一个选项是set the status code对应于您的异常，然后返回一个自定义的响应体。
下面是一个简单的玩具示例，使用这种方法来解决手头的问题：

from fastapi import FastAPI, Response, status

myapp = FastAPI()

@myapp.get("/")
async def app_func(response: Response, myparam: str):

    #end point code here

    valid_params = ['a', 'b', 'c']
    
    if myparam not in valid_params:
        #Customize logic, status code, and returned dict as needed

        response.status_code = status.HTTP_400_BAD_REQUEST

        return {'message': 'Oh no! I failed (without detail key)'}

    
    response.status_code = status.HTTP_200_OK
    return {'message': 'Yay! I succeeded!'}

可用状态代码的完整列表可在here中找到。

建议使用FastAPI提供的状态模块，而不是直接使用数字HTTP状态代码。这种方法提高了代码的可读性并降低了出错的可能性。

from fastapi import FastAPI, Response, status

    myapp = FastAPI()

    @myapp.get("/")
    async def app_func(response: Response, myparam: str):
        valid_params = ['a', 'b', 'c']

        if myparam not in valid_params:
            response.status_code = status.HTTP_400_BAD_REQUEST
            return {
                'message': 'Invalid parameter.',
                'detail': f"The provided parameter '{myparam}' is not valid. Valid parameters are: a, b, c"
            }

        response.status_code = status.HTTP_200_OK
        return {'message': 'Yay! I succeeded!'}