async-python-patterns

Concurrent I/O operations use asyncio to execute multiple tasks like HTTP requests or database queries simultaneously. AsyncIO allows tasks to yield control while waiting, enabling near-linear scaling for I/O-bound workloads without threading overhead.

FastAPI supports async endpoints natively, allowing you to define coroutine handlers that process concurrent requests efficiently. Async endpoints scale I/O-bound operations by freeing worker threads while awaiting external services.

Asyncio semaphores control concurrency by limiting the number of tasks running simultaneously. Combined with asyncio.gather, semaphores enforce rate limits while executing parallel API calls, preventing overwhelming downstream services.

Asyncio.gather accepts a return_exceptions parameter to capture exceptions from individual coroutines without halting others. This enables robust error handling across concurrent I/O operations, allowing partial results and logging of failures.

Aiohttp is an async HTTP client that integrates seamlessly with asyncio, enabling non-blocking HTTP requests across multiple URLs. It replaces blocking requests libraries in async workflows, maximizing concurrency for web scraping and API integration.

Async patterns outperform threading for I/O-bound workloads by eliminating context-switch overhead and simplifying concurrent code. Use asyncio when coordinating many simultaneous I/O operations like database queries or HTTP calls within a single process.