```Python hl_lines="7"
{!../../../docs_src/first_steps/tutorial001.py!}
```

Это обычная Python функция.

**FastAPI** будет вызывать её каждый раз при получении `GET` запроса к URL "`/`".

В данном случае это асинхронная функция.

---

Вы также можете определить ее как обычную функцию вместо `async def`:

```Python hl_lines="7"
{!../../../docs_src/first_steps/tutorial003.py!}
```

# First Steps

The simplest FastAPI file could look like this:

```Python
{!../../../docs_src/first_steps/tutorial001.py!}
```

Copy that to a file `main.py`.

Run the live server:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>

```Python hl_lines="1"
{!../../../docs_src/first_steps/tutorial001.py!}
```

`FastAPI` 🐍 🎓 👈 🚚 🌐 🛠️ 👆 🛠️.

!!! note "📡 ℹ"
    `FastAPI` 🎓 👈 😖 🔗 ⚪️➡️ `Starlette`.

    👆 💪 ⚙️ 🌐 <a href="https://www.starlette.io/" class="external-link" target="_blank">💃</a> 🛠️ ⏮️ `FastAPI` 💁‍♂️.

### 🔁 2️⃣: ✍ `FastAPI` "👐"

```Python hl_lines="3"
{!../../../docs_src/first_steps/tutorial001.py!}
```

```Python hl_lines="1"
{!../../../docs_src/first_steps/tutorial001.py!}
```

`FastAPI`は、APIのすべての機能を提供するPythonクラスです。

!!! note "技術詳細"
    `FastAPI`は`Starlette`を直接継承するクラスです。

    `FastAPI`でも<a href="https://www.starlette.io/" class="external-link" target="_blank">Starlette</a>のすべての機能を利用可能です。

### Step 2: `FastAPI`の「インスタンス」を生成

```Python hl_lines="3"
{!../../../docs_src/first_steps/tutorial001.py!}
```

def get_value_or_default(
    first_item: Union[DefaultPlaceholder, DefaultType],
    *extra_items: Union[DefaultPlaceholder, DefaultType],
) -> Union[DefaultPlaceholder, DefaultType]:
    """
    Pass items or `DefaultPlaceholder`s by descending priority.

    The first one to _not_ be a `DefaultPlaceholder` will be returned.

    Otherwise, the first item (a `DefaultPlaceholder`) will be returned.
    """

```Python
    first_name, last_name
```

на:

```Python
    first_name: str, last_name: str
```

Вот и все.

Это аннотации типов:

```Python hl_lines="1"
{!../../../docs_src/python_types/tutorial002.py!}
```

Это не то же самое, что объявление значений по умолчанию, например:

```Python
    first_name="john", last_name="doe"
```

Это другая вещь.

```Python
    first_name, last_name
```

на:

```Python
    first_name: str, last_name: str
```

Ось і все.

Це "type hints":

```Python hl_lines="1"
{!../../../docs_src/python_types/tutorial002.py!}
```

Це не те саме, що оголошення значень за замовчуванням, як це було б з:

```Python
    first_name="john", last_name="doe"
```

Це зовсім інше.

It is used by many companies including Mozilla, Red Hat and Eventbrite.

It was one of the first examples of **automatic API documentation**, and this was specifically one of the first ideas that inspired "the search for" **FastAPI**.

!!! note
    Django REST Framework was created by Tom Christie. The same creator of Starlette and Uvicorn, on which **FastAPI** is based.

!!! tip
    The next sections are **not necessarily "advanced"**.

    And it's possible that for your use case, the solution is in one of them.

## Read the Tutorial first

The next sections assume you already read the main [Tutorial - User Guide: Security](../../tutorial/security/index.md){.internal-link target=_blank}.

    """
    The HTTP authorization credentials in the result of using `HTTPBearer` or
    `HTTPDigest` in a dependency.

    The HTTP authorization header value is split by the first space.

    The first part is the `scheme`, the second part is the `credentials`.

    For example, in an HTTP Bearer token scheme, the client will send a header
    like:

    ```
    Authorization: Bearer deadbeef12346