O Python possui suporte para "dicas de tipo" ou "type hints" (também chamado de "anotações de tipo" ou "type annotations")

Esses **"type hints"** são uma sintaxe especial que permite declarar o <abbr title = "por exemplo: str, int, float, bool">tipo</abbr> de uma variável.

Ao declarar tipos para suas variáveis, editores e ferramentas podem oferecer um melhor suporte.

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.

In this case, the database session would be held until the response is finished being sent, but if you don't use it, then it wouldn't be necessary to hold it.

Here's how it could look like:

{* ../../docs_src/dependencies/tutorial013_an_py310.py *}

The exit code, the automatic closing of the `Session` in:

{* ../../docs_src/dependencies/tutorial013_an_py310.py ln[19:21] *}

        Class<?> beanType = bean.getClass();

        // Find the default "set" method
        MethodInfo setterInfo = findCachedMethod(beanType, "", null);
        if (setterInfo == null) {
            // Look for any method named "set" with one parameter
            Map<String, MethodInfo> classMethodCache = METHOD_CACHE.computeIfAbsent(beanType, this::buildMethodCache);
            setterInfo = classMethodCache.get("set");
        }

  else
    MAVEN_OPTS="$_jvm_config"
  fi
fi
if [ -n "$MAVEN_DEBUG_SCRIPT" ]; then
  echo "[DEBUG] Final MAVEN_OPTS: $MAVEN_OPTS" >&2
fi
LAUNCHER_JAR=`echo "$MAVEN_HOME"/boot/plexus-classworlds-*.jar`
LAUNCHER_CLASS=org.codehaus.plexus.classworlds.launcher.Launcher

# For Cygwin and MinGW, switch paths to Windows format before running java(1) command
if $cygwin || $mingw ; then

</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):

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