FastAPI Advanced Error Handling

Advanced Error Handling in FastAPI

from fastapi import Request
from fastapi.responses import JSONResponse
from fastapi.exceptions import RequestValidationError

class NotFoundError(Exception):
    def __init__(self, resource: str, id: int):
        self.message = resource + " #" + str(id) + " not found"
        self.code    = 404

class AuthError(Exception):
    def __init__(self, reason: str = "Unauthorized"):
        self.message = reason
        self.code    = 401

@app.exception_handler(NotFoundError)
async def not_found_handler(request: Request, exc: NotFoundError):
    return JSONResponse(status_code=exc.code,
                        content={"detail": exc.message})

@app.exception_handler(AuthError)
async def auth_handler(request: Request, exc: AuthError):
    return JSONResponse(status_code=exc.code,
        content={"detail": exc.message},
        headers={"WWW-Authenticate": "Bearer"})

@app.exception_handler(RequestValidationError)
async def validation_handler(request: Request, exc):
    return JSONResponse(status_code=422,
                        content={"errors": exc.errors()})

# Usage
raise NotFoundError("Post", 42)
raise AuthError("Token expired")