signals and built in signals in django

Django provides a feature called signals that allow certain senders to notify a set of receivers about some action that has taken place. Signals are used to allow decoupled applications to get notified when certain actions occur elsewhere in the application. This can be useful when multiple applications need to perform certain actions in response to specific events.

Django provides some built-in signals that are fired during the lifecycle of a model instance. These signals allow you to perform certain actions before or after a specific event occurs. Here are some of the built-in signals in Django:

  1. pre_init: This signal is emitted just before a model's init method is called during the process of creating a new instance of the model.

  2. post_init: This signal is emitted just after a model's init method is called during the process of creating a new instance of the model.

  3. pre_save: This signal is emitted just before a model's save() method is called. It can be used to perform certain actions or modifications on the model instance before it is saved to the database.

  4. post_save: This signal is emitted just after a model's save() method is called. It can be used to perform certain actions or updates on the model instance after it has been saved to the database.

  5. pre_delete: This signal is emitted just before a model's delete() method is called. It can be used to perform certain actions or checks before a model instance is deleted from the database.

  6. post_delete: This signal is emitted just after a model's delete() method is called. It can be used to perform certain actions or updates after a model instance has been deleted from the database.

These signals can be connected to receiver functions using the @receiver decorator or the connect() method. Receiver functions are functions that are executed when the signal is emitted. They can perform any desired actions based on the signal event.

By using signals in Django, you can achieve a decoupled and flexible architecture, where different parts of your application can react to specific events without tightly coupling them together.