16. Short Q&A Prompts

Practice prompts to sharpen depth and articulation under time pressure.

• Describe the iterator protocol and how a generator satisfies it. When would you use yield from?

• Show a context manager built with @contextmanager and contrast with a class-based CM.

• Write a small decorator that preserves metadata with functools.wraps.

• Explain dataclass(slots=True, frozen=True) trade-offs.

• Demonstrate match/case with a mapping pattern and a guard (if ...).

• Pick between threads, processes, and asyncio for a given workload and justify.

• Avoid N+1 in SQLAlchemy: selectinload vs joinedload — when each?

• pytest fixtures: scope and parametrization examples.

• Design idempotent POST with Idempotency-Key.

• Prevent a cache stampede: outline lock/jitter/refresh-ahead.

• Show asyncio.Semaphore to cap concurrency.

• Implement optimistic locking with a version column.

• Use pytest monkeypatch to override an env var.

• Explain ExceptionGroup and handle with except*.

• Add ETag-based conditional GET to a REST endpoint.