Teardown hooks in Flask - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a teardown hook in Flask?

A teardown hook in Flask is a function that runs after each request, used to clean up resources like closing database connections.

beginner

How do you register a teardown hook in Flask?

You register a teardown hook using the @app.teardown_appcontext decorator for app-level cleanup or @app.teardown_request for request-level cleanup.

intermediate

When exactly does a teardown hook run in Flask?

A teardown hook runs after the response is sent to the client, regardless of whether the request was successful or raised an error.

intermediate

What argument does a teardown function receive in Flask?

A teardown function receives an error argument that is None if no error occurred, or contains the exception if one happened during the request.

beginner

Why are teardown hooks important in Flask applications?

Teardown hooks help prevent resource leaks by ensuring things like database connections or files are properly closed after each request.

Which decorator is used to register a teardown hook for the entire Flask application context?

A @app.route

B @app.teardown_appcontext

C @app.before_request

D @app.after_request

The @app.teardown_appcontext decorator registers a function to run when the application context tears down.

When does a teardown hook run in Flask?

A After the response is sent

B Only if the request is successful

C Only if the request raises an error

D Before the request starts

Teardown hooks run after the response is sent, regardless of success or error.

What argument does a teardown function receive?

A An error object or None

B The response object

C The request object

D No arguments

Teardown functions receive an error argument that is None if no error occurred.

Which of these is a common use for teardown hooks?

A Starting a database connection

B Logging request start time

C Closing database connections

D Rendering templates

Teardown hooks are commonly used to close database connections or clean up resources.

Can teardown hooks modify the response sent to the client?

A Only if an error occurred

B Yes, always

C Only if no error occurred

D No, they run after response is sent

Teardown hooks run after the response is sent, so they cannot modify it.

Explain what a teardown hook is in Flask and why it is useful.

Think about what happens after a web request finishes.

Describe how to register a teardown hook in Flask and what argument the function receives.

Focus on the decorator and function signature.