循环内部的Python异步请求调用

Question

我正在尝试用FastAPI开发Python，我必须从几个URL下载一系列图像，放在一个foor循环中。

问题是，我必须检索图像，但我不能这样做，因为它是一个正常的for循环中的异步操作。

这是我的代码：

@app.post("/v1/img_color")
async def img_color(request: Request):
    body = await request.json()
    images = []
    
    for img in body['images']:
        img_id = img['id']
        img_url = img['url']
        r = requests.get(img_url)
        content = await r.content
        dw_image = Image.open(BytesIO(content))
        images.append(dw_image)
    

    return images

但它给了我以下错误：

TypeError:在“等待”表达式中不能使用对象字节

我怎么才能解决这个问题？我已经搜索过这个问题，并找到了一些关于asyncio的解决方案，但我无法让它们发挥作用。

更新：

按照从await中删除await r.content代码的建议，我遇到了另一个错误，即：

TypeError(‘无法将字典更新序列元素#0转换为序列’)，TypeError('vars()参数必须具有dict属性‘)

我不太明白这一点，因为我可以从原始POST请求的JSON正文中完美地检索url .

回溯

Traceback (most recent call last):
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\uvicorn\protocols\http\h11_impl.py", line 388, in run_asgi
    result = await app(self.scope, self.receive, self.send)
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\uvicorn\middleware\proxy_headers.py", line 45, in __call__
    return await self.app(scope, receive, send)
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\fastapi\applications.py", line 190, in __call__
    await super().__call__(scope, receive, send)
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\starlette\applications.py", line 111, in __call__
    await self.middleware_stack(scope, receive, send)
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\starlette\middleware\errors.py", line 181, in __call__
    raise exc from None
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\starlette\middleware\errors.py", line 159, in __call__
    await self.app(scope, receive, _send)
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\starlette\exceptions.py", line 82, in __call__
    raise exc from None
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\starlette\exceptions.py", line 71, in __call__
    await self.app(scope, receive, sender)
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\starlette\routing.py", line 566, in __call__
    await route.handle(scope, receive, send)
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\starlette\routing.py", line 227, in handle
    await self.app(scope, receive, send)
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\starlette\routing.py", line 41, in app
    response = await func(request)
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\fastapi\routing.py", line 196, in app
    response_data = await serialize_response(
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\fastapi\routing.py", line 124, in serialize_response

    return jsonable_encoder(response_content)
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\fastapi\encoders.py", line 102, in jsonable_encoder
    jsonable_encoder(
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\fastapi\encoders.py", line 140, in jsonable_encoder
    return jsonable_encoder(
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\fastapi\encoders.py", line 88, in jsonable_encoder
    encoded_value = jsonable_encoder(
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\fastapi\encoders.py", line 88, in jsonable_encoder
    encoded_value = jsonable_encoder(
  File "d:\users\kendo\documents\git\empathy\kala_api\env\lib\site-packages\fastapi\encoders.py", line 139, in jsonable_encoder
    raise ValueError(errors)
ValueError: [TypeError('cannot convert dictionary update sequence element #0 to a sequence'), TypeError('vars() argument must have __dict__ attribute')]

Answer 1

requests.get()是同步的。没什么可等的了。调用完成后，内容字节是完全可用的。删除await。

for img in body['images']:
    r = requests.get(img['url'])
    dw_image = Image.open(BytesIO(r.content))
    images.append( (img['id'], dw_image) )

如果你有冒险精神(或者想要了解迪克特的理解)，你可以用一行替换整个循环。

@app.post("/v1/img_color")
async def img_color(request: Request):
    body = await request.json()
    return {img['id']: Image.open(BytesIO(requests.get(img['url']).content)) for img in body['images']}