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python-async-concurrency

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Original

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Translation

Chinese

Python Async & Concurrency

Python异步与并发

When to use this skill

何时使用该技能

Writing high-concurrency I/O bound applications (FastAPI, bots, scrapers).
Using
```
asyncio
```
,
```
aiohttp
```
, or
```
httpx
```
.
Managing background tasks or task queues.

编写高并发I/O密集型应用（FastAPI、机器人、爬虫）。
使用
```
asyncio
```
、
```
aiohttp
```
或
```
httpx
```
。
管理后台任务或任务队列。

1. Asyncio Basics

1. Asyncio基础

Entry Point: Use
```
asyncio.run(main())
```
for the entry point.
TaskGroups: Use
```
async with asyncio.TaskGroup() as tg
```
(Python 3.11+) instead of
```
gather()
```
for better error handling/cancellation.
Blocking Code: Run blocking (CPU-bound) code in
```
await asyncio.to_thread(...)
```
.

入口点：使用
```
asyncio.run(main())
```
作为入口。
TaskGroups：使用
```
async with asyncio.TaskGroup() as tg
```
（Python 3.11+）替代
```
gather()
```
，以获得更好的错误处理/取消机制。
阻塞代码：在
```
await asyncio.to_thread(...)
```
中运行阻塞（CPU密集型）代码。

2. HTTP Clients

2. HTTP客户端

HTPX/AIOHTTP: Use
```
httpx.AsyncClient
```
or
```
aiohttp.ClientSession
```
as a context manager.
Singleton: Reuse the client session across requests; do not create a new one per request.

HTPX/AIOHTTP：将
```
httpx.AsyncClient
```
或
```
aiohttp.ClientSession
```
作为上下文管理器使用。
单例模式：在多个请求间复用客户端会话；不要为每个请求创建新的会话。

3. Pitfalls

3. 常见陷阱

Sync in Async: Never call blocking sync functions (requests, time.sleep) inside async functions.
Fire and Forget: Avoid unreferenced background tasks; keep a reference to prevent garbage collection (or use
```
TaskGroup
```
).

异步中调用同步：切勿在异步函数内调用阻塞式同步函数（如requests、time.sleep）。
“即发即弃”任务：避免无引用的后台任务；保留引用以防止被垃圾回收（或使用
```
TaskGroup
```
）。