That means that **any value** read in Python from an environment variable **will be a `str`**, and any conversion to a different type or any validation has to be done in code.

In diesem Fall ist es der `str`:

```Python
"{$callback_url}/invoices/{$request.body.id}"
```

Wenn Ihr API-Benutzer (der externe Entwickler) also einen Request an *Ihre API* sendet, via:

```

def test_path_str_foobar():
    response = client.get("/path/str/foobar")
    assert response.status_code == 200
    assert response.json() == "foobar"


def test_path_str_42():
    response = client.get("/path/str/42")
    assert response.status_code == 200
    assert response.json() == "42"


def test_path_str_True():
    response = client.get("/path/str/True")
    assert response.status_code == 200

func check(t *testing.T, testname string, buf *Buffer, s string) {
	bytes := buf.Bytes()
	str := buf.String()
	if buf.Len() != len(bytes) {
		t.Errorf("%s: buf.Len() == %d, len(buf.Bytes()) == %d", testname, buf.Len(), len(bytes))
	}

	if buf.Len() != len(str) {
		t.Errorf("%s: buf.Len() == %d, len(buf.String()) == %d", testname, buf.Len(), len(str))
	}

	if buf.Len() != len(s) {

func fromSchemaAndJSONMap(schema resource.Schema, data any) (config.Spec, error) {
	// Marshal to json bytes
	str, err := json.Marshal(data)
	if err != nil {
		return nil, err
	}
	out, err := schema.NewInstance()
	if err != nil {
		return nil, err
	}
	if err = config.ApplyJSONStrict(out, string(str)); err != nil {
		return nil, err
	}
	return out, nil

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: Annotated[CommonHeaders, Header()]):
    return headers
```

                            "name": "item_id",
                            "in": "path",
                        }
                    ],
                }
            },
            "/path/str/{item_id}": {
                "get": {
                    "responses": {
                        "200": {
                            "description": "Successful Response",

For this, use the Python standard module <a href="https://docs.python.org/3/library/secrets.html" class="external-link" target="_blank">`secrets`</a> to check the username and password.

`secrets.compare_digest()` needs to take `bytes` or a `str` that only contains ASCII characters (the ones in English), this means it wouldn't work with characters like `á`, as in `Sebastián`.

To handle that, we first convert the `username` and `password` to `bytes` encoding them with UTF-8.

{!../../docs_src/dependencies/tutorial001.py!}
```

大功告成。

只用了**2 行**代码。

依赖项函数的形式和结构与*路径操作函数*一样。

因此，可以把依赖项当作没有「装饰器」（即，没有 `@app.get("/some-path")` ）的路径操作函数。

依赖项可以返回各种内容。

本例中的依赖项预期接收如下参数：

* 类型为 `str` 的可选查询参数 `q`
* 类型为 `int` 的可选查询参数 `skip`，默认值是 `0`
* 类型为 `int` 的可选查询参数 `limit`，默认值是 `100`

然后，依赖项函数返回包含这些值的 `dict`。

### 导入 `Depends`

```Python hl_lines="3"
{!../../docs_src/dependencies/tutorial001.py!}
```

```JSON
{
  "detail": "Item not found"
}
```

/// tip | "Подсказка"

При вызове `HTTPException` в качестве параметра `detail` можно передавать любое значение, которое может быть преобразовано в JSON, а не только `str`.

Вы можете передать `dict`, `list` и т.д.

Они автоматически обрабатываются **FastAPI** и преобразуются в JSON.

///

## Добавление пользовательских заголовков