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
command for the
polls application from the
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
look like this:
from django.core.management.base import BaseCommand, CommandError from polls.models import Poll class Command(BaseCommand): args = '<poll_id poll_id ...>' help = 'Closes the specified poll for voting' def handle(self, *args, **options): for poll_id in args: try: poll = Poll.objects.get(pk=int(poll_id)) except Poll.DoesNotExist: raise CommandError('Poll "%s" does not exist' % poll_id) poll.opened = False poll.save() self.stdout.write('Successfully closed poll "%s"' % poll_id)
When you are using management commands and wish to provide console
output, you should write to
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 zero 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.Poll for this example.
closepoll could be easily modified to delete a given poll instead
of closing it by accepting additional command line options. These custom options
must be added to
option_list like this:
from optparse import make_option class Command(BaseCommand): option_list = BaseCommand.option_list + ( make_option('--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
optparse Python documentation
for more about
Management commands and locales¶
By default, the
BaseCommand.execute() method sets the hardcoded ‘en-us’
locale because some commands shipped with Django perform several tasks
(for example, user-facing content rendering and database population) that
require a system-neutral string language (for which we use ‘en-us’).
If, for some reason, your custom management command needs to use a fixed locale
different from ‘en-us’, you should manually activate and deactivate it in your
handle_noargs() 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 forcing it to ‘en-us’. 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 always using a fixed locale).
- 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.
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 ...>’.
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>.
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. If
requires_system_checks is missing, the value of
requires_model_validation is used. If the latter flag is missing
as well, the default value (
True) is used. Defining both
requires_model_validation will result
in an error.
Deprecated since version 1.7: Replaced by
A boolean; if
True, validation of installed models will be
performed prior to executing the command. Default value is
True. To validate an individual application’s models
rather than all applications’ models, call
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. See the Management commands and locales section above for further details.
leave_locale_alone option was added in Django 1.6.
Implementing a constructor in a subclass
class Command(BaseCommand): def __init__(self, *args, **kwargs): super(Command, self).__init__(*args, **kwargs) # ...
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 call_command instead.
The actual logic of the command. Subclasses must implement this method.
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
warnings are output to stderr; minor notifications are output to stdout.
tags are both
None, all system checks are
tags can be a list of check tags, like
Deprecated since version 1.7: Replaced with the
app is None, then all installed apps are checked for errors.
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.
AppCommand subclasses had to implement
handle_app(app, **options) where
app was a models module. The new
API makes it possible to handle applications without a models module. The
fastest way to migrate is as follows:
def handle_app_config(app_config, **options): if app_config.models_module is None: return # Or raise an exception. app = app_config.models_module # Copy the implementation of handle_app(app_config, **options) here.
However, you may be able to simplify the implementation by using directly
the attributes of
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.
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.