Drills

Architecture scenarioMedium~10 min

When should a pytest fixture return a factory instead of one fixed object?

Uses fixture factories and test-data builders to keep setup flexible, readable, and owned by each test.

pytestPython

Architecture scenarioMedium~10 min

When should a SQLAlchemy API query project columns instead of loading entities?

Aligns selected database data with an API read model and avoids unnecessary ORM state.

PythonSQLAlchemy

Concept questionMedium~10 min

When should Python async code use ContextVar instead of a global or thread-local value?

Uses task-aware context for tracing while keeping business inputs explicit and correctly reset.

When should Python code use secrets and compare_digest instead of random and normal equality?

Uses cryptographically secure token generation and timing-resistant comparison at credential boundaries.

Comparison questionHard~15 min

When should you use a Django signal instead of an explicit function call?

Uses Django signals selectively and makes transaction timing and side effects explicit.

Comparison questionEasy~5 min

When should you use is instead of == in Python?

Distinguishes object identity from value equality and prevents fragile code based on interning or implementation accidents.

When should you use pytest skip, xfail, or quarantine a test?

Distinguishes unavailable conditions, known defects, and unstable tests while keeping lost coverage visible.

pytestPython

Comparison questionMedium~7 min

When would you choose a comprehension or a generator expression in Python?

Compares eager collections with lazy one-pass generation through memory, timing, reuse, readability, and resource ownership.

When would you use a function-based or class-based Django view?

Chooses Django view style by clarity, reuse, and lifecycle needs rather than hierarchy preference.

Comparison questionHard~10 min

When would you use a Protocol instead of an abstract base class in Python?

Chooses structural or nominal contracts based on ownership, runtime identity, shared behavior, and third-party integration.

When would you use asyncio Lock, Event, Condition, or Semaphore?

Chooses task synchronization by protected state, notification predicates, and limited capacity.

Comparison questionHard~15 min

When would you use asyncio.TaskGroup or asyncio.gather()?

Compares structured task ownership with ordered result aggregation and different failure behavior.

Comparison questionHard~15 min

When would you use asyncio.to_thread() or run_in_executor()?

Compares convenient context-propagating thread offload with explicit executor selection and ownership.

When would you use Django select_related or prefetch_related?

Chooses Django relationship loading from relationship shape, result cardinality, and measured query behavior.

When would you use FastAPI TestClient versus an async HTTP client?

Chooses synchronous or asynchronous FastAPI test clients from the boundary exercised and resources involved.

FastAPIpytestPython

When would you use SQLAlchemy ORM, SQLAlchemy Core, or raw SQL?

Chooses a SQLAlchemy abstraction from the work's shape instead of performance slogans.

PythonSQLAlchemy

Architecture scenarioHard~15 min

Where should a SQLAlchemy transaction begin and end, and when are savepoints useful?

Aligns SQLAlchemy transactions with business operations and uses savepoints without inventing independent commits.

PythonSQLAlchemy

Architecture scenarioHard~15 min

Where should business logic live in a Django application?

Balances model methods, QuerySets, managers, and application services by the responsibility they own.

Architecture scenarioHard~10 min

Where should Python backend code catch, translate, or re-raise exceptions?

Places exception handling at meaningful boundaries and preserves causes, tracebacks, client contracts, and retry safety.

Debugging scenarioMedium~7 min

Why can mutable default arguments cause bugs in Python?

Diagnoses shared mutable function defaults and explains safe initialization without turning the behavior into a superstition.

Debugging scenarioHard~15 min

Why does a pytest monkeypatch sometimes have no effect, and where should you patch?

Explains Python name binding and patches the reference actually used by the system under test.

pytestPython

Architecture scenarioHard~15 min

Why does middleware order matter in Django?

Explains Django's nested middleware stack, short-circuiting, exceptions, and response unwinding.

Architecture scenarioHard~10 min

Why does middleware order matter in FastAPI and Starlette?

Explains nested ASGI middleware ordering, reverse response flow, exception boundaries, CORS, and streaming-safe design.

FastAPIPydanticPython