│       ├── __init__.py  # makes "internal" a "Python subpackage"
│       └── admin.py     # "admin" submodule, e.g. import app.internal.admin
```

## `APIRouter`

Let's say the file dedicated to handling just users is the submodule at `/app/routers/users.py`.

You want to have the *path operations* related to your users separated from the rest of the code, to keep it organized.

from fastapi.testclient import TestClient

from docs_src.handling_errors.tutorial003 import app

client = TestClient(app)


def test_get():
    response = client.get("/unicorns/shinny")
    assert response.status_code == 200, response.text
    assert response.json() == {"unicorn_name": "shinny"}


def test_get_exception():
    response = client.get("/unicorns/yolo")
    assert response.status_code == 418, response.text

from fastapi.testclient import TestClient

from docs_src.handling_errors.tutorial001 import app

client = TestClient(app)


def test_get_item():
    response = client.get("/items/foo")
    assert response.status_code == 200, response.text
    assert response.json() == {"item": "The Foo Wrestlers"}


def test_get_item_not_found():
    response = client.get("/items/bar")
    assert response.status_code == 404, response.text

!!! tip
    Notice that the query `token` will be handled by a dependency.

With that you can connect the WebSocket and then send and receive messages:

<img src="/img/tutorial/websockets/image05.png">

## Handling disconnections and multiple clients

When a WebSocket connection is closed, the `await websocket.receive_text()` will raise a `WebSocketDisconnect` exception, which you can then catch and handle like in this example.

from dirty_equals import IsDict
from fastapi.testclient import TestClient

from docs_src.handling_errors.tutorial006 import app

client = TestClient(app)


def test_get_validation_error():
    response = client.get("/items/foo")
    assert response.status_code == 422, response.text
    assert response.json() == IsDict(
        {
            "detail": [
                {
                    "type": "int_parsing",

# Security

There are many ways to handle security, authentication and authorization.

And it normally is a complex and "difficult" topic.

In many frameworks and systems just handling security and authentication takes a big amount of effort and code (in many cases it can be 50% or more of all the code written).

    This is for client errors, invalid authentication, invalid data, etc. Not for server
    errors in your code.

    Read more about it in the
    [FastAPI docs for Handling Errors](https://fastapi.tiangolo.com/tutorial/handling-errors/).

    ## Example

    ```python
    from fastapi import FastAPI, HTTPException

    app = FastAPI()

    items = {"foo": "The Foo Wrestlers"}

Таким же образом вы можете поднять исключение `HTTPException` или что-то подобное в завершающем коде, после `yield`.

Код выхода в зависимостях с `yield` выполняется *после* отправки ответа, поэтому [Обработчик исключений](../handling-errors.md#install-custom-exception-handlers){.internal-link target=_blank} уже будет запущен. В коде выхода (после `yield`) нет ничего, перехватывающего исключения, брошенные вашими зависимостями.

    ```

Eine Alternative zum Abfangen von Exceptions (und möglicherweise auch zum Auslösen einer weiteren `HTTPException`) besteht darin, einen [benutzerdefinierten Exceptionhandler](../handling-errors.md#benutzerdefinierte-exceptionhandler-definieren){.internal-link target=_blank} zu erstellen.

## Ausführung von Abhängigkeiten mit `yield`

It is a plug-in for many frameworks (and there's a plug-in for Starlette too).

The way it works is that you write the definition of the schema using YAML format inside the docstring of each function handling a route.

And it generates OpenAPI schemas.

That's how it works in Flask, Starlette, Responder, etc.

But then, we have again the problem of having a micro-syntax, inside of a Python string (a big YAML).