Python interview questions and answers

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.

Each object has a refcount

Cycles delay reclamation until GC runs, which can retain large graphs longer than you expect.

A list holds every element at once.

__repr__ should be unambiguous and, if practical, look like a constructor call for debugging.

__enter__ runs at the start of a with block and its return value is bound to as.

__getitem__ implements indexing and slicing, and if it raises IndexError, for-loops can treat the object as a sequence.

groupby clusters consecutive items that share a key function's result.

chain concatenates iterables without building an intermediate list, useful when merging query results you already have as iterators.

yield produces iterator values and pauses a generator.

The loop schedules ready callbacks and coroutines, waits on sockets, and resumes them when I/O completes.