A list of all the signals that Django sends.
See also
See the documentation on the signal dispatcher for information regarding how to register for and receive signals.
The authentication framework sends signals when a user is logged in / out.
The django.db.models.signals module defines a set of signals sent by the model system.
Warning
Many of these signals are sent by various model methods like __init__() or save() that you can override in your own code.
If you override these methods on your model, you must call the parent class’ methods for this signals to be sent.
Note also that Django stores signal handlers as weak references by default, so if your handler is a local function, it may be garbage collected. To prevent this, pass weak=False when you call the signal’s connect().
Model signals sender model can be lazily referenced when connecting a receiver by specifying its full application label. For example, an Answer model defined in the polls application could be referenced as 'polls.Answer'. This sort of reference can be quite handy when dealing with circular import dependencies and swappable models.
Whenever you instantiate a Django model, this signal is sent at the beginning of the model’s __init__() method.
Arguments sent with this signal:
For example, the tutorial has this line:
p = Poll(question="What's up?", pub_date=datetime.now())
The arguments sent to a pre_init handler would be:
| Argument | Value |
|---|---|
| sender | Poll (the class itself) |
| args | [] (an empty list because there were no positional arguments passed to __init__().) |
| kwargs | {'question': "What's up?", 'pub_date': datetime.now()} |
Like pre_init, but this one is sent when the __init__() method finishes.
Arguments sent with this signal:
This is sent at the beginning of a model’s save() method.
Arguments sent with this signal:
Like pre_save, but sent at the end of the save() method.
Arguments sent with this signal:
Sent at the beginning of a model’s delete() method and a queryset’s delete() method.
Arguments sent with this signal:
Like pre_delete, but sent at the end of a model’s delete() method and a queryset’s delete() method.
Arguments sent with this signal:
The actual instance being deleted.
Note that the object will no longer be in the database, so be very careful what you do with this instance.
Sent when a ManyToManyField is changed on a model instance. Strictly speaking, this is not a model signal since it is sent by the ManyToManyField, but since it complements the pre_save/post_save and pre_delete/post_delete when it comes to tracking changes to models, it is included here.
Arguments sent with this signal:
A string indicating the type of update that is done on the relation. This can be one of the following:
For the pre_add, post_add, pre_remove and post_remove actions, this is a set of primary key values that have been added to or removed from the relation.
For the pre_clear and post_clear actions, this is None.
For example, if a Pizza can have multiple Topping objects, modeled like this:
class Topping(models.Model):
# ...
pass
class Pizza(models.Model):
# ...
toppings = models.ManyToManyField(Topping)
If we connected a handler like this:
from django.db.models.signals import m2m_changed
def toppings_changed(sender, **kwargs):
# Do something
pass
m2m_changed.connect(toppings_changed, sender=Pizza.toppings.through)
and then did something like this:
>>> p = Pizza.objects.create(...)
>>> t = Topping.objects.create(...)
>>> p.toppings.add(t)
the arguments sent to a m2m_changed handler (toppings_changed in the example above) would be:
| Argument | Value |
|---|---|
| sender | Pizza.toppings.through (the intermediate m2m class) |
| instance | p (the Pizza instance being modified) |
| action | "pre_add" (followed by a separate signal with "post_add") |
| reverse | False (Pizza contains the ManyToManyField, so this call modifies the forward relation) |
| model | Topping (the class of the objects added to the Pizza) |
| pk_set | {t.id} (since only Topping t was added to the relation) |
| using | "default" (since the default router sends writes here) |
And if we would then do something like this:
>>> t.pizza_set.remove(p)
the arguments sent to a m2m_changed handler would be:
| Argument | Value |
|---|---|
| sender | Pizza.toppings.through (the intermediate m2m class) |
| instance | t (the Topping instance being modified) |
| action | "pre_remove" (followed by a separate signal with "post_remove") |
| reverse | True (Pizza contains the ManyToManyField, so this call modifies the reverse relation) |
| model | Pizza (the class of the objects removed from the Topping) |
| pk_set | {p.id} (since only Pizza p was removed from the relation) |
| using | "default" (since the default router sends writes here) |
Sent whenever a model class has been “prepared” – that is, once model has been defined and registered with Django’s model system. Django uses this signal internally; it’s not generally used in third-party applications.
Since this signal is sent during the app registry population process, and AppConfig.ready() runs after the app registry is fully populated, receivers cannot be connected in that method. One possibility is to connect them AppConfig.__init__() instead, taking care not to import models or trigger calls to the app registry.
Arguments that are sent with this signal:
Signals sent by django-admin.
Sent by the migrate command before it starts to install an application. It’s not emitted for applications that lack a models module.
Arguments sent with this signal:
Indicates how much information manage.py is printing on screen. See the --verbosity flag for details.
Functions which listen for pre_migrate should adjust what they output to the screen based on the value of this argument.
If interactive is True, it’s safe to prompt the user to input things on the command line. If interactive is False, functions which listen for this signal should not try to prompt for anything.
For example, the django.contrib.auth app only prompts to create a superuser when interactive is True.
Deprecated since version 1.7: This signal has been replaced by pre_migrate.
Sent by the syncdb command before it starts to install an application.
Arguments sent with this signal:
Indicates how much information manage.py is printing on screen. See the --verbosity flag for details.
Functions which listen for pre_syncdb should adjust what they output to the screen based on the value of this argument.
If interactive is True, it’s safe to prompt the user to input things on the command line. If interactive is False, functions which listen for this signal should not try to prompt for anything.
For example, the django.contrib.auth app only prompts to create a superuser when interactive is True.
Sent by the migrate command after it installs an application, and the flush command. It’s not emitted for applications that lack a models module.
It is important that handlers of this signal perform idempotent changes (e.g. no database alterations) as this may cause the flush management command to fail if it also ran during the migrate command.
Arguments sent with this signal:
Indicates how much information manage.py is printing on screen. See the --verbosity flag for details.
Functions which listen for post_migrate should adjust what they output to the screen based on the value of this argument.
If interactive is True, it’s safe to prompt the user to input things on the command line. If interactive is False, functions which listen for this signal should not try to prompt for anything.
For example, the django.contrib.auth app only prompts to create a superuser when interactive is True.
For example, you could register a callback in an AppConfig like this:
from django.apps import AppConfig
from django.db.models.signals import post_migrate
def my_callback(sender, **kwargs):
# Your specific logic here
pass
class MyAppConfig(AppConfig):
...
def ready(self):
post_migrate.connect(my_callback, sender=self)
Note
If you provide an AppConfig instance as the sender argument, please ensure that the signal is registered in ready(). AppConfigs are recreated for tests that run with a modified set of INSTALLED_APPS (such as when settings are overridden) and such signals should be connected for each new AppConfig instance.
Deprecated since version 1.7: This signal has been replaced by post_migrate.
Sent by the syncdb command after it installs an application, and the flush command.
It is important that handlers of this signal perform idempotent changes (e.g. no database alterations) as this may cause the flush management command to fail if it also ran during the syncdb command.
Arguments sent with this signal:
Indicates how much information manage.py is printing on screen. See the --verbosity flag for details.
Functions which listen for post_syncdb should adjust what they output to the screen based on the value of this argument.
If interactive is True, it’s safe to prompt the user to input things on the command line. If interactive is False, functions which listen for this signal should not try to prompt for anything.
For example, the django.contrib.auth app only prompts to create a superuser when interactive is True.
For example, yourapp/management/__init__.py could be written like:
from django.db.models.signals import post_syncdb
import yourapp.models
def my_callback(sender, **kwargs):
# Your specific logic here
pass
post_syncdb.connect(my_callback, sender=yourapp.models)
Signals sent by the core framework when processing a request.
Sent when Django begins processing an HTTP request.
Arguments sent with this signal:
The environ argument was added.
Sent when Django finishes delivering an HTTP response to the client.
Note
Some WSGI servers and middleware do not always call close on the response object after handling a request, most notably uWSGI prior to 1.2.6 and Sentry’s error reporting middleware up to 2.0.7. In those cases this signal isn’t sent at all. This can result in idle connections to database and memcache servers.
Arguments sent with this signal:
This signal is sent whenever Django encounters an exception while processing an incoming HTTP request.
Arguments sent with this signal:
Signals only sent when running tests.
This signal is sent when the value of a setting is changed through the django.test.TestCase.settings() context manager or the django.test.override_settings() decorator/context manager.
It’s actually sent twice: when the new value is applied (“setup”) and when the original value is restored (“teardown”). Use the enter argument to distinguish between the two.
You can also import this signal from django.core.signals to avoid importing from django.test in non-test situations.
The signal was moved to django.core.signals as described above.
Arguments sent with this signal:
A boolean; True if the setting is applied, False if restored.
Signals sent by the database wrapper when a database connection is initiated.
Sent when the database wrapper makes the initial connection to the database. This is particularly useful if you’d like to send any post connection commands to the SQL backend.
Arguments sent with this signal:
May 13, 2015