例えば、NoSQLデータベースに多くのオプション属性を持つモデルがあるが、デフォルト値でいっぱいの非常に長いJSONレスポンスを送信したくない場合です。

### `response_model_exclude_unset`パラメータの使用

*path operation デコレータ*に`response_model_exclude_unset=True`パラメータを設定することができます:

{* ../../docs_src/response_model/tutorial004.py hl[24] *}

そして、これらのデフォルト値はレスポンスに含まれず、実際に設定された値のみが含まれます。

そのため、*path operation*にID`foo`が設定されたitemのリクエストを送ると、レスポンスは以下のようになります（デフォルト値を含まない）:

```JSON
{
    "name": "Foo",

# Count should match the initial count of 10
if [ "${OBJ_COUNT_AFTER_STOP}" -ne 10 ]; then
	echo "Expected 10 objects; received ${OBJ_COUNT_AFTER_STOP}"
	exit 1
fi

./mc ready "${ALIAS_NAME}" --json

OUT=$(./mc cp --quiet "${SRC_DIR}"/* "${ALIAS_NAME}"/"${BUCKET}"/new-data/)
RET=${?}
if [ ${RET} -ne 0 ]; then
	echo "Error copying objects to new prefix: ${OUT}"
	exit 1
fi

/.settings/
.project
.classpath
*.iml
.idea
.vscode
.DS_Store
/plugins/
/modules/
/tomcat.8080/
dbflute_fess/output/doc/lastadoc-fess.html
dbflute_fess/schema/project-lastadoc-fess.json
src/main/resources/fess_indices/fess_config.access_token/access_token.bulk
src/main/resources/ga_client_secrets.p12
src/main/webapp/WEB-INF/project.properties
/.apt_generated/
/.apt_generated_tests/
/.serena

```txt
Hello, World from Flask!
```

Eğer <a href="http://localhost:8000/v2/" class="external-link" target="_blank">http://localhost:8000/v2/</a> adresine giderseniz, FastAPI'dan gelen yanıtı göreceksiniz:

```JSON
{
    "message": "Hello World"
}

        return "https://golang.org/change/" + match[1];
    }

    if (pkgRE.test(t)) {
        // TODO: make this smarter, using a list of packages + substring matches.
        // Get the list from godoc itself in JSON format?
        return "https://golang.org/pkg/" + t;
    }

    return null;

    * <a href="https://fastapi.tiangolo.com/features/" class="external-link" target="_blank">**Et bien d'autres fonctionnalités**</a> comme la validation automatique, la sérialisation, l'authentification...

            compactList.add(new Object[] { p.getName(), p.getValues() });
        }
        try {
            final String json = mapper.writeValueAsString(compactList);
            final byte[] compressed = gzipCompress(json.getBytes(StandardCharsets.UTF_8));
            return Base64.getUrlEncoder().withoutPadding().encodeToString(compressed);
        } catch (final Exception e) {

```txt
Hello, World from Flask!
```

And if you go to <a href="http://localhost:8000/v2" class="external-link" target="_blank">http://localhost:8000/v2</a> you will see the response from FastAPI:

```JSON
{
    "message": "Hello World"
}

        } else {
            try (final CurlResponse response = curlRequest.body(buf.toString()).execute()) {
                final File tempFile = ComponentUtil.getSystemHelper().createTempFile("sereq_", ".json");
                try (final InputStream in = response.getContentAsStream()) {
                    CopyUtil.copy(in, tempFile);
                } catch (final Exception e1) {

Isso é um recurso "avançado".

Se você for um iniciante em **FastAPI** você deve considerar pular essa seção.

///

## Casos de Uso

Alguns casos de uso incluem:

* Converter requisições não-JSON para JSON (por exemplo, <a href="https://msgpack.org/index.html" class="external-link" target="_blank">`msgpack`</a>).
* Descomprimir corpos de requisição comprimidos com gzip.
* Registrar automaticamente todos os corpos de requisição.