Async Python Patterns

asyncio and async/await patterns for Python applications.

Quick Start

import asyncio

async def main(): print("Hello") await asyncio.sleep(1) print("World")

asyncio.run(main())

When To Use

• Building async web APIs (FastAPI, aiohttp)

• Implementing concurrent I/O operations

• Creating web scrapers with concurrent requests

• Developing real-time applications (WebSockets)

• Processing multiple independent tasks simultaneously

• Building microservices with async communication

When NOT To Use

• CPU-bound optimization - use python-performance instead

• Testing async code - use python-testing async module

Modules

This skill uses progressive loading. Content is organized into focused modules:

• See modules/basic-patterns.md

• Core async/await, gather(), and task management

• See modules/concurrency-control.md

• Semaphores and locks for rate limiting

• See modules/error-handling-timeouts.md

• Error handling, timeouts, and cancellation

• See modules/advanced-patterns.md

• Context managers, iterators, producer-consumer

• See modules/testing-async.md

• Testing with pytest-asyncio

• See modules/real-world-applications.md

• Web scraping and database operations

• See modules/pitfalls-best-practices.md

• Common mistakes and best practices

Load specific modules based on your needs, or reference all for detailed guidance.

Exit Criteria

• Async patterns applied correctly

• No blocking operations in async code

• Proper error handling implemented

• Rate limiting configured where needed

• Tests pass with pytest-asyncio

Troubleshooting

Common Issues

RuntimeError: no current event loop Use asyncio.run() as the entry point. Avoid get_event_loop() in Python 3.10+.

Blocking call in async context Move sync I/O to asyncio.to_thread() or loop.run_in_executor() .

Tests hang indefinitely Ensure pytest-asyncio is installed and test functions are decorated with @pytest.mark.asyncio .