Python interview questions and answers

By default Django stores receivers as weak references, so a local function can be garbage-collected and silently stop running.

Avoid them for core business rules that callers must understand

ModelSerializer maps model fields quickly and is enough for straightforward CRUD.

GenericAPIView plus mixins gives you get/post handlers and queryset/serializer_class.

DefaultRouter and SimpleRouter bind viewset actions to URL patterns including optional trailing slashes.

Authentication identifies the user (who is calling) and sets request.user and request.auth.

Pagination classes split list querysets into pages and add next/previous metadata.

Nest a serializer as a field, or use depth on ModelSerializer for read-only trees.

The broker (Redis, RabbitMQ) transports task messages to workers.

delay(*args, **kwargs) is a shortcut for apply_async.

Bind the task with bind=True and call self.retry(exc=exc, countdown=seconds) inside the catch block, or set autoretry_for and retry_backoff.

Beat is a scheduler that enqueues periodic tasks according to a schedule in code or the database.

Per-view cache (@cache_page) stores the whole response, which is best for anonymous pages that are identical for everyone.

Include a version or key prefix, the resource id, and any vary dimension such as locale.

LocMemCache is per-process and wrong for multi-worker production because each Gunicorn worker has its own dict.

cached_property memoizes on the instance for the lifetime of that Python object, with no network hop.

Client runs the full stack: URL routing, middleware, sessions, and templates.

JSON/YAML fixtures load static rows but are brittle as models evolve.

assertNumQueries(n) on TestCase fails when the count drifts.

Patch the client function with unittest.mock or use responses/httpx mock to return canned JSON.