Python asyncio 收集字典

Question

所以我了解如何通过列表创建异步任务集合并使用 asyncio.gather() 来执行它们，但我不知道如何使用字典执行相同的操作:

    from fastapi import FastAPI
    import asyncio
    import httpx

    app = FastAPI()

    urls = [
        "http://www.google.com",
        "https://www.example.org",
        "https://stackoverflow.com/",
        "https://www.wikipedio.org"
    ]

    async def async_request_return_dict(url: str):
        async with httpx.AsyncClient() as client:
            r = await client.get(url)
        return {url : r.status_code}

    # List of async coroutines
    @app.get("/async_list")
    async def async_list():

        tasks = []
        for url in urls:
            tasks.append(async_request_return_dict(url=url))
        response = await asyncio.gather(*tasks)

        # Convert list of dict -> dict
        dict_response = dict()
        for url in response:
            dict_response.update(url)

        return dict_response

    async def async_request_return_status(url: str):
        async with httpx.AsyncClient() as client:
            r = await client.get(url)
        return r.status_code

    # Dict of async coroutines
    @app.get("/async_dict")
    async def async_dict():

        tasks = dict()
        for url in urls:
            tasks[url] = async_request_return_status(url=url)

        ### How do you run async co-routines inside a dict??? ###
        await asyncio.gather(*tasks.values())
        
        print(tasks)

        return tasks    

/async_list 的输出:

    {
        "http://www.google.com":200,
        "https://www.example.org":200,
        "https://stackoverflow.com/":200,
        "https://www.wikipedio.org":200
    }

/async_dict 的回溯:

INFO:     Application startup complete.
{'http://www.google.com': <coroutine object async_request_return_status at 0x7fec83ded6c0>, 'https://www.example.org': <coroutine object async_request_return_status at 0x7fec83ded740>, 'https://stackoverflow.com/': <coroutine object async_request_return_status at 0x7fec83ded7c0>, 'https://www.wikipedio.org': <coroutine object async_request_return_status at 0x7fec83ded840>}
INFO:     127.0.0.1:58350 - "GET /async_dict HTTP/1.1" 500 Internal Server Error
ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/uvicorn/protocols/http/h11_impl.py", line 396, in run_asgi
    result = await app(self.scope, self.receive, self.send)
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/uvicorn/middleware/proxy_headers.py", line 45, in __call__
    return await self.app(scope, receive, send)
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/fastapi/applications.py", line 199, in __call__
    await super().__call__(scope, receive, send)
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/starlette/applications.py", line 111, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/starlette/middleware/errors.py", line 181, in __call__
    raise exc from None
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/starlette/middleware/errors.py", line 159, in __call__
    await self.app(scope, receive, _send)
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/starlette/exceptions.py", line 82, in __call__
    raise exc from None
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/starlette/exceptions.py", line 71, in __call__
    await self.app(scope, receive, sender)
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/starlette/routing.py", line 566, in __call__
    await route.handle(scope, receive, send)
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/starlette/routing.py", line 227, in handle
    await self.app(scope, receive, send)
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/starlette/routing.py", line 41, in app
    response = await func(request)
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/fastapi/routing.py", line 209, in app
    response_data = await serialize_response(
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/fastapi/routing.py", line 137, in serialize_response
    return jsonable_encoder(response_content)
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/fastapi/encoders.py", line 90, in jsonable_encoder
    encoded_value = jsonable_encoder(
  File "/home/cmaggio/repos/async_dict/.venv/lib/python3.8/site-packages/fastapi/encoders.py", line 141, in jsonable_encoder
    raise ValueError(errors)
ValueError: [TypeError("'coroutine' object is not iterable"), TypeError('vars() argument must have __dict__ attribute')]

基本上如何使用字典执行 asyncio.gather()。或者是在列表中执行协程并在解析所有可等待对象后重新构建字典的第一种方法。

Answer 1

这不会像您预期的那样工作，因为您的字典值是协程，但实际结果值是从 asyncio.gather 返回的。

asyncio.gather :

The order of result values corresponds to the order of awaitables inaws.

基于这个事实你可以这样做:

测试.py:

import asyncio

import httpx


URLS = (
    "http://www.google.com",
    "https://www.example.org",
    "https://stackoverflow.com/",
    "https://www.wikipedio.org",
)


async def req(url):
    async with httpx.AsyncClient() as client:
        r = await client.get(url)

    return r.status_code


async def main():
    tasks = []

    for url in URLS:
        tasks.append(asyncio.create_task(req(url)))

    results = await asyncio.gather(*tasks)

    print(dict(zip(URLS, results)))


if __name__ == "__main__":
    asyncio.run(main())

测试:

$ python test.py
{'http://www.google.com': 200, 'https://www.example.org': 200, 'https://stackoverflow.com/': 200, 'https://www.wikipedio.org': 200}