如何使用异步for循环遍历列表? [英] How to use an async for loop to iterate over a list?

问题描述

因此，我需要为列表中的所有项目调用async函数.这可能是URL列表和使用aiohttp的异步函数，该函数从每个URL返回响应.现在显然我不能执行以下操作:

So I need to call an async function for all items in a list. This could be a list of URLs and an async function using aiohttp that gets a response back from every URL. Now obviously I cannot do the following:

async for url in ['www.google.com', 'www.youtube.com', 'www.aol.com']:

我可以使用普通的for循环，但是我的代码将同步运行，并且失去了具有async响应获取功能的好处和速度.

I can use a normal for loop but then my code will act synchronously and I lose the benefits and speed of having an async response fetching function.

有什么办法可以转换列表以使上述工作正常?我只需要将列表的__iter__()更改为__aiter__()方法，对吗?可以通过对列表进行子类化来实现?也许将其封装在一个类中?

Is there any way I can convert a list such that the above works? I just need to change the list's __iter__() to a __aiter__() method right? Can this be achieved by subclassing a list? Maybe encapsulating it in a class?

推荐答案

使用或 asyncio.gather :

results = await asyncio.gather(map(fetch, urls))

---

编辑:如果您不介意具有外部依赖性，则可以使用

---

If you don't mind having an external dependency, you can use aiostream.stream.map:

from aiostream import stream, pipe

async def fetch_many(urls):
    xs = stream.iterate(urls) | pipe.map(fetch, ordered=True, task_limit=10)
    async for result in xs:
        print(result)

您可以使用task_limit参数控制同时运行的fetch协程的数量，并选择是按顺序获取结果还是尽快获取结果.

You can control the amount of fetch coroutine running concurrently using the task_limit argument, and choose whether to get the results in order, or as soon as possible.

在此演示和 _{免责声明:我是项目维护者.}

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