This page shows how to customize your fastapi errors. I found this very useful to setup common templates so that I can return the same 404’s both programatically and by default, so it all looks the same to the end user.
from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse
class UnicornException(Exception):
def __init__(self, name: str):
self.name = name
app = FastAPI()
@app.exception_handler(UnicornException)
async def unicorn_exception_handler(request: Request, exc: UnicornException):
return JSONResponse(
status_code=418,
content={"message": f"Oops! {exc.name} did something. There goes a rainbow..."},
)
@app.get("/unicorns/{name}")
async def read_unicorn(name: str):
if name == "yolo":
raise UnicornException(name=name)
return {"unicorn_name": name}
This post sat in draft for months. I stumbled upon it again and found great success returning good error messages based on user preferences. the default remains json, but if a user requests text/html it will be an html response, and text for application/rtf or text/plain