Raise instead a return

Question

Can anybody help me to understand why not raise an HTTPException when the status is 200 instead a return ?

working with fastApi

A code as example:

@app.delete("/delete")
def delete(id = Query(...,description="Delete ID to be deleted")):
    if id not in dictionary:
        raise HTTPException(status_code=404,detail="Delete Id doesn't exists.")
    del dictionary[id]

    return {"Success":"Delete deleted!"}

I want to understand why not to use as example:

raise HTTPException(status_code=200,detail="Delete deleted!")

Is this a correct way to use it?

Asked By: Ragnar

||

Source

Answer 1

First of all because of the semantics: an exception is a language construct that means something else than returning the result of a function. It breaks the normal flow of the FastAPI application, and I’m guessing it will/could break most middleware handling (such as CORS headers) because suddenly an exception has occurred instead.

Secondly: Because you probably want to return something else than just information under a detail key. It won’t be able to use the response_model mechanism that’s built-in to FastAPI and allows you to tweak and validate the response model for each type of request declaratively (i.e. by configuring the view decorator).

Answered By: MatsLindh

Answer 2

return is better
A lot of times the result should be equal
raise breaks all next middlewares (pre, mid, post)
Here is redirect login page middleware


class Middleware(APIRoute):
    def get_route_handler(self) -> Callable:
        original_route_handler = super().get_route_handler()

    async def custom_route_handler(req: Request) -> Response:
        try:
            res: Response = await original_route_handler(req) #original request
        except HTTPException as e: #catch login exception
            if e.status_code == status.HTTP_403_FORBIDDEN:
                return RedirectResponse(url = Const.DEFAULT_PAGE) #redirect to home page
            else:
                raise e #other exception process normally 
            
        return res

    return custom_route_handler

Answered By: NoUserNoName

Raise instead a return

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