Python interview questions and answers

Dunder methods, also called magic methods, are special names with double underscores such as __init__ and __str__.

__str__ returns the informal string used by str() and print().

__len__ is called by len() and should return a non-negative int.

__eq__ implements == for your class.

unittest is the standard library's xUnit-style test framework.

pytest is a third-party runner with plain assert, fixtures, and rich plugins.

django.test.TestCase wraps each test in a database transaction that is rolled back.

View tests catch broken URLs, auth, status codes, and template context before production.

Middleware is a hook that runs on every request and response.

The MIDDLEWARE list in settings.py is an ordered sequence of dotted class paths.

SecurityMiddleware sets HTTPS redirects and security headers such as HSTS.

Signals are a dispatcher that lets decoupled apps react to events such as a model save.

post_save runs after a model is saved to the database.

Decorate a function with @receiver(post_save, sender=MyModel) or call post_save.connect(handler, sender=MyModel).

DRF is a toolkit for building Web APIs on top of Django.

A serializer converts model instances or primitives to JSON-like data and validates incoming payloads.

APIView is DRF's base class-based view.

@api_view turns a function into a DRF function-based view and lists allowed methods.

Caching stores expensive query or render results so later requests skip the work.

django.core.cache.cache.set(key, value, timeout) stores a pickled value in the configured backend.