而且添加类型提示一般不会改变原来的运行结果。

现在假设我们又一次正在创建这个函数，这次添加了类型提示。

在同样的地方，通过 `Ctrl+Space` 触发自动补全，你会发现：

<img src="https://fastapi.tiangolo.com/img/python-types/image02.png">

这样，你可以滚动查看选项，直到你找到看起来眼熟的那个：

<img src="https://fastapi.tiangolo.com/img/python-types/image03.png">

## 更多动机

下面是一个已经有类型提示的函数：

```Python hl_lines="1"
{!../../docs_src/python_types/tutorial003.py!}
```

				"chemical/x-xyz",
				"image/x-ms-bmp",
				"image/cgm",
				"image/example",
				"image/fits",
				"image/g3fax",
				"image/gif",
				"image/ief",
				"image/jp2",
				"image/jpeg",
				"image/jpm",
				"image/jpx",
				"image/naplps",
				"image/nitf",
				"image/png",
				"image/prs.btif",
				"image/prs.pti",
				"image/svg+xml",
				"image/t38",

def test_path_operation_img():
    shutil.copy("./docs/en/docs/img/favicon.png", "./image.png")
    response = client.get("/items/foo?img=1")
    assert response.status_code == 200, response.text
    assert response.headers["Content-Type"] == "image/png"
    assert len(response.content)
    os.remove("./image.png")


def test_openapi_schema():
    response = client.get("/openapi.json")

def test_path_operation_img():
    shutil.copy("./docs/en/docs/img/favicon.png", "./image.png")
    response = client.get("/items/foo?img=1")
    assert response.status_code == 200, response.text
    assert response.headers["Content-Type"] == "image/png"
    assert len(response.content)
    os.remove("./image.png")


def test_openapi_schema():
    response = client.get("/openapi.json")

		// Expired policy document

			</arg>
		</postConstruct>
		<postConstruct name="addCondition">
			<arg>"mimetype"</arg>
			<arg>"image/png"
			</arg>
		</postConstruct>
		<postConstruct name="addCondition">
			<arg>"mimetype"</arg>
			<arg>"image/vnd.adobe.photoshop"
			</arg>
		</postConstruct>
		<postConstruct name="addCondition">
			<arg>"mimetype"</arg>
			<arg>"image/photoshop"
			</arg>
		</postConstruct>

cartão de crédito digitado não é válido",badCVV:"O código de segurança do cartão de crédito não é válido",wrongFileDim:"As dimensões da imagem não são válidas",imageTooTall:"a imagem não pode ser mais alta que ",imageTooWide:"a imagem não pode ser mais larga que ",imageTooSmall:"a imagem é muito pequena",min:"min",max:"max",imageRatioNotAccepted:"A proporção da imagem (largura x altura) não é válida",badBrazilTelephoneAnswer:"O número de telefone digitado é inválido",badBrazilCEPAnswer:"O CEP digitado...

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Image(BaseModel):
    url: str
    name: str


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None
    tags: set[str] = set()
    image: Union[Image, None] = None


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item):

services:
  mysql:
    image: 'mysql/mysql-server:latest'
    ports:
      - "127.0.0.1:9910:3306"
    environment:
      - MYSQL_DATABASE=gorm
      - MYSQL_USER=gorm
      - MYSQL_PASSWORD=gorm
      - MYSQL_RANDOM_ROOT_PASSWORD="yes"
  postgres:
    image: 'postgres:latest'
    ports:
      - "127.0.0.1:9920:5432"
    environment:
      - TZ=Asia/Shanghai
      - POSTGRES_DB=gorm
      - POSTGRES_USER=gorm

pkg image, method (*NYCbCrA) SubImage(Rectangle) Image
pkg image, method (*NYCbCrA) YCbCrAt(int, int) color.YCbCr
pkg image, method (*NYCbCrA) YOffset(int, int) int
pkg image, type NYCbCrA struct
pkg image, type NYCbCrA struct, A []uint8
pkg image, type NYCbCrA struct, AStride int
pkg image, type NYCbCrA struct, embedded YCbCr
pkg image/color, method (NYCbCrA) RGBA() (uint32, uint32, uint32, uint32)