# Exceptions - `HTTPException` and `WebSocketException`

These are the exceptions that you can raise to show errors to the client.

When you raise an exception, as would happen with normal Python, the rest of the execution is aborted. This way you can raise these exceptions from anywhere in the code to abort a request and show the error to the client.

You can use:

* `HTTPException`
* `WebSocketException`

    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(),
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,

):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login_for_access_token(
    form_data: Annotated[OAuth2PasswordRequestForm, Depends()],
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(

    except HTTPException:
        state["except"] = True
        raise
    finally:
        state["finally"] = True


@app.put("/invalid-user/{user_id}")
def put_invalid_user(
    user_id: str, name: str = Body(), db: dict = Depends(get_database)
):
    db[user_id] = name
    raise HTTPException(status_code=400, detail="Invalid user")


@app.put("/user/{user_id}")

    hero = session.get(Hero, hero_id)
    if not hero:
        raise HTTPException(status_code=404, detail="Hero not found")
    return hero


@app.delete("/heroes/{hero_id}")
def delete_hero(hero_id: int, session: Session = Depends(get_session)):
    hero = session.get(Hero, hero_id)
    if not hero:
        raise HTTPException(status_code=404, detail="Hero not found")
    session.delete(hero)
    session.commit()

    "title": "towel",
    "size": "XL"
  }
}
```

#### FastAPIs `HTTPException` vs. Starlettes `HTTPException`

**FastAPI** hat seine eigene `HTTPException`.

Und **FastAPI**s `HTTPException`-Fehlerklasse erbt von Starlettes `HTTPException`-Fehlerklasse.

  }
}

```

### FastAPI `HTTPException` vs Starlette `HTTPException`

**FastAPI** 也提供了自有的 `HTTPException`。

**FastAPI** 的 `HTTPException` 继承自 Starlette 的 `HTTPException` 错误类。

它们之间的唯一区别是，**FastAPI** 的 `HTTPException` 可以在响应中添加响应头。

OAuth 2.0 等安全工具需要在内部调用这些响应头。

因此你可以继续像平常一样在代码中触发 **FastAPI** 的 `HTTPException` 。

但注册异常处理器时，应该注册到来自 Starlette 的 `HTTPException`。

):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login(form_data: Annotated[OAuth2PasswordRequestForm, Depends()]):
    user_dict = fake_users_db.get(form_data.username)
    if not user_dict:
        raise HTTPException(status_code=400, detail="Incorrect username or password")

from fastapi import Depends, FastAPI, HTTPException
from typing_extensions import Annotated

app = FastAPI()


class InternalError(Exception):
    pass


def get_username():
    try:
        yield "Rick"
    except InternalError:
        print("Oops, we didn't raise again, Britney 😱")


@app.get("/items/{item_id}")
def get_item(item_id: str, username: Annotated[str, Depends(get_username)]):
    if item_id == "portal-gun":

**FastAPI** verwendet sie intern, um das zu erreichen.

///

## Abhängigkeiten mit `yield` und `HTTPException`.

Sie haben gesehen, dass Ihre Abhängigkeiten `yield` verwenden können und `try`-Blöcke haben können, die Exceptions abfangen.

Auf die gleiche Weise könnten Sie im Exit-Code nach dem `yield` eine `HTTPException` oder ähnliches auslösen.

/// tip | "Tipp"