Explain how asyncio works and when you would choose it over threads or processes.
Answer
- One thread, one event loop. Coroutines (
async def) give control back at each await, so the loop can run other tasks while one waits on I/O. - Cooperative: any blocking call (CPU work,
time.sleep, a sync DB driver) freezes everything. - Tools:
asyncio.gather, TaskGroup, create_task, Semaphore to limit concurrency, wait_for for timeouts. - Choose asyncio for many simultaneous I/O operations (thousands of sockets, API fan-out, websockets).
- Threads: simpler for a few blocking calls with sync libraries.
- Processes: CPU-bound work.
- Run blocking code from async with
asyncio.to_thread / run_in_executor.
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