Question 1

How do I structure concurrent asyncio tasks in Python?

Accepted Answer

Use asyncio.TaskGroup to manage child-task lifetimes and get grouped failure propagation automatically. Bound fan-out with a semaphore, queue, or worker pool instead of creating unbounded tasks, especially from untrusted input.

Question 2

When should I use asyncio vs threads vs processes in Python?

Accepted Answer

Use asyncio for many cooperating I/O operations with async-aware libraries, threads for blocking I/O that cannot be made async, and processes or interpreters for CPU-bound work. Prefer synchronous code when concurrency adds no material benefit.

Question 3

How do I handle cancellation in asyncio correctly?

Accepted Answer

Let CancelledError propagate by default. Catch it only when cleanup is necessary, perform the cleanup, then re-raise it so the cancellation contract is preserved and tasks terminate properly.

Question 4

Why does my async Python code hang or block the event loop?

Accepted Answer

Blocking calls on the event-loop thread freeze all concurrent tasks. Offload unavoidable blocking calls explicitly, and add asyncio.timeout at meaningful operation boundaries so stuck operations fail instead of hanging silently.

Question 5

How should I handle exceptions from multiple asyncio tasks?

Accepted Answer

Define upfront whether one failure cancels siblings, gets collected, or is retried. Handle ExceptionGroup only at a boundary that can make that policy decision, and test partial failure, timeout, and cancellation paths.

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