393 lines
15 KiB
Plaintext
393 lines
15 KiB
Plaintext
========================================
|
||
Writing custom ``django-admin`` commands
|
||
========================================
|
||
|
||
.. module:: django.core.management
|
||
|
||
Applications can register their own actions with ``manage.py``. For example,
|
||
you might want to add a ``manage.py`` action for a Django app that you're
|
||
distributing. In this document, we will be building a custom ``closepoll``
|
||
command for the ``polls`` application from the
|
||
:doc:`tutorial</intro/tutorial01>`.
|
||
|
||
To do this, just add a ``management/commands`` directory to the application.
|
||
Django will register a ``manage.py`` command for each Python module in that
|
||
directory whose name doesn't begin with an underscore. For example::
|
||
|
||
polls/
|
||
__init__.py
|
||
models.py
|
||
management/
|
||
__init__.py
|
||
commands/
|
||
__init__.py
|
||
_private.py
|
||
closepoll.py
|
||
tests.py
|
||
views.py
|
||
|
||
In this example, the ``closepoll`` command will be made available to any project
|
||
that includes the ``polls`` application in :setting:`INSTALLED_APPS`.
|
||
|
||
The ``_private.py`` module will not be available as a management command.
|
||
|
||
The ``closepoll.py`` module has only one requirement -- it must define a class
|
||
``Command`` that extends :class:`BaseCommand` or one of its
|
||
:ref:`subclasses<ref-basecommand-subclasses>`.
|
||
|
||
.. admonition:: Standalone scripts
|
||
|
||
Custom management commands are especially useful for running standalone
|
||
scripts or for scripts that are periodically executed from the UNIX crontab
|
||
or from Windows scheduled tasks control panel.
|
||
|
||
To implement the command, edit ``polls/management/commands/closepoll.py`` to
|
||
look like this::
|
||
|
||
from django.core.management.base import BaseCommand, CommandError
|
||
from polls.models import Question as Poll
|
||
|
||
class Command(BaseCommand):
|
||
help = 'Closes the specified poll for voting'
|
||
|
||
def add_arguments(self, parser):
|
||
parser.add_argument('poll_id', nargs='+', type=int)
|
||
|
||
def handle(self, *args, **options):
|
||
for poll_id in options['poll_id']:
|
||
try:
|
||
poll = Poll.objects.get(pk=poll_id)
|
||
except Poll.DoesNotExist:
|
||
raise CommandError('Poll "%s" does not exist' % poll_id)
|
||
|
||
poll.opened = False
|
||
poll.save()
|
||
|
||
self.stdout.write(self.style.SUCCESS('Successfully closed poll "%s"' % poll_id))
|
||
|
||
.. _management-commands-output:
|
||
|
||
.. note::
|
||
When you are using management commands and wish to provide console
|
||
output, you should write to ``self.stdout`` and ``self.stderr``,
|
||
instead of printing to ``stdout`` and ``stderr`` directly. By
|
||
using these proxies, it becomes much easier to test your custom
|
||
command. Note also that you don't need to end messages with a newline
|
||
character, it will be added automatically, unless you specify the ``ending``
|
||
parameter::
|
||
|
||
self.stdout.write("Unterminated line", ending='')
|
||
|
||
The new custom command can be called using ``python manage.py closepoll
|
||
<poll_id>``.
|
||
|
||
The ``handle()`` method takes one or more ``poll_ids`` and sets ``poll.opened``
|
||
to ``False`` for each one. If the user referenced any nonexistent polls, a
|
||
:exc:`CommandError` is raised. The ``poll.opened`` attribute does not exist in
|
||
the :doc:`tutorial</intro/tutorial01>` and was added to
|
||
``polls.models.Question`` for this example.
|
||
|
||
.. _custom-commands-options:
|
||
|
||
Accepting optional arguments
|
||
============================
|
||
|
||
The same ``closepoll`` could be easily modified to delete a given poll instead
|
||
of closing it by accepting additional command line options. These custom
|
||
options can be added in the :meth:`~BaseCommand.add_arguments` method like this::
|
||
|
||
class Command(BaseCommand):
|
||
def add_arguments(self, parser):
|
||
# Positional arguments
|
||
parser.add_argument('poll_id', nargs='+', type=int)
|
||
|
||
# Named (optional) arguments
|
||
parser.add_argument(
|
||
'--delete',
|
||
action='store_true',
|
||
dest='delete',
|
||
help='Delete poll instead of closing it',
|
||
)
|
||
|
||
def handle(self, *args, **options):
|
||
# ...
|
||
if options['delete']:
|
||
poll.delete()
|
||
# ...
|
||
|
||
The option (``delete`` in our example) is available in the options dict
|
||
parameter of the handle method. See the :py:mod:`argparse` Python documentation
|
||
for more about ``add_argument`` usage.
|
||
|
||
In addition to being able to add custom command line options, all
|
||
:doc:`management commands</ref/django-admin>` can accept some default options
|
||
such as :option:`--verbosity` and :option:`--traceback`.
|
||
|
||
.. _management-commands-and-locales:
|
||
|
||
Management commands and locales
|
||
===============================
|
||
|
||
By default, the :meth:`BaseCommand.execute` method deactivates translations
|
||
because some commands shipped with Django perform several tasks (for example,
|
||
user-facing content rendering and database population) that require a
|
||
project-neutral string language.
|
||
|
||
If, for some reason, your custom management command needs to use a fixed locale,
|
||
you should manually activate and deactivate it in your
|
||
:meth:`~BaseCommand.handle` method using the functions provided by the I18N
|
||
support code::
|
||
|
||
from django.core.management.base import BaseCommand, CommandError
|
||
from django.utils import translation
|
||
|
||
class Command(BaseCommand):
|
||
...
|
||
|
||
def handle(self, *args, **options):
|
||
|
||
# Activate a fixed locale, e.g. Russian
|
||
translation.activate('ru')
|
||
|
||
# Or you can activate the LANGUAGE_CODE # chosen in the settings:
|
||
from django.conf import settings
|
||
translation.activate(settings.LANGUAGE_CODE)
|
||
|
||
# Your command logic here
|
||
...
|
||
|
||
translation.deactivate()
|
||
|
||
Another need might be that your command simply should use the locale set in
|
||
settings and Django should be kept from deactivating it. You can achieve
|
||
it by using the :data:`BaseCommand.leave_locale_alone` option.
|
||
|
||
When working on the scenarios described above though, take into account that
|
||
system management commands typically have to be very careful about running in
|
||
non-uniform locales, so you might need to:
|
||
|
||
* Make sure the :setting:`USE_I18N` setting is always ``True`` when running
|
||
the command (this is a good example of the potential problems stemming
|
||
from a dynamic runtime environment that Django commands avoid offhand by
|
||
deactivating translations).
|
||
|
||
* Review the code of your command and the code it calls for behavioral
|
||
differences when locales are changed and evaluate its impact on
|
||
predictable behavior of your command.
|
||
|
||
Testing
|
||
=======
|
||
|
||
Information on how to test custom management commands can be found in the
|
||
:ref:`testing docs <topics-testing-management-commands>`.
|
||
|
||
Overriding commands
|
||
===================
|
||
|
||
Django registers the built-in commands and then searches for commands in
|
||
:setting:`INSTALLED_APPS` in reverse. During the search, if a command name
|
||
duplicates an already registered command, the newly discovered command
|
||
overrides the first.
|
||
|
||
In other words, to override a command, the new command must have the same name
|
||
and its app must be before the overridden command's app in
|
||
:setting:`INSTALLED_APPS`.
|
||
|
||
Management commands from third-party apps that have been unintentionally
|
||
overridden can be made available under a new name by creating a new command in
|
||
one of your project's apps (ordered before the third-party app in
|
||
:setting:`INSTALLED_APPS`) which imports the ``Command`` of the overridden
|
||
command.
|
||
|
||
Command objects
|
||
===============
|
||
|
||
.. class:: BaseCommand
|
||
|
||
The base class from which all management commands ultimately derive.
|
||
|
||
Use this class if you want access to all of the mechanisms which
|
||
parse the command-line arguments and work out what code to call in
|
||
response; if you don't need to change any of that behavior,
|
||
consider using one of its :ref:`subclasses<ref-basecommand-subclasses>`.
|
||
|
||
Subclassing the :class:`BaseCommand` class requires that you implement the
|
||
:meth:`~BaseCommand.handle` method.
|
||
|
||
Attributes
|
||
----------
|
||
|
||
All attributes can be set in your derived class and can be used in
|
||
:class:`BaseCommand`’s :ref:`subclasses<ref-basecommand-subclasses>`.
|
||
|
||
.. attribute:: BaseCommand.help
|
||
|
||
A short description of the command, which will be printed in the
|
||
help message when the user runs the command
|
||
``python manage.py help <command>``.
|
||
|
||
.. attribute:: BaseCommand.missing_args_message
|
||
|
||
If your command defines mandatory positional arguments, you can customize
|
||
the message error returned in the case of missing arguments. The default is
|
||
output by :py:mod:`argparse` ("too few arguments").
|
||
|
||
.. attribute:: BaseCommand.output_transaction
|
||
|
||
A boolean indicating whether the command outputs SQL statements; if
|
||
``True``, the output will automatically be wrapped with ``BEGIN;`` and
|
||
``COMMIT;``. Default value is ``False``.
|
||
|
||
.. attribute:: BaseCommand.requires_migrations_checks
|
||
|
||
A boolean; if ``True``, the command prints a warning if the set of
|
||
migrations on disk don't match the migrations in the database. A warning
|
||
doesn't prevent the command from executing. Default value is ``False``.
|
||
|
||
.. attribute:: BaseCommand.requires_system_checks
|
||
|
||
A boolean; if ``True``, the entire Django project will be checked for
|
||
potential problems prior to executing the command. Default value is ``True``.
|
||
|
||
.. attribute:: BaseCommand.leave_locale_alone
|
||
|
||
A boolean indicating whether the locale set in settings should be preserved
|
||
during the execution of the command instead of translations being
|
||
deactivated.
|
||
|
||
Default value is ``False``.
|
||
|
||
Make sure you know what you are doing if you decide to change the value of
|
||
this option in your custom command if it creates database content that
|
||
is locale-sensitive and such content shouldn't contain any translations
|
||
(like it happens e.g. with :mod:`django.contrib.auth` permissions) as
|
||
activating any locale might cause unintended effects. See the `Management
|
||
commands and locales`_ section above for further details.
|
||
|
||
.. attribute:: BaseCommand.style
|
||
|
||
An instance attribute that helps create colored output when writing to
|
||
``stdout`` or ``stderr``. For example::
|
||
|
||
self.stdout.write(self.style.SUCCESS('...'))
|
||
|
||
See :ref:`syntax-coloring` to learn how to modify the color palette and to
|
||
see the available styles (use uppercased versions of the "roles" described
|
||
in that section).
|
||
|
||
If you pass the :option:`--no-color` option when running your command, all
|
||
``self.style()`` calls will return the original string uncolored.
|
||
|
||
Methods
|
||
-------
|
||
|
||
:class:`BaseCommand` has a few methods that can be overridden but only
|
||
the :meth:`~BaseCommand.handle` method must be implemented.
|
||
|
||
.. admonition:: Implementing a constructor in a subclass
|
||
|
||
If you implement ``__init__`` in your subclass of :class:`BaseCommand`,
|
||
you must call :class:`BaseCommand`’s ``__init__``::
|
||
|
||
class Command(BaseCommand):
|
||
def __init__(self, *args, **kwargs):
|
||
super().__init__(*args, **kwargs)
|
||
# ...
|
||
|
||
.. method:: BaseCommand.add_arguments(parser)
|
||
|
||
Entry point to add parser arguments to handle command line arguments passed
|
||
to the command. Custom commands should override this method to add both
|
||
positional and optional arguments accepted by the command. Calling
|
||
``super()`` is not needed when directly subclassing ``BaseCommand``.
|
||
|
||
.. method:: BaseCommand.get_version()
|
||
|
||
Returns the Django version, which should be correct for all built-in Django
|
||
commands. User-supplied commands can override this method to return their
|
||
own version.
|
||
|
||
.. method:: BaseCommand.execute(*args, **options)
|
||
|
||
Tries to execute this command, performing system checks if needed (as
|
||
controlled by the :attr:`requires_system_checks` attribute). If the command
|
||
raises a :exc:`CommandError`, it's intercepted and printed to stderr.
|
||
|
||
.. admonition:: Calling a management command in your code
|
||
|
||
``execute()`` should not be called directly from your code to execute a
|
||
command. Use :func:`~django.core.management.call_command` instead.
|
||
|
||
.. method:: BaseCommand.handle(*args, **options)
|
||
|
||
The actual logic of the command. Subclasses must implement this method.
|
||
|
||
It may return a string which will be printed to ``stdout`` (wrapped
|
||
by ``BEGIN;`` and ``COMMIT;`` if :attr:`output_transaction` is ``True``).
|
||
|
||
.. method:: BaseCommand.check(app_configs=None, tags=None, display_num_errors=False)
|
||
|
||
Uses the system check framework to inspect the entire Django project for
|
||
potential problems. Serious problems are raised as a :exc:`CommandError`;
|
||
warnings are output to stderr; minor notifications are output to stdout.
|
||
|
||
If ``app_configs`` and ``tags`` are both ``None``, all system checks are
|
||
performed. ``tags`` can be a list of check tags, like ``compatibility`` or
|
||
``models``.
|
||
|
||
.. _ref-basecommand-subclasses:
|
||
|
||
``BaseCommand`` subclasses
|
||
--------------------------
|
||
|
||
.. class:: AppCommand
|
||
|
||
A management command which takes one or more installed application labels as
|
||
arguments, and does something with each of them.
|
||
|
||
Rather than implementing :meth:`~BaseCommand.handle`, subclasses must
|
||
implement :meth:`~AppCommand.handle_app_config`, which will be called once for
|
||
each application.
|
||
|
||
.. method:: AppCommand.handle_app_config(app_config, **options)
|
||
|
||
Perform the command's actions for ``app_config``, which will be an
|
||
:class:`~django.apps.AppConfig` instance corresponding to an application
|
||
label given on the command line.
|
||
|
||
.. class:: LabelCommand
|
||
|
||
A management command which takes one or more arbitrary arguments (labels) on
|
||
the command line, and does something with each of them.
|
||
|
||
Rather than implementing :meth:`~BaseCommand.handle`, subclasses must implement
|
||
:meth:`~LabelCommand.handle_label`, which will be called once for each label.
|
||
|
||
.. attribute:: LabelCommand.label
|
||
|
||
A string describing the arbitrary arguments passed to the command. The
|
||
string is used in the usage text and error messages of the command.
|
||
Defaults to ``'label'``.
|
||
|
||
.. method:: LabelCommand.handle_label(label, **options)
|
||
|
||
Perform the command's actions for ``label``, which will be the string as
|
||
given on the command line.
|
||
|
||
Command exceptions
|
||
------------------
|
||
|
||
.. exception:: CommandError
|
||
|
||
Exception class indicating a problem while executing a management command.
|
||
|
||
If this exception is raised during the execution of a management command from a
|
||
command line console, it will be caught and turned into a nicely-printed error
|
||
message to the appropriate output stream (i.e., stderr); as a result, raising
|
||
this exception (with a sensible description of the error) is the preferred way
|
||
to indicate that something has gone wrong in the execution of a command.
|
||
|
||
If a management command is called from code through
|
||
:func:`~django.core.management.call_command`, it's up to you to catch the
|
||
exception when needed.
|