Python tiene soporte para "anotaciones de tipos" opcionales (también llamadas "type hints").

Estas **"anotaciones de tipos"** o type hints son una sintaxis especial que permite declarar el <abbr title="por ejemplo: str, int, float, bool">tipo</abbr> de una variable.

Al declarar tipos para tus variables, los editores y herramientas te pueden proporcionar un mejor soporte.

    This is a reference for the Maven Toolchains descriptor.
    <p>The default location for the toolchains file is {@code ~/.m2/toolchains.xml}
    <p>A Toolchain is a preconfigured object that Maven plugins can use for tool configuration retrieval (location and other information).
    <p>The <a href="/plugins/maven-toolchains-plugin/">toolchains-plugin</a> can read available toolchains on the user's computer

</p>

<pre>
const c = 3 &lt; 4            // c is the untyped boolean constant true

type MyBool bool
var x, y int
var (
	// The result of a comparison is an untyped boolean.
	// The usual assignment rules apply.
	b3        = x == y // b3 has type bool
	b4 bool   = x == y // b4 has type bool
	b5 MyBool = x == y // b5 has type MyBool
)
</pre>

<p>

from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):

	// STS Router
	stsRouter := router.NewRoute().PathPrefix(SlashSeparator).Subrouter()

	// Assume roles with no JWT, handles AssumeRole.
	stsRouter.Methods(http.MethodPost).MatcherFunc(func(r *http.Request, rm *mux.RouteMatch) bool {
		ctypeOk := wildcard.MatchSimple("application/x-www-form-urlencoded*", r.Header.Get(xhttp.ContentType))
		authOk := wildcard.MatchSimple(signV4Algorithm+"*", r.Header.Get(xhttp.Authorization))

同样，还有很多兼容工具，包括多种语言的代码生成工具。

## Pydantic

FastAPI 充分地利用了 <a href="https://docs.pydantic.dev/" class="external-link" target="_blank">Pydantic</a> 的优势，用它在后台校验数据。众所周知，Pydantic 擅长的就是数据校验。

同样，`str`、`float`、`bool` 以及很多复合数据类型都可以使用类型声明。

下一章介绍详细内容。

## 顺序很重要

有时，*路径操作*中的路径是写死的。

比如要使用 `/users/me` 获取当前用户的数据。

然后还要使用 `/users/{user_id}`，通过用户 ID 获取指定用户的数据。

Você pode usar as mesmas declarações de tipo com `str`, `float`, `bool` e muitos outros tipos de dados complexos.

Vários deles são explorados nos próximos capítulos do tutorial.

## A ordem importa { #order-matters }

	dataBlocks                   int
	onDisks, offDisks            int
	blocksize, data              int64
	offset                       int
	algorithm                    BitrotAlgorithm
	shouldFail, shouldFailQuorum bool
}{
	{dataBlocks: 2, onDisks: 4, offDisks: 0, blocksize: int64(blockSizeV2), data: oneMiByte, offset: 0, algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},                             // 0

///

/// note | 笔记

因为默认值为 `= None`，FastAPI 把 `q` 识别为可选参数。

FastAPI 不使用 `Optional[str]` 中的 `Optional`（只使用 `str`），但 `Optional[str]` 可以帮助编辑器发现代码中的错误。

///

## 查询参数类型转换

参数还可以声明为 `bool` 类型，FastAPI 会自动转换参数类型：


{* ../../docs_src/query_params/tutorial003_py310.py hl[7] *}

本例中，访问：

```
http://127.0.0.1:8000/items/foo?short=1
```

或

```

                "count": count,
                "avatarUrl": author.avatarUrl,
                "url": author.url,
            }
    return users


def update_content(*, content_path: Path, new_content: Any) -> bool:
    old_content = content_path.read_text(encoding="utf-8")

    new_content = yaml.dump(new_content, sort_keys=False, width=200, allow_unicode=True)
    if old_content == new_content: