That defines the metadata about the main response of a *path operation*.

You can also declare additional responses with their models, status codes, etc.

There's a whole chapter here in the documentation about it, you can read it at [Additional Responses in OpenAPI](additional-responses.md){.internal-link target=_blank}.

## OpenAPI Extra

        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {
            "/users/": {
                "get": {
                    "tags": ["users"],
                    "summary": "Read Users",
                    "operationId": "read_users_users__get",
                    "parameters": [
                        {
                            "required": True,

        String INITIALIZE = "initialize";
        String VALIDATE = "validate";
        String SOURCES = "sources";
        String RESOURCES = "resources";
        String COMPILE = "compile";
        String READY = "ready";
        String PACKAGE = "package";
        String VERIFY = "verify";
        String UNIT_TEST = "unit-test";
        String TEST_SOURCES = "test-sources";
        String TEST_RESOURCES = "test-resources";

The same models are shared among requests, so, it's not one model per request, or one per user or something similar.

Let's imagine that loading the model can **take quite some time**, because it has to read a lot of **data from disk**. So you don't want to do it for every request.

* `write(data)`：把 `data` （`str` 或 `bytes`）写入文件；
* `read(size)`：按指定数量的字节或字符（`size` (`int`)）读取文件内容；
* `seek(offset)`：移动至文件 `offset` （`int`）字节处的位置；
    * 例如，`await myfile.seek(0) ` 移动到文件开头；
    * 执行 `await myfile.read()` 后，需再次读取已读取内容时，这种方法特别好用；
* `close()`：关闭文件。

因为上述方法都是 `async` 方法，要搭配「await」使用。

例如，在 `async` *路径操作函数* 内，要用以下方式读取文件内容：

```Python
contents = await myfile.read()
```

            digest.sign( dst, headerStart, length, this, response );
        }

        return length;
    }

    /*
     * We overload this because we want readAndXWireFormat to
     * read the parameter words and bytes. This is so when
     * commands are batched together we can recursivly call
     * readAndXWireFormat without reading the non-existent header.
     */

        return null;
    }

    private String getError(File touchFile, String key) {
        Properties props = read(touchFile);
        if (props != null) {
            return props.getProperty(key + ERROR_KEY_SUFFIX);
        }
        return null;
    }

    private Properties read(File touchfile) {
        if (!touchfile.canRead()) {

                                    }
                                }
                            },
                        },
                    },
                    "summary": "Read Items",
                    "operationId": "read_items_items__get",
                    "parameters": [
                        {
                            "required": False,
                            "schema": IsDict(

    assertThat(body.bytes()).isEqualTo(text)
  }
}

abstract class ForwardingSource(
  val delegate: Source,
) : Source {
  override fun read(
    sink: Buffer,
    byteCount: Long,
  ): Long = delegate.read(sink, byteCount)

  override fun timeout() = delegate.timeout()

  override fun close() = delegate.close()

                                    }
                                }
                            },
                        },
                    },
                    "summary": "Read Items",
                    "operationId": "read_items_items__get",
                    "parameters": [
                        {
                            "required": False,
                            "schema": IsDict(