```

## Description from docstring

As descriptions tend to be long and cover multiple lines, you can declare the *path operation* description in the function <abbr title="a multi-line string as the first expression inside a function (not assigned to any variable) used for documentation">docstring</abbr> and **FastAPI** will read it from there.

For these cases, your **FastAPI** application has an attribute `app.dependency_overrides`, it is a simple `dict`.

To override a dependency for testing, you put as a key the original dependency (a function), and as the value, your dependency override (another function).

And then **FastAPI** will call that override instead of the original dependency.

=== "Python 3.10+"

    ```Python hl_lines="26-27  30"

```

そのため、`Depends`と一緒に使うことができます。

### 使い方

これで`oauth2_scheme`を`Depends`で依存関係に渡すことができます。

```Python hl_lines="10"
{!../../../docs_src/security/tutorial001.py!}
```

この依存関係は、*path operation function*のパラメーター`token`に代入される`str`を提供します。

**FastAPI**は、この依存関係を使用してOpenAPIスキーマ (および自動APIドキュメント) で「セキュリティスキーム」を定義できることを知っています。

!!! info "技術詳細"

from fastapi.routing import APIRoute
from pydantic import BaseModel


def custom_generate_unique_id(route: APIRoute):
    return f"{route.tags[0]}-{route.name}"


app = FastAPI(generate_unique_id_function=custom_generate_unique_id)


class Item(BaseModel):
    name: str
    price: float


class ResponseMessage(BaseModel):
    message: str


class User(BaseModel):
    username: str

sequenceDiagram

participant code as Code
participant function as say_hi()
participant execute as Execute function

    rect rgba(0, 255, 0, .1)
        code ->> function: say_hi(name="Camila")
        function ->> execute: 执行函数代码
        execute ->> code: 返回结果
    end

    rect rgba(0, 255, 255, .1)
        code ->> function: say_hi(name="Camila")
        function ->> code: 返回存储的结果
    end

型を使用した標準的なPythonを記述します:

```Python
from datetime import date

from pydantic import BaseModel

# Declare a variable as a str
# and get editor support inside the function
def main(user_id: str):
    return user_id


# A Pydantic model
class User(BaseModel):
    id: int
    name: str
    joined: date
```

これは以下のように用いられます:

```Python

                current_generate_unique_id = get_value_or_default(
                    route.generate_unique_id_function,
                    router.generate_unique_id_function,
                    generate_unique_id_function,
                    self.generate_unique_id_function,
                )
                self.add_api_route(
                    prefix + route.path,
                    route.endpoint,

        </ul>
        <script>
        var ws = null;
            function connect(event) {
                var itemId = document.getElementById("itemId")
                var token = document.getElementById("token")
                ws = new WebSocket("ws://localhost:8000/items/" + itemId.value + "/ws?token=" + token.value);
                ws.onmessage = function(event) {
                    var messages = document.getElementById('messages')

As all these methods are `async` methods, you need to "await" them.

For example, inside of an `async` *path operation function* you can get the contents with:

```Python
contents = await myfile.read()
```

If you are inside of a normal `def` *path operation function*, you can access the `UploadFile.file` directly, for example:

```Python
contents = myfile.file.read()
```

The key factor is that a dependency should be a "callable".

A "**callable**" in Python is anything that Python can "call" like a function.

So, if you have an object `something` (that might _not_ be a function) and you can "call" it (execute it) like:

```Python
something()
```

or

```Python
something(some_argument, some_keyword_argument="foo")
```

then it is a "callable".

## Classes as dependencies