Exceptions - FastAPI 0.159.1 API reference

Class	Module	Summary
`EndpointContext`	fastapi.exceptions	—
`HTTPException`	fastapi.exceptions	An HTTP exception you can raise in your own code to show errors to the client.
`WebSocketException`	fastapi.exceptions	A WebSocket exception you can raise in your own code to show errors to the client.
`FastAPIError`	fastapi.exceptions	A generic, FastAPI-specific error.
`DependencyScopeError`	fastapi.exceptions	A dependency declared that it depends on another dependency with an invalid
`ValidationException`	fastapi.exceptions	—
`RequestValidationError`	fastapi.exceptions	—
`WebSocketRequestValidationError`	fastapi.exceptions	—
`ResponseValidationError`	fastapi.exceptions	—
`PydanticV1NotSupportedError`	fastapi.exceptions	A pydantic.v1 model is used, which is no longer supported.
`FastAPIDeprecationWarning`	fastapi.exceptions	A custom deprecation warning as DeprecationWarning is ignored

Raising an HTTP error

from fastapi import FastAPI, HTTPException

app = FastAPI()


@app.get("/items/{item_id}")
async def read_item(item_id: int):
    if item_id < 0:
        raise HTTPException(status_code=404, detail="Item not found")
    return {"item_id": item_id}

Custom exception handlers

@app.exception_handler(HTTPException)
async def http_exception_handler(request, exc):
    return JSONResponse({"detail": exc.detail}, status_code=exc.status_code)