这不是 **FastAPI** 的限制，而是 HTTP 协议的一部分。

///

## 可选文件上传 { #optional-file-upload }

你可以通过使用标准类型注解并将 `None` 作为默认值的方式将一个文件参数设为可选:

{* ../../docs_src/request_files/tutorial001_02_an_py310.py hl[9,17] *}

## 带有额外元数据的 `UploadFile` { #uploadfile-with-additional-metadata }

你也可以将 `File()` 与 `UploadFile` 一起使用，例如，设置额外的元数据:

    @Size(max = 10)
    public String searchFileProxy;

    /** Enable or disable using browser locale for search. */
    @Size(max = 10)
    public String searchUseBrowserLocale;

    /** SSO type (none, oic, saml, spnego, entraid). */
    @Size(max = 100)
    public String ssoType;

    /** User agent string for crawling operations. */
    @Size(max = 1000)
    public String crawlingUserAgent;

            Files.createFile(targetFile);

            // First delete succeeds
            assertTrue(Files.deleteIfExists(targetFile));

            // Second delete returns false (file already gone)
            assertFalse(Files.deleteIfExists(targetFile));
        } finally {
            deleteDirectory(tempDir.toFile());
        }
    }

allocated by C.  The most important consideration is not to
constrain future implementations, so the rule is that Go code can
hand a Go pointer to C code but must separately arrange for
Go to hang on to a reference to the pointer until C is done with it.
*/
package gmp

/*
#cgo LDFLAGS: -lgmp
#include <gmp.h>
#include <stdlib.h>

// gmp 5.0.0+ changed the type of the 3rd argument to mp_bitcnt_t,

 * Implementation detail for the internal structure of {@link Range} instances. Represents a unique
 * way of "cutting" a "number line" (actually of instances of type {@code C}, not necessarily
 * "numbers") into two sections; this can be done below a certain value, above a certain value,
 * below all values or above all values. With this object defined in this way, an interval can
 * always be represented by a pair of {@code Cut} instances.
 *

     * abstracts the access so far, that Oracle JDK, Open JDK and IBM JDK are
     * supported.
     *
     * At the time of the first implementation only a test on Oracle JDK was
     * done.
     */

    private static final String OPENJDK_JGSS_INQUIRE_TYPE_CLASS = "com.sun.security.jgss.InquireType";
    private static final String OPENJDK_JGSS_EXT_GSSCTX_CLASS = "com.sun.security.jgss.ExtendedGSSContext";

예를 들어, 경로 매개변수 `item_id`에 `title` 메타데이터 값을 선언하려면 다음과 같이 입력할 수 있습니다:

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[10] *}

/// note | 참고

경로 매개변수는 경로의 일부여야 하므로 언제나 필수입니다. `None`으로 선언하거나 기본값을 지정하더라도 아무 영향이 없으며, 항상 필수입니다.

///

## 필요한 대로 매개변수 정렬하기 { #order-the-parameters-as-you-need }

/// tip | 팁

`Annotated`를 사용한다면 이것은 아마 그렇게 중요하지 않거나 필요하지 않을 수 있습니다.

///

print(f"Hello {name} from Python")
```

/// tip | Dica

O segundo argumento para [`os.getenv()`](https://docs.python.org/3.8/library/os.html#os.getenv) é o valor padrão a ser retornado.

Se não for fornecido, é `None` por padrão, Aqui fornecemos `"World"` como o valor padrão a ser usado.

///

Então você poderia chamar esse programa Python:

//// tab | Linux, macOS, Windows Bash

<div class="termy">

```console

你可以声明与 `Query` 相同的所有参数。

例如，要为路径参数 `item_id` 声明 `title` 元数据值，你可以这样写：

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[10] *}

/// note | 注意

路径参数总是必需的，因为它必须是路径的一部分。即使你将其声明为 `None` 或设置了默认值，也不会产生任何影响，它依然始终是必需参数。

///

## 按需对参数排序 { #order-the-parameters-as-you-need }

/// tip | 提示

如果你使用 `Annotated`，这点可能不那么重要或必要。

///

假设你想要将查询参数 `q` 声明为必需的 `str`。

        .receivedResponseAtMillis(System.currentTimeMillis())
        .build()
        .also {
          chain.eventListener.satisfactionFailure(call, it)
        }
    }

    // If we don't need the network, we're done.
    if (networkRequest == null) {
      return cacheResponse!!
        .newBuilder()
        .cacheResponse(cacheResponse.stripBody())
        .build()
        .also {
          chain.eventListener.cacheHit(call, it)