Writing custom 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/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
_private.py module will not be available as a management command.
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))
Before Django 1.8, management commands were based on the
optparse module, and positional arguments were passed in
*args while optional arguments were passed in
**options. Now that management commands use
argparse for argument parsing, all arguments are passed in
**options by default, unless you name your positional arguments to
args (compatibility mode). You are encouraged to exclusively use
**options for new commands.
When you are using management commands and wish to provide console output, you should write to
self.stderr, instead of printing to
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
self.stdout.write("Unterminated line", ending='')
The new custom command can be called using
python manage.py closepoll
handle() method takes one or more
poll_ids and sets
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.
Accepting optional arguments
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() # ...
Previously, only the standard
optparse library was supported and you would have to extend the command
option_list variable with
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
Management commands and locales
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.
In previous versions, Django forced the “en-us” locale instead of deactivating translations.
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): ... can_import_settings = True 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
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
USE_I18Nsetting is always
Truewhen 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.
Information on how to test custom management commands can be found in the testing docs.
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.
A string listing the arguments accepted by the command, suitable for use in help messages; e.g., a command which takes a list of application names might set this to ‘<app_label app_label ...>’.
Deprecated since version 1.8: This should be done now in the
add_arguments()method, by calling the
parser.add_argument()method. See the
A boolean indicating whether the command needs to be able to import Django settings; if
execute()will verify that this is possible before proceeding. Default value is
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>.
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”).
This is the list of
optparseoptions which will be fed into the command’s
OptionParserfor parsing arguments.
A boolean indicating whether the command outputs SQL statements; if
True, the output will automatically be wrapped with
COMMIT;. Default value is
A boolean; if
True, the entire Django project will be checked for potential problems prior to executing the command. Default value is
A boolean indicating whether the locale set in settings should be preserved during the execution of the command instead of being forcibly set to ‘en-us’.
Default value is
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 making the locale differ from the de facto default ‘en-us’ might cause unintended effects. Seethe Management commands and locales section above for further details.
An instance attribute that helps create colored output when writing to
stderr. For example:
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-coloroption when running your command, all
self.style()calls will return the original string uncolored.
Implementing a constructor in a subclass
class Command(BaseCommand): def __init__(self, *args, **kwargs): super(Command, self).__init__(*args, **kwargs) # ...
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
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.
Tries to execute this command, performing system checks if needed (as controlled by the
requires_system_checksattribute). 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
The actual logic of the command. Subclasses must implement this method.
It may return a Unicode string which will be printed to
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.
None, all system checks are performed.
tagscan be a list of check tags, like
A management command which takes one or more installed application labels as arguments, and does something with each of them.
Perform the command’s actions for
app_config, which will be an
AppConfiginstance corresponding to an application label given on the command line.
A management command which takes one or more arbitrary arguments (labels) on the command line, and does something with each of them.
Perform the command’s actions for
label, which will be the string as given on the command line.
Deprecated since version 1.8: Use
BaseCommand instead, which takes no arguments by default.
A command which takes no arguments on the command line.
Perform this command’s actions
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.
© Django Software Foundation and individual contributors
Licensed under the BSD License.