Then create class attributes with fixed values, which will be the available valid values:

{* ../../docs_src/path_params/tutorial005_py310.py hl[1,6:9] *}

/// tip

If you are wondering, "AlexNet", "ResNet", and "LeNet" are just names of Machine Learning <dfn title="Technically, Deep Learning model architectures">models</dfn>.

///

### Declare a *path parameter* { #declare-a-path-parameter }

繼承自 `str` 之後，API 文件就能知道這些值的型別必須是 `string`，並能正確地呈現。

然後建立具有固定值的類別屬性，這些就是可用的有效值：

{* ../../docs_src/path_params/tutorial005_py310.py hl[1,6:9] *}

/// tip

如果你在想，「AlexNet」、「ResNet」和「LeNet」只是一些機器學習 <dfn title="嚴格來說是深度學習的模型架構">模型</dfn> 的名字。

///

### 宣告一個「路徑參數」 { #declare-a-path-parameter }

接著使用你建立的列舉類別（`ModelName`）作為型別註記，建立一個「路徑參數」：

导入 `Enum` 并创建继承自 `str` 和 `Enum` 的子类。

通过从 `str` 继承，API 文档就能把值的类型定义为**字符串**，并且能正确渲染。

然后，创建包含固定值的类属性，这些固定值是可用的有效值：

{* ../../docs_src/path_params/tutorial005_py310.py hl[1,6:9] *}

/// tip | 提示

**AlexNet**、**ResNet**、**LeNet** 是机器学习<dfn title="技术上来说是深度学习模型架构">模型</dfn>的名字。

///

### 声明路径参数 { #declare-a-path-parameter }

使用 Enum 类（`ModelName`）创建使用类型注解的路径参数：

from enum import Enum

from fastapi import FastAPI


class ModelName(str, Enum):
    alexnet = "alexnet"
    resnet = "resnet"
    lenet = "lenet"


app = FastAPI()


@app.get("/models/{model_name}")
async def get_model(model_name: ModelName):
    if model_name is ModelName.alexnet:
        return {"model_name": model_name, "message": "Deep Learning FTW!"}

    if model_name.value == "lenet":

Luego crea atributos de clase con valores fijos, que serán los valores válidos disponibles:

{* ../../docs_src/path_params/tutorial005_py310.py hl[1,6:9] *}

/// tip | Consejo

Si te estás preguntando, "AlexNet", "ResNet" y "LeNet" son solo nombres de <dfn title="Técnicamente, arquitecturas de modelos de Deep Learning">modelos</dfn> de Machine Learning.

///

### Declarar un *path parameter* { #declare-a-path-parameter }

Sonra, kullanılabilir geçerli değerler olacak sabit değerli class attribute'ları oluşturun:

{* ../../docs_src/path_params/tutorial005_py310.py hl[1,6:9] *}

/// tip | İpucu

Merak ediyorsanız: "AlexNet", "ResNet" ve "LeNet", Makine Öğrenmesi <dfn title="Teknik olarak, Derin Öğrenme model mimarileri">modelleri</dfn>nin sadece isimleridir.

///

### Bir *Path Parameter* Tanımlayalım { #declare-a-path-parameter }

Em seguida, crie atributos de classe com valores fixos, que serão os valores válidos disponíveis:

{* ../../docs_src/path_params/tutorial005_py310.py hl[1,6:9] *}

/// tip | Dica
Se você está se perguntando, "AlexNet", "ResNet" e "LeNet" são apenas nomes de modelos de Aprendizado de Máquina <dfn title="Tecnicamente, arquiteturas de modelos de Deep Learning">modelos</dfn>.
///

### Declare um parâmetro de path { #declare-a-path-parameter }