Aynı şekilde, varsayılan değerlerini `None` olarak atayarak isteğe bağlı parametreler tanımlayabilirsiniz:

//// 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!}
```

////

以下の様に実行する場合:

<div class="termy">

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

</div>

Pythonによって自動的に作成されたファイル内の内部変数 `__name__` は、値として文字列 `"__main__"` を持ちます。

なので、以下:

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

は実行されます。

---

そのモジュール (ファイル) をインポートした場合は、こうはなりません。

したがって、次のようなもう一つのファイル `importer.py` がある場合:

```Python
from myapp import app

# Some more code
```

Para receber arquivos enviados, primeiro instale o <a href="https://github.com/Kludex/python-multipart" class="external-link" target="_blank">`python-multipart`</a>.

Garanta que você criou um [ambiente virtual](../virtual-environments.md){.internal-link target=_blank}, o ativou e então o instalou, por exemplo:

```console
$ pip install python-multipart
```

```Python
{!> ../../docs_src/sql_databases/sql_app_py310/schemas.py!}
```

////

* `sql_app/crud.py`:

```Python
{!../../docs_src/sql_databases/sql_app/crud.py!}
```

* `sql_app/main.py`:

//// tab | 🐍 3️⃣.6️⃣ & 🔛

```Python
{!> ../../docs_src/sql_databases/sql_app/main.py!}
```

////

//// tab | 🐍 3️⃣.9️⃣ & 🔛

```Python

# buildifier: disable=load-on-top

workspace(name = "org_tensorflow")

# buildifier: disable=load-on-top

# We must initialize hermetic python first.
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "rules_java",
    sha256 = "c73336802d0b4882e40770666ad055212df4ea62cfa6edf9cb0f9d29828a0934",
    url = "https://github.com/bazelbuild/rules_java/releases/download/5.3.5/rules_java-5.3.5.tar.gz",
)

# 路径参数

FastAPI 支持使用 Python 字符串格式化语法声明**路径参数**（**变量**）：

```Python hl_lines="6-7"
{!../../docs_src/path_params/tutorial001.py!}
```

这段代码把路径参数 `item_id` 的值传递给路径函数的参数 `item_id`。

运行示例并访问 <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>，可获得如下响应：

```JSON
{"item_id":"foo"}
```

## 声明路径参数的类型

使用 Python 标准类型注解，声明路径操作函数中路径参数的类型。

```Python hl_lines="7"

## Generate a TypeScript Frontend Client

Let's start with a simple FastAPI application:

//// tab | Python 3.9+

```Python hl_lines="7-9  12-13  16-17  21"
{!> ../../docs_src/generate_clients/tutorial001_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="9-11  14-15  18  19  23"
{!> ../../docs_src/generate_clients/tutorial001.py!}
```

////

You can set them as follows:

```Python hl_lines="3-16  19-32"
{!../../docs_src/metadata/tutorial001.py!}
```

/// tip

You can write Markdown in the `description` field and it will be rendered in the output.

///

接收上传文件或表单数据，要预先安装 <a href="https://github.com/Kludex/python-multipart" class="external-link" target="_blank">`python-multipart`</a>。

例如，`pip install python-multipart`。

///

## 导入 `File` 与 `Form`

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

## 定义 `File` 与 `Form` 参数

创建文件和表单参数的方式与 `Body` 和 `Query` 一样：

```Python hl_lines="8"

Assim, crie atributos de classe com valores fixos, que serão os valores válidos disponíveis.

```Python hl_lines="1  6-9"
{!../../docs_src/path_params/tutorial005.py!}
```

/// info | "informação"

<a href="https://docs.python.org/3/library/enum.html" class="external-link" target="_blank">Enumerations (ou enums) estão disponíveis no Python</a> desde a versão 3.4.

///

/// tip | "Dica"



///