python-3.x FastAPI - Pydantic -值错误引发内部服务器错误

gtlvzcf8 于 2023-05-19 发布在 Python

关注(0)|答案(3)|浏览(237)

我使用FastAPI和Pydantic。
我的问题-我需要使用Pydantic引发ValueError

from fastapi import FastAPI
from pydantic import BaseModel, validator
from fastapi import Depends, HTTPException

app = FastAPI()

class RankInput(BaseModel):

    rank: int

    @validator('rank')
    def check_if_value_in_range(cls, v):
        """
        check if input rank is within range
        """
        if not 0 < v < 1000001:

            raise ValueError("Rank Value Must be within range (0,1000000)")
            #raise HTTPException(status_code=400, detail="Rank Value Error") - this works But I am looking for a solution using ValueError
        return v

def get_info_by_rank(rank):
    return rank

@app.get('/rank/{rank}')
async def get_rank(value: RankInput = Depends()):
    result = get_info_by_rank(value.rank)
    return result

这段代码在引发ValueError时给出Internal Server Error

INFO:     127.0.0.1:59427 - "GET /info/?rank=-1 HTTP/1.1" 500 Internal Server Error
ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/uvicorn/protocols/http/h11_impl.py", line 396, in run_asgi
    result = await app(self.scope, self.receive, self.send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/uvicorn/middleware/proxy_headers.py", line 45, in __call__
    return await self.app(scope, receive, send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/fastapi/applications.py", line 199, in __call__
    await super().__call__(scope, receive, send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/applications.py", line 111, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/middleware/errors.py", line 181, in __call__
    raise exc from None
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/middleware/errors.py", line 159, in __call__
    await self.app(scope, receive, _send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/exceptions.py", line 82, in __call__
    raise exc from None
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/exceptions.py", line 71, in __call__
    await self.app(scope, receive, sender)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/routing.py", line 566, in __call__
    await route.handle(scope, receive, send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/routing.py", line 227, in handle
    await self.app(scope, receive, send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/routing.py", line 41, in app
    response = await func(request)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/fastapi/routing.py", line 195, in app
    dependency_overrides_provider=dependency_overrides_provider,
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/fastapi/dependencies/utils.py", line 550, in solve_dependencies
    solved = await run_in_threadpool(call, **sub_values)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/concurrency.py", line 34, in run_in_threadpool
    return await loop.run_in_executor(None, func, *args)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "pydantic/main.py", line 400, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 1 validation error for GetInput
rank
  ValueError() takes no keyword arguments (type=type_error)
ERROR:uvicorn.error:Exception in ASGI application
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/uvicorn/protocols/http/h11_impl.py", line 396, in run_asgi
    result = await app(self.scope, self.receive, self.send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/uvicorn/middleware/proxy_headers.py", line 45, in __call__
    return await self.app(scope, receive, send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/fastapi/applications.py", line 199, in __call__
    await super().__call__(scope, receive, send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/applications.py", line 111, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/middleware/errors.py", line 181, in __call__
    raise exc from None
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/middleware/errors.py", line 159, in __call__
    await self.app(scope, receive, _send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/exceptions.py", line 82, in __call__
    raise exc from None
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/exceptions.py", line 71, in __call__
    await self.app(scope, receive, sender)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/routing.py", line 566, in __call__
    await route.handle(scope, receive, send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/routing.py", line 227, in handle
    await self.app(scope, receive, send)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/routing.py", line 41, in app
    response = await func(request)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/fastapi/routing.py", line 195, in app
    dependency_overrides_provider=dependency_overrides_provider,
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/fastapi/dependencies/utils.py", line 550, in solve_dependencies
    solved = await run_in_threadpool(call, **sub_values)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/starlette/concurrency.py", line 34, in run_in_threadpool
    return await loop.run_in_executor(None, func, *args)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "pydantic/main.py", line 400, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 1 validation error for GetInput
rank
  ValueError() takes no keyword arguments (type=type_error)

我也查了https://github.com/tiangolo/fastapi/issues/2180。
但我没能想出解决办法。
我需要做的是用自定义状态码提升ValueError。
注意-我知道我可以通过提高HTTPException来完成任务。
但我正在寻找使用ValueError的解决方案
你能告诉我我哪里做错了吗？
此问题也发布在Github -https://github.com/tiangolo/fastapi/issues/3761

python-3.x

来源：https://stackoverflow.com/questions/68914523/fastapi-pydantic-value-error-raises-internal-server-error

3条答案

按热度按时间

ie3xauqp1#

如果你没有抛出一个HTTPException，那么任何其他未捕获的异常通常都会生成一个500响应（一个Internal Server Error）。如果你的意图是在引发特定异常时使用其他自定义错误消息和HTTP状态进行响应-比如ValueError-那么你可以使用添加全局异常处理程序到你的应用中：

from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse

@app.exception_handler(ValueError)
async def value_error_exception_handler(request: Request, exc: ValueError):
    return JSONResponse(
        status_code=400,
        content={"message": str(exc)},
    )

这将给予一个400响应（或者您可以将状态代码更改为您喜欢的任何代码），如下所示：

{
    "message": "Value Must be within range (0,1000000)"
}

赞(0）回复(0）举报 2023-05-19

hsvhsicv2#

请注意，pydantic期望验证器产生ValueError、TypeError或AssertionError（参见docs），pydantic将其转换为ValidationError。
此外，根据FastAPI的文档：
当请求包含无效数据时，FastAPI会在内部引发RequestValidationError。
和
RequestValidationError是Pydantic的ValidationError的子类。
这样做的结果是，在pydantic的Model验证期间引发的标准Validation错误将被转换为422 Unprocessable Entity，并且响应主体将包含验证失败的详细原因。
(As旁注：pydantic带有约束类型，允许约束基本数据类型，而无需编写显式验证器。
如果上面的内容不令人满意，并且您希望更改行为，下面是我的方法（有关ValidationError处理的详细信息，请参阅此处）：

from fastapi import Depends, FastAPI, Request, status
from fastapi.exceptions import RequestValidationError
from fastapi.exception_handlers import request_validation_exception_handler
from fastapi.responses import JSONResponse
from pydantic import BaseModel, conint

class RankInput(BaseModel):
    # Constrained integer, must be greater than or equal to 0
    # and less than or equal to 1 million.
    rank: conint(ge=0, le=1_000_000)

async def rank_out_of_bound_handler(request: Request, exc: RequestValidationError):

    validation_errors = exc.errors()
    for err in validation_errors:
        # You could check for other things here as well, e.g. the error type.
        if "rank" in err["loc"]:
            return JSONResponse(
                status_code=status.HTTP_400_BAD_REQUEST,
                content={"message": "Rank must be in range [0, 1000000]."}
            )

    # Default response in every other case.
    return await request_validation_exception_handler(request, exc)

def get_info_by_rank(rank):
    return rank

app = FastAPI(
    exception_handlers={RequestValidationError: rank_out_of_bound_handler},
)

@app.get('/rank/{rank}')
async def get_rank(value: RankInput = Depends()):
    result = get_info_by_rank(value.rank)
    return result

对端点的调用现在给出：

$ curl -i "http://127.0.0.1:8000/rank/1"
HTTP/1.1 200 OK
date: Sat, 28 Aug 2021 20:47:58 GMT
server: uvicorn
content-length: 1
content-type: application/json

1

$  curl -i "http://127.0.0.1:8000/rank/-1"
HTTP/1.1 400 Bad Request
date: Sat, 28 Aug 2021 20:48:24 GMT
server: uvicorn
content-length: 49
content-type: application/json

{"message":"Rank must be in range [0, 1000000]."}

$ curl -i "http://127.0.0.1:8000/rank/1000001"
HTTP/1.1 400 Bad Request
date: Sat, 28 Aug 2021 20:48:51 GMT
server: uvicorn
content-length: 49
content-type: application/json

{"message":"Rank must be in range [0, 1000000]."}

如果你要添加一个使用相同模型的不同端点，异常处理程序也会自动处理这个问题，例如：

@app.get('/other-rank/{rank}')
async def get_other_rank(value: RankInput = Depends()):
    result = get_info_by_rank(value.rank)
    return result

$ curl -i "http://127.0.0.1:8000/other-rank/-1"
HTTP/1.1 400 Bad Request
date: Sat, 28 Aug 2021 20:54:16 GMT
server: uvicorn
content-length: 49
content-type: application/json

{"message":"Rank must be in range [0, 1000000]."}

如果这不是你要找的，你能解释一下你为什么要提出一个ValueError吗？

赞(0）回复(0）举报 2023-05-19

wrrgggsh3#

您遇到了FastAPI bug/讨论：https://github.com/tiangolo/fastapi/issues/1474
你可能会期望，如果Pydantic模型在Depends()中引发ValidationError，那么FastAPI会将其转换为RequestValidationError，就像它在请求主体的模型中遇到一个一样。但事实并非如此这就是窃听器的作用。
上面链接的bug中有一些解决方案。
我更喜欢的一个稍微简单一点的选择是添加一个类方法来捕获ValidationError并将其 Package 到RequestValidationError中，就像Pydantic对请求体所做的那样：

from pydantic.error_wrappers import ErrorWrapper

class RankInput(BaseModel):
    ...
    @classmethod
    def from_path(cls, *, rank):
        """For use in Depends when extracting a model from the path. FastAPI doesn't
        automatically create a RequestValidationError from a ValidationError during
        Depends processing: https://github.com/tiangolo/fastapi/issues/1474
        """
        try:
            return cls(rank=rank)
        except ValidationError as ex:
            raise RequestValidationError([ErrorWrapper(ex, ("path"))])

async def get_rank(value: RankInput = Depends(RankInput.from_path)):
    ...

我肯定不会***做的是为ValueError或ValidationError实现自定义错误处理程序，或者返回自定义JSONResponse而不是引发异常。正如FastAPI文档所说：
如果你在响应中或代码中的任何地方（而不是在客户端的请求中）有一个Pydantic ValidationError，它实际上是代码中的一个bug。
这也可以说适用于ValueError。
返回自定义JSONResponse的问题是，您必须完成所有工作，以确保它遵循与FastAPI从RequestValidationError生成的422响应完全相同的格式。

赞(0）回复(0）举报 2023-05-19

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python-3.x FastAPI - Pydantic -值错误引发内部服务器错误

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