python 无法使用 HTTP 请求从异步函数中获取 return 值

Question

我正在尝试将我的 Flask 应用程序重写为使用 uvloop 作为基础的 FastAPI。当我在没有路由的情况下执行代码时，我没有发现任何问题并按预期执行。但是在我添加路由并使用 Postman 发出请求后抛出错误。

> INFO: ('172.17.0.1', 42352) - "GET /api/v1/getpass HTTP/1.1" 500
> ERROR: Exception in ASGI application Traceback (most recent call
> last):   File
> "/usr/local/lib/python3.6/site-packages/uvicorn/protocols/http/httptools_impl.py",
> line 375, in run_asgi
>     result = await app(self.scope, self.receive, self.send)   File "/usr/local/lib/python3.6/site-packages/starlette/applications.py",
> line 133, in __call__
>     await self.error_middleware(scope, receive, send)   File "/usr/local/lib/python3.6/site-packages/starlette/middleware/errors.py",
> line 177, in __call__
>     raise exc from None   File "/usr/local/lib/python3.6/site-packages/starlette/middleware/errors.py",
> line 155, in __call__
>     await self.app(scope, receive, _send)   File "/usr/local/lib/python3.6/site-packages/starlette/exceptions.py", line
> 73, in __call__
>     raise exc from None   File "/usr/local/lib/python3.6/site-packages/starlette/exceptions.py", line
> 62, in __call__
>     await self.app(scope, receive, sender)   File "/usr/local/lib/python3.6/site-packages/starlette/routing.py", line
> 590, in __call__
>     await route(scope, receive, send)   File "/usr/local/lib/python3.6/site-packages/starlette/routing.py", line
> 208, in __call__
>     await self.app(scope, receive, send)   File "/usr/local/lib/python3.6/site-packages/starlette/routing.py", line
> 41, in app
>     response = await func(request)   File "/usr/local/lib/python3.6/site-packages/fastapi/routing.py", line 111,
> in app
>     raw_response = await dependant.call(**values)   File "./iowait.py", line 51, in get_pvt
>     print(kpair) UnboundLocalError: local variable 'kpair' referenced before assignment

我的代码：

import random
import asyncio as aio

from fastapi import FastAPI
from pydantic import BaseModel


get_id = '/api/v1/getid'
get_pass = '/api/v1/getpass'
app = FastAPI()
key_pass_list = [
    {
        'uid' : 'uid1',
        'pass' : 'pass1'
    },
    {
        'uid' : 'uid2',
        'pass' : 'pass2'
    },
    {
        'uid' : 'uid3',
        'pass' : 'pass3'
    },
]
id_list = [_['uid'] for _ in key_pass_list]


class KeyDoc(BaseModel):
    uid : str


async def key_pass(uid):
    for keypair in key_pass_list:
        if keypair['uid'] == uid:
            return keypair
    return {uid: 'Key not Found'}


@app.get(get_pass)
async def get_pvt(key_doc: KeyDoc):
    uid = key_doc.uid
    print('uid :' + uid)

    try:
        myloop = aio.get_event_loop()
        kpair = myloop.run_until_complete(aio.wait([key_pass(uid)]))
        await kpair
    except Exception as err:
        print(err)

    print(kpair)
    return None


@app.get(get_id)
async def get_pub():
    return random.choice(id_list)


@app.get("/")
async def root():
    return {"message": "Test-AIO"}

注意
get_id 和 / 路由随时可用，因为没有逻辑，它因 get_pass 请求而失败。
非常感谢对此的任何帮助或指示。
谢谢

Answer 1

这里有两件事。首先，使用 aio.get_event_loop() 会在 await kpair 之前抛出异常 This event loop is already running，这会抛出您在尝试打印不存在的变量时看到的 UnboundLocalError。您可以通过在 get_pvt 中的第一个打印语句下添加 kpair = None 来查看此行为。以下是您将如何使用 asyncio.wait.

构建此结构

@app.get(get_pass)
async def get_pvt(key_doc: KeyDoc):
    uid = key_doc.uid
    print('uid :' + uid)
    done = set()
    try:
        done, pending = await aio.wait([key_pass(uid)])
    except Exception as err:
        print(err)

    if done:
        for task in done:
            print(task.result())
    return None

python 无法使用 HTTP 请求从异步函数中获取 return 值

python Unable to get return values from async function using HTTP requests

python

python-asyncio

uvloop

fastapi