//// tab | Python 3.10+

```Python hl_lines="9-12  16"
{!> ../../docs_src/cookie_param_models/tutorial001_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="9-12  16"
{!> ../../docs_src/cookie_param_models/tutorial001_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="10-13  17"

//// tab | Python 3.10+

```Python hl_lines="9  17"
{!> ../../docs_src/request_files/tutorial001_02_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="9  17"
{!> ../../docs_src/request_files/tutorial001_02_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="10  18"

//// tab | Python 3.9+

```Python hl_lines="9"
{!> ../../docs_src/request_files/tutorial001_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="8"
{!> ../../docs_src/request_files/tutorial001_an.py!}
```

////

//// tab | Python 3.8+ non-Annotated

/// tip | Dica

Utilize a versão com `Annotated` se possível.

///

```Python hl_lines="7"

```Python
from myapp import app
```

#### Больше деталей

Давайте назовём ваш файл `myapp.py`.

Если вы запустите его с помощью:

<div class="termy">

```console
$ python myapp.py
```

</div>

то встроенная переменная `__name__`, автоматически создаваемая Python в вашем файле, будет иметь значение строкового типа `"__main__"`.

Тогда выполнится условие и эта часть кода:

```Python

## 可选参数

同理，把默认值设为 `None` 即可声明**可选的**查询参数：

//// tab | Python 3.10+

```Python hl_lines="7"
{!> ../../docs_src/query_params/tutorial002_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="9"
{!> ../../docs_src/query_params/tutorial002.py!}
```

////

本例中，查询参数 `q` 是可选的，默认值为 `None`。

/// check | "检查"

注意，**FastAPI** 可以识别出 `item_id` 是路径参数，`q` 不是路径参数，而是查询参数。

///

```
.
├── app                  # "app" is a Python package
│   ├── __init__.py      # this file makes "app" a "Python package"
│   ├── main.py          # "main" module, e.g. import app.main
│   ├── dependencies.py  # "dependencies" module, e.g. import app.dependencies
│   └── routers          # "routers" is a "Python subpackage"
│   │   ├── __init__.py  # makes "routers" a "Python subpackage"

* `datetime.datetime`:
    * O `datetime.datetime` do Python.
    * Em requisições e respostas será representado como uma `str` no formato ISO 8601, exemplo: `2008-09-15T15:53:00+05:00`.
* `datetime.date`:
    * O `datetime.date` do Python.
    * Em requisições e respostas será representado como uma `str` no formato ISO 8601, exemplo: `2008-09-15`.
* `datetime.time`:
    * O `datetime.time` do Python.

我们也可以像这样导入它们：

```Python
from app.routers import items, users
```

/// info

第一个版本是「相对导入」：

```Python
from .routers import items, users
```

第二个版本是「绝对导入」：

```Python
from app.routers import items, users
```

要了解有关 Python 包和模块的更多信息，请查阅<a href="https://docs.python.org/3/tutorial/modules.html" class="external-link" target="_blank">关于 Modules 的 Python 官方文档</a>。

///

### 避免名称冲突

有个 `POST` 操作会返回一些错误。

所有*路径操作* 都需要一个`X-Token` 头。

//// tab | Python 3.10+

```Python
{!> ../../docs_src/app_testing/app_b_an_py310/main.py!}
```

////

//// tab | Python 3.9+

```Python
{!> ../../docs_src/app_testing/app_b_an_py39/main.py!}
```

////

//// tab | Python 3.8+

```Python
{!> ../../docs_src/app_testing/app_b_an/main.py!}
```

////

//// tab | Python 3.10+

```Python hl_lines="62-65"
{!> ../../docs_src/security/tutorial005_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="62-65"
{!> ../../docs_src/security/tutorial005_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="63-66"
{!> ../../docs_src/security/tutorial005_an.py!}