That's why, as said in the official website:

> Requests is one of the most downloaded Python packages of all time

The way you use it is very simple. For example, to do a `GET` request, you would write:

```Python
response = requests.get("http://example.com/some/url")
```

The FastAPI counterpart API *path operation* could look like:

```Python hl_lines="1"
@app.get("/some/url")
def read_url():

Provided directly by Starlette, but you can import it from `fastapi`:

```python
from fastapi.websockets import WebSocketDisconnect, WebSocketState
```

::: fastapi.websockets.WebSocketDisconnect

When a client disconnects, a `WebSocketDisconnect` exception is raised, you can catch it.

You can import it directly form `fastapi`:

```python
from fastapi import WebSocketDisconnect
```

它们处在某种意义上的“对立端”，彼此互补。

Requests 设计非常简单直观，易于使用，且有合理的默认值。同时它也非常强大、可定制。

这就是为什么，正如其官网所说：

> Requests 是有史以来下载量最高的 Python 包之一

它的用法非常简单。例如，进行一次 `GET` 请求，你会这样写：

```Python
response = requests.get("http://example.com/some/url")
```

对应地，FastAPI 的 API 路径操作可能看起来是这样的：

```Python hl_lines="1"
@app.get("/some/url")
def read_url():
    return {"message": "Hello World"}
```

But a variable like `user-agent` is invalid in Python.

So, by default, `Header` will convert the parameter names characters from underscore (`_`) to hyphen (`-`) to extract and document the headers.

Also, HTTP headers are case-insensitive, so, you can declare them with standard Python style (also known as "snake_case").

# 路径参数 { #path-parameters }

你可以使用与 Python 字符串格式化相同的语法声明路径“参数”或“变量”：

{* ../../docs_src/path_params/tutorial001_py310.py hl[6:7] *}

路径参数 `item_id` 的值会作为参数 `item_id` 传递给你的函数。

运行示例并访问 [http://127.0.0.1:8000/items/foo](http://127.0.0.1:8000/items/foo)，可获得如下响应：

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

## 声明路径参数的类型 { #path-parameters-with-types }

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：

Pydantic 使用：

* [`email-validator`](https://github.com/JoshData/python-email-validator) - 用于 email 校验。

Starlette 使用：

* [`httpx`](https://www.python-httpx.org) - 使用 `TestClient` 时需要。
* [`jinja2`](https://jinja.palletsprojects.com) - 使用默认模板配置时需要。
* [`python-multipart`](https://github.com/Kludex/python-multipart) - 使用 `request.form()` 支持表单<dfn title="将 HTTP 请求中的字符串转换为 Python 数据">「解析」</dfn>时需要。

FastAPI 使用：

Remember I told you before that `Annotated` can be used to add metadata to your parameters in the [Python Types Intro](../python-types.md#type-hints-with-metadata-annotations)?

Now it's the time to use it with FastAPI. 🚀

We had this type annotation:

```Python
q: str | None = None
```

What we will do is wrap that with `Annotated`, so it becomes:

```Python
q: Annotated[str | None] = None
```

///

## 在 `q` 参数的类型中使用 `Annotated` { #use-annotated-in-the-type-for-the-q-parameter }

还记得我之前在[Python 类型简介](../python-types.md#type-hints-with-metadata-annotations)中说过可以用 `Annotated` 给参数添加元数据吗？

现在正是与 FastAPI 搭配使用它的时候。🚀

我们之前的类型标注是：

```Python
q: str | None = None
```

我们要做的是用 `Annotated` 把它包起来，变成：

```Python
q: Annotated[str | None] = None
```

这两种写法含义相同，`q` 是一个可以是 `str` 或 `None` 的参数，默认是 `None`。

# Code blocks { #code-blocks }

Some text

```python
# This is a sample Python code block
def hello_world():
    # Comment with indentation
    print("Hello, world!")  # Print greeting
```

Some more text

The following block has wrong language code (should be TOML):

```yaml
# This is a sample TOML code block
title = "TOML Example"  # Title of the document
```

And more text

```console

Lo haces con tipos estándar modernos de Python.

No tienes que aprender una nueva sintaxis, los métodos o clases de un paquete específico, etc.

Solo **Python** estándar.

Por ejemplo, para un `int`:

```Python
item_id: int
```

o para un modelo `Item` más complejo:

```Python
item: Item
```

...y con esa única declaración obtienes: