# Django 3.0.9.dev - dokumentacja

# 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:

    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.

Samodzielne skrypty

Własne komendy zarządcze są szczególnie przydatne w odpalaniu samodzielnych skryptów lub skryptów wykonywanych cyklicznie z tabeli programu cron Uniksa lub z panelu kontrolnego harmonogramu zadań Windows.

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

    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))

Informacja

Gdy używasz komend zarządczych i chcesz pisać na konsolę, powinieneś pisać na `self.stdout` i `self.stderr`, zamiast drukować bezpośrednio na `stdout` i `stderr`. Przy użyciu tych proxy, testowanie twojej komendy staje się dużo prostsze. Zwróć też uwagę, że nie potrzebujesz kończyć wiadomości znakiem końca linii. Zostanie on dodany automatycznie, chyba że podasz parametr `ending`:

    self.stdout.write("Unterminated line", ending='')

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:

    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:

    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:

      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.

Implementing a constructor in a subclass

If you implement `__init__` in your subclass of `BaseCommand`, you must call `BaseCommand`’s `__init__`:

    class Command(BaseCommand):
        def __init__(self, *args, **kwargs):
            super().__init__(*args, **kwargs)
            # ...

`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.

  Changed in Django 2.2:

  `kwargs` was added.

`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.

Calling a management command in your code

`execute()` should not be called directly from your code to execute a command. Use `call_command()` instead.

`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`

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 `call_command()`, it’s up to you to catch the exception when needed.