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:

```

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",

```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

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.

기본적으로 단일 값은 쿼리 매개변수로 해석되므로, 명시적으로 `Query`를 추가할 필요가 없고, 아래처럼 할 수 있습니다:

```Python hl_lines="27"
{!../../docs_src/body_multiple_params/tutorial004.py!}
```

이렇게:

```Python
q: Optional[str] = None
```

/// info | "정보"

`Body` 또한 `Query`, `Path` 그리고 이후에 볼 다른 것들처럼 동일한 추가 검증과 메타데이터 매개변수를 갖고 있습니다.

///

## 단일 본문 매개변수 삽입하기

Pydantic 모델 `Item`의 `item`을 본문 매개변수로 오직 한개만 갖고있다고 하겠습니다.

O `secrets.compare_digest()` necessita receber `bytes` ou `str` que possuem apenas caracteres ASCII (os em inglês). Isso significa que não funcionaria com caracteres como o `á`, como em `Sebastián`.

    public String generateDocId(final Map<String, Object> map) {
        return UUID.randomUUID().toString().replace("-", StringUtil.EMPTY);
    }

    public String abbreviateLongText(final String str) {
        return StringUtils.abbreviate(str, ComponentUtil.getFessConfig().getMaxLogOutputLengthAsInteger());
    }

    public String normalizeHtmlLang(final String value) {

   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
   *         .collect(
   *             toMultimap(
   *                  str -> str.charAt(0),
   *                  str -> str.substring(1),
   *                  MultimapBuilder.treeKeys().arrayListValues()::build));
   *
   * // is equivalent to
   *
   * static final ListMultimap<Character, String> FIRST_LETTER_MULTIMAP;