### 步骤 1：导入 `FastAPI`

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

`FastAPI` 是一个为你的 API 提供了所有功能的 Python 类。

!!! note "技术细节"
    `FastAPI` 是直接从 `Starlette` 继承的类。

    你可以通过 `FastAPI` 使用所有的 Starlette 的功能。

### 步骤 2：创建一个 `FastAPI`「实例」

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

这里的变量 `app` 会是 `FastAPI` 类的一个「实例」。

# Security - First Steps

Let's imagine that you have your **backend** API in some domain.

And you have a **frontend** in another domain or in a different path of the same domain (or in a mobile application).

And you want to have a way for the frontend to authenticate with the backend, using a **username** and **password**.

We can use **OAuth2** to build that with **FastAPI**.

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

!!! note
    Jeśli nie znasz różnicy, sprawdź [Async: *"In a hurry?"*](../async.md#in-a-hurry){.internal-link target=_blank}.

### Krok 5: zwróć zawartość

```Python hl_lines="8"
{!../../../docs_src/first_steps/tutorial001.py!}
```

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

!!! note
    Nếu bạn không biết sự khác nhau, kiểm tra [Async: *"Trong khi vội vàng?"*](../async.md#in-a-hurry){.internal-link target=_blank}.

### Bước 5: Nội dung trả về

```Python hl_lines="8"
{!../../../docs_src/first_steps/tutorial001.py!}
```

Nils Lindemann <******@****.***> 1713469999 +0200

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

!!! note "Not"
    Eğer farkı bilmiyorsanız, [Async: *"Aceleniz mi var?"*](../async.md#in-a-hurry){.internal-link target=_blank} sayfasını kontrol edebilirsiniz.

### Adım 5: İçeriği Geri Döndürün

```Python hl_lines="8"
{!../../../docs_src/first_steps/tutorial001.py!}
```

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

!!! note "Nota"
    Si no sabes la diferencia, revisa el [Async: *"¿Tienes prisa?"*](../async.md#tienes-prisa){.internal-link target=_blank}.

### Paso 5: devuelve el contenido

```Python hl_lines="8"
{!../../../docs_src/first_steps/tutorial001.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
$ uvicorn main:app --reload

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
<span style="color: green;">INFO</span>:     Started reloader process [28720]

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

!!! note
    Si vous ne connaissez pas la différence, allez voir la section [Concurrence : *"Vous êtes pressés ?"*](../async.md#vous-etes-presses){.internal-link target=_blank}.

### Étape 5 : retourner le contenu

```Python hl_lines="8"
{!../../../docs_src/first_steps/tutorial001.py!}
```

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

Bu bir Python fonksiyonudur.

Bir `GET` işlemi kullanarak "`/`" URL'sine bir istek geldiğinde **FastAPI** tarafından çağrılır.

Bu durumda bir `async` fonksiyonudur.

---

Bunu `async def` yerine normal bir fonksiyon olarakta tanımlayabilirsiniz.

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