# Yol Parametreleri

Yol "parametrelerini" veya "değişkenlerini" Python <abbr title="String Biçimleme: Format String">string biçimlemede</abbr> kullanılan sözdizimi ile tanımlayabilirsiniz.

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

Yol parametresi olan `item_id`'nin değeri, fonksiyonunuza `item_id` argümanı olarak aktarılacaktır.

//// tab | 🐍 3️⃣.6️⃣ & 🔛

```Python hl_lines="30-35"
{!> ../../docs_src/body_updates/tutorial001.py!}
```

////

//// tab | 🐍 3️⃣.9️⃣ & 🔛

```Python hl_lines="30-35"
{!> ../../docs_src/body_updates/tutorial001_py39.py!}
```

////

//// tab | 🐍 3️⃣.1️⃣0️⃣ & 🔛

```Python hl_lines="28-33"
{!> ../../docs_src/body_updates/tutorial001_py310.py!}
```

//// tab | Python 3.10+

```Python hl_lines="1  15"
{!> ../../docs_src/path_operation_configuration/tutorial001_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="3  17"
{!> ../../docs_src/path_operation_configuration/tutorial001_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="3  17"

//// tab | Python 3.10+

```Python hl_lines="1  15"
{!> ../../docs_src/path_operation_configuration/tutorial001_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="3  17"
{!> ../../docs_src/path_operation_configuration/tutorial001_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="3  17"

//// tab | Python 3.9+

```Python hl_lines="6  14  22"
{!> ../../docs_src/dependencies/tutorial008_an_py39.py!}
```

////

//// tab | Python 3.6+

```Python hl_lines="5  13  21"
{!> ../../docs_src/dependencies/tutorial008_an.py!}
```

////

//// tab | Python 3.6+ без Annotated

/// tip | "Подсказка"

//// tab | Python 3.10+

```Python hl_lines="1  15"
{!> ../../docs_src/path_operation_configuration/tutorial001_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="3  17"
{!> ../../docs_src/path_operation_configuration/tutorial001_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="3  17"

# 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`.

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="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"

```

</div>

////

## Omgevingsvariabelen uitlezen in Python

Je kunt omgevingsvariabelen **buiten** Python aanmaken, in de terminal (of met een andere methode) en ze vervolgens **in Python uitlezen**.

Je kunt bijvoorbeeld een bestand `main.py` hebben met:

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip