Django signals

Django signals are a way to allow decoupled applications to get notified when certain actions occur elsewhere in the application. Signals are used to provide a way for different components of an application to communicate with each other without being tightly coupled.

In Django, signals are dispatched by senders and received by receivers. A sender is typically an instance of a particular model class, and a receiver is a function that gets executed whenever the signal is sent. Signals can be created for various events, such as when an object is saved, deleted, or when a user logs in or logs out.

To use signals in Django, you need to define a receiver function and connect it to the appropriate signal. This can be done in the `signals.py` file of your Django app. Here's an example:

from django.db.models.signals import post_save
from django.dispatch import receiver
from myapp.models import MyModel

@receiver(post_save, sender=MyModel)
def my_receiver(sender, instance, created, **kwargs):
    # Do something when MyModel instance is saved
    if created:
        print("A new MyModel instance has been created!")
    else:
        print("A MyModel instance has been updated!")

In this example, the `my_receiver` function is decorated with the `@receiver` decorator, which connects it to the `post_save` signal of the `MyModel` class. The receiver function receives the sender (the `MyModel` class), the instance of the model being saved, and the `created` argument which indicates whether a new instance was created or an existing one was updated.

By connecting receivers to signals, you can perform additional actions or trigger certain behaviors whenever specific events occur in your Django application.