# Paramètres de chemin

Vous pouvez déclarer des "paramètres" ou "variables" de chemin avec la même syntaxe que celle utilisée par le
<a href="https://docs.python.org/fr/3/library/string.html#format-string-syntax" class="external-link" target="_blank">formatage de chaîne Python</a> :


```Python hl_lines="6-7"
{!../../docs_src/path_params/tutorial001.py!}
```

La valeur du paramètre `item_id` sera transmise à la fonction dans l'argument `item_id`.

//// tab | Python 3.10+

```Python hl_lines="1  3  12-16"
{!> ../../docs_src/extra_data_types/tutorial001_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="1  3  12-16"
{!> ../../docs_src/extra_data_types/tutorial001_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="1  3  13-17"

但此处要把待检验的固定内容定义为参数。

## **可调用**实例

Python 可以把类实例变为**可调用项**。

这里说的不是类本身（类本就是可调用项），而是类实例。

为此，需要声明 `__call__` 方法：

```Python hl_lines="10"
{!../../docs_src/dependencies/tutorial011.py!}
```

本例中，**FastAPI**  使用 `__call__` 检查附加参数及子依赖项，稍后，还要调用它向*路径操作函数*传递值。

## 参数化实例

接下来，使用 `__init__` 声明用于**参数化**依赖项的实例参数：

```Python hl_lines="7"
{!../../docs_src/dependencies/tutorial011.py!}
```

//// tab | Python 3.10+

```Python hl_lines="9-13  17"
{!> ../../docs_src/query_param_models/tutorial001_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="8-12  16"
{!> ../../docs_src/query_param_models/tutorial001_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="10-14  18"

from fastapi import FastAPI, Form
from fastapi.testclient import TestClient

app = FastAPI()


@app.post("/form/python-list")
def post_form_param_list(items: list = Form()):
    return items


@app.post("/form/python-set")
def post_form_param_set(items: set = Form()):
    return items


@app.post("/form/python-tuple")
def post_form_param_tuple(items: tuple = Form()):
    return items


client = TestClient(app)

//// tab | Python 3.10+

```Python hl_lines="4  78"
{!> ../../docs_src/security/tutorial003_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="4  78"
{!> ../../docs_src/security/tutorial003_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="4  79"
{!> ../../docs_src/security/tutorial003_an.py!}
```

//// tab | Python 3.10+

```Python hl_lines="4  78"
{!> ../../docs_src/security/tutorial003_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="4  78"
{!> ../../docs_src/security/tutorial003_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="4  79"
{!> ../../docs_src/security/tutorial003_an.py!}
```

//// tab | Python 3.10+

```Python hl_lines="16  21"
{!> ../../docs_src/response_model/tutorial001_01_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="18  23"
{!> ../../docs_src/response_model/tutorial001_01_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="18  23"
{!> ../../docs_src/response_model/tutorial001_01.py!}

## 例子

下面是一个*路径操作*的示例，其中的参数使用了上面的一些类型。

//// tab | Python 3.10+

```Python hl_lines="1  3  12-16"
{!> ../../docs_src/extra_data_types/tutorial001_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="1  3  12-16"
{!> ../../docs_src/extra_data_types/tutorial001_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="1  3  13-17"

Ele deve ser uma lista de `Depends()`:

//// tab | Python 3.9+

```Python hl_lines="19"
{!> ../../docs_src/dependencies/tutorial006_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="18"
{!> ../../docs_src/dependencies/tutorial006_an.py!}
```

////

//// tab | Python 3.8 non-Annotated

/// tip | "Dica"

Utilize a versão com `Annotated` se possível