djangodocs

Django 3.1
Polski
Documentation contents

Pisanie własnych komend django-admin

Aplikacje mogą rejestrować swoje własne akcje w manage.py. Na przykład mógłbyś chcieć dodać akcję manage.py dla aplikacji Django, którą udostępniasz. W tym dokumencie będziemy budować własną komendę closepoll dla aplikacji polls z samouczka.

Aby to zrobić, dodaj katalog management/commands do aplikacji. Django zarejestruje komendę manage.py dla każdego modułu Pythona w tym katalogu, którego nazwa nie zaczyna się od znaku podkreślenia. Na przykład:

Code
polls/
    __init__.py
    models.py
    management/
        commands/
            _private.py
            closepoll.py
    tests.py
    views.py

W tym przykładzie komenda closepoll stanie się dostępna dla każdego projektu, który umieści aplikację polls w INSTALLED_APPS.

Moduł _private.py nie będzie dostępny jako komenda zarządzania.

Jest tylko jedno wymaganie dla closepoll.py – musi definiować klasę Command, która dziedziczy po BaseCommand lub jednej z jej podklas.

Aby zaimplementować komendę, zmień polls/management/commands/closepoll.py, aby wyglądał w ten sposób:

Code
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_ids', nargs='+', type=int)

    def handle(self, *args, **options):
        for poll_id in options['poll_ids']:
            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))

The new custom command can be called using python manage.py closepoll <poll_ids>.

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 CommandError is raised. The poll.opened attribute does not exist in the tutorial and was added to polls.models.Question for this example.

Akceptowanie opcjonalnych argumentów

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 add_arguments() method like this:

Code
class Command(BaseCommand):
    def add_arguments(self, parser):
        # Positional arguments
        parser.add_argument('poll_ids', nargs='+', type=int)

        # Named (optional) arguments
        parser.add_argument(
            '--delete',
            action='store_true',
            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 argparse Python documentation for more about add_argument usage.

In addition to being able to add custom command line options, all management commands can accept some default options such as --verbosity and --traceback.

Management commands and locales

By default, management commands are executed with the current active locale.

If, for some reason, your custom management command must run without an active locale (for example, to prevent translated content from being inserted into the database), deactivate translations using the @no_translations decorator on your handle() method:

Code
from django.core.management.base import BaseCommand, no_translations

class Command(BaseCommand):
    ...

    @no_translations
    def handle(self, *args, **options):
        ...

Since translation deactivation requires access to configured settings, the decorator can’t be used for commands that work without configured settings.

Testowanie

Information on how to test custom management commands can be found in the testing docs.

Overriding commands

Django registers the built-in commands and then searches for commands in 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 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 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 subclasses.

Subclassing the BaseCommand class requires that you implement the handle() method.

Atrybuty

All attributes can be set in your derived class and can be used in BaseCommand’s subclasses.

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>.

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 argparse („too few arguments”).

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.

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.

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.

BaseCommand.style

An instance attribute that helps create colored output when writing to stdout or stderr. For example:

Code
self.stdout.write(self.style.SUCCESS('...'))

See 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 --no-color option when running your command, all self.style() calls will return the original string uncolored.

Metody

BaseCommand has a few methods that can be overridden but only the handle() method must be implemented.

BaseCommand.create_parser(prog_name, subcommand, **kwargs)

Returns a CommandParser instance, which is an ArgumentParser subclass with a few customizations for Django.

You can customize the instance by overriding this method and calling super() with kwargs of ArgumentParser parameters.

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.

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.

BaseCommand.execute(*args, **options)

Tries to execute this command, performing system checks if needed (as controlled by the requires_system_checks attribute). If the command raises a CommandError, it’s intercepted and printed to stderr.

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 output_transaction is True).

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 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.

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 handle(), subclasses must implement handle_app_config(), which will be called once for each application.

AppCommand.handle_app_config(app_config, **options)

Perform the command’s actions for app_config, which will be an 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 handle(), subclasses must implement handle_label(), which will be called once for each label.

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'.

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(returncode=1)

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. It accepts the optional returncode argument to customize the exit status for the management command to exit with, using sys.exit().

If a management command is called from code through call_command(), it’s up to you to catch the exception when needed.

View as Markdown Edit this page on GitHub Official version