```

</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

```

</div>

////

## Read env vars in Python

You could also create environment variables **outside** of Python, in the terminal (or with any other method), and then **read them in Python**.

For example you could have a file `main.py` with:

```Python hl_lines="3"
import os

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

/// tip

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!}
```

### Nur modernes Python

Alles basiert auf **Python 3.8 Typ**-Deklarationen (dank Pydantic). Es muss keine neue Syntax gelernt werden, nur standardisiertes modernes Python.

Wenn Sie eine zweiminütige Auffrischung benötigen, wie man Python-Typen verwendet (auch wenn Sie FastAPI nicht benutzen), schauen Sie sich das kurze Tutorial an: [Einführung in Python-Typen](python-types.md){.internal-link target=_blank}.

//// 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"