pre_save and post_save signals in Django - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the pre_save signal in Django?

The pre_save signal is sent just before a model's save() method is called. It allows you to run code or modify data before the object is saved to the database.

beginner

When is the post_save signal triggered in Django?

The post_save signal is triggered immediately after a model instance has been saved to the database. It is useful for actions that depend on the object being saved.

intermediate

How do you connect a function to the pre_save signal for a Django model?

You use the @receiver(pre_save, sender=YourModel) decorator or pre_save.connect(your_function, sender=YourModel) to link your function to the signal.

intermediate

What arguments does a signal handler for post_save receive?

A post_save handler receives sender, instance (the saved object), created (True if new object), update_fields, and kwargs.

advanced

Why might you use pre_save instead of overriding the save() method?

Using pre_save keeps your code separate from the model logic, making it easier to maintain and reuse. It also allows multiple functions to listen to the save event without changing the model.

Which signal is sent before a Django model instance is saved?

A pre_delete

B pre_save

C post_save

D post_delete

The pre_save signal is sent just before saving a model instance.

What does the created argument in a post_save signal handler indicate?

A If the instance was updated

B If the save was successful

C If the instance was deleted

D If the instance was newly created

The created argument is True if the instance was created, False if updated.

How can you connect a function to a Django signal?

A By overriding the model's <code>save()</code> method

B By importing the signal in views.py

C Using <code>@receiver</code> decorator or <code>signal.connect()</code>

D By calling the function manually

You connect signal handlers using the @receiver decorator or the connect() method.

Which signal would you use to perform an action after a model instance is saved?

A post_save

B pre_save

C pre_delete

D post_init

The post_save signal runs after the instance is saved.

What is a benefit of using Django signals like pre_save and post_save?

A They allow decoupled code to react to model events

B They automatically create admin pages

C They speed up database queries

D They replace the need for models

Signals let different parts of your app respond to events without tightly coupling code.

Explain how pre_save and post_save signals work in Django and when you might use each.

Think about what happens before and after saving a model.

Describe how to connect a function to a Django model's post_save signal and what arguments the function receives.

Focus on the connection method and handler parameters.