django-admin commands¶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
tutorial.
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
On Python 2, be sure to include __init__.py files in both the
management and management/commands directories as done above or your
command will not be detected.
In this example, the closepoll command will be made available to any project
that includes the polls application in 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 BaseCommand or one of its
subclasses.
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))
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
CommandError is raised. The poll.opened attribute does not exist in
the tutorial and was added to
polls.models.Question for this example.
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_id', nargs='+', type=int)
# Named (optional) arguments
parser.add_argument(
'--delete',
action='store_true',
dest='delete',
default=False,
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.
By default, the 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
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 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:
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).Information on how to test custom management commands can be found in the testing docs.
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.
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.
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.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 django.contrib.auth permissions) as
activating any locale might cause unintended effects. See the Management
commands and locales section above for further details.
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.
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(Command, self).__init__(*args, **kwargs)
# ...
BaseCommand.add_arguments(parser)[source]¶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()[source]¶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)[source]¶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)[source]¶The actual logic of the command. Subclasses must implement this method.
It may return a Unicode 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)[source]¶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¶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.
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.
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.
Jun 14, 2020