who visits the malicious site in their browser. A related type of attack, 'login CSRF', where an attacking site tricks a user's browser into logging into a site with someone else's credentials, is also covered.
You can now configure the way that Django sends e-mail. Instead of using SMTP to send all e-mail, you can now choose a configurable e-mail backend to send messages. If your hosting provider uses a sandbox or some other non-SMTP technique for sending mail, you can now construct an e-mail backend that will allow Django's standard mail sending methods to use those facilities.
This also makes it easier to debug mail sending - Django ships with backend implementations that allow you to send e-mail to a file, to the console, or to memory - you can even configure all e-mail to be thrown away.
Django now includes a robust and configurable messages framework with built-in support for cookie- and session-based messaging, for both anonymous and authenticated clients. The messages framework replaces the deprecated user message API and allows you to temporarily store messages in one request and retrieve them for display in a subsequent request (usually the next one).
Django 1.2 adds the ability to use more than one database in your Django project. Queries can be issued at a specific database with the using() method on querysets; individual objects can be saved to a specific database by providing a using argument when you save the instance.
The if tag has been upgraded to be much more powerful. First, support for comparison operators has been added. No longer will you have to type:
{% ifnotequal a b %}
...
{% endifnotequal %}
...as you can now do:
{% if a != b %}
...
{% endif %}
The operators supported are ==, !=, <, >, <=, >= and in, all of which work like the Python operators, in addition to and, or and not which were already supported.
Also, filters may now be used in the if expression. For example:
<div
{% if user.email|lower == message.recipient|lower %}
class="highlight"
{% endif %}
>{{ message }}</div>
In previous versions of Django, every time you rendered a template it would be reloaded from disk. In Django 1.2, you can use a cached template loader to load templates once, then use the cached result for every subsequent render. This can lead to a significant performance improvement if your templates are broken into lots of smaller subtemplates (using the {% extends %} or {% include %} tags).
As a side effect, it is now much easier to support non-Django template languages. For more details, see the notes on supporting non-Django template languages.
Fixtures can refer to remote objects using Natural keys. This lookup scheme is an alternative to the normal primary-key based object references in a fixture, improving readability, and resolving problems referring to objects whose primary key value may not be predictable or known.
Models can now use a 64 bit BigIntegerField type.
The test subcommand of django-admin.py, and the runtests.py script used to run Django's own test suite, support a new --failfast option. When specified, this option causes the test runner to exit after encountering a failure instead of continuing with the test run. In addition, the handling of Ctrl-C during a test run has been improved to trigger a graceful exit from the test run that reports details of the tests run before the interruption.
Django's internationalization framework has been expanded by locale aware formatting and form processing. That means, if enabled, dates and numbers on templates will be displayed using the format specified for the current locale. Django will also use localized formats when parsing data in forms. See Format localization for more details.
django.contrib.admin.ModelAdmin.readonly_fields has been added to enable non-editable fields in add/change pages for models and inlines. Field and calculated values can be displayed along side editable fields.
You can now use the DJANGO_COLORS environment variable to modify or disable the colors used by django-admin.py to provide syntax highlighting.
Before the final Django 1.2 release, several other preview/development releases will be made available. The current schedule consists of at least the following:
If necessary, additional alpha, beta or release-candidate packages will be issued prior to the final 1.2 release. Django 1.2 will be released approximately one week after the final release candidate.
In order to provide a high-quality 1.2 release, we need your help. Although this alpha release is, again, not intended for production use, you can help the Django team by trying out the alpha codebase in a safe test environment and reporting any bugs or issues you encounter. The Django ticket tracker is the central place to search for open issues:
Please open new tickets if no existing ticket corresponds to a problem you're running into.
Additionally, discussion of Django development, including progress toward the 1.2 release, takes place daily on the django-developers mailing list:
... and in the #django-dev IRC channel on irc.freenode.net. If you're interested in helping out with Django's development, feel free to join the discussions there.
Django's online documentation also includes pointers on how to contribute to Django:
Contributions on any level -- developing code, writing documentation or simply triaging tickets and helping to test proposed bugfixes -- are always welcome and appreciated.
Development sprints for Django 1.2 will also be taking place at PyCon US 2010, on the dedicated sprint days (February 22 through 25), and anyone who wants to help out is welcome to join in, either in person at PyCon or virtually in the IRC channel or on the mailing list.
Jul 05, 2010