### 模拟文件 { #simulate-a-file }

在这个示例中，我们用 `io.BytesIO` 模拟了一个文件，它是只驻留在内存中的类文件对象，但提供相同的接口。

例如，我们可以像对文件那样迭代它来消费其内容。

{* ../../docs_src/stream_data/tutorial002_py310.py ln[1:27] hl[3,12:13,25] *}

/// note | 技术细节

另外两个变量 `image_base64` 和 `binary_image` 表示一张图像，先用 Base64 编码，再转换为 bytes，最后传给 `io.BytesIO`。

只是为了让它们能和示例放在同一个文件里，便于你直接复制运行。🥚

///

通过使用 `with` 代码块，我们确保在生成器函数（带有 `yield` 的函数）完成后关闭这个类文件对象。也就是在发送完响应之后。

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: bool | None = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: str | None = None):
    return {"item_id": item_id, "q": q}


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):

   *
   * <p>Note: the table assumes complete ownership over of {@code backingMap} and the maps returned
   * by {@code factory}. Those objects should not be manually updated and they should not use soft,
   * weak, or phantom references.
   *
   * @param backingMap place to store the mapping from each row key to its corresponding column key
   *     / value map

    public void test_unescapedPlusDoesNotMatch() {
        // Demonstrate the bug when + is not escaped
        // In regex, + means "one or more" of the previous character
        String wrongPattern = "(application/xhtml+xml|application/rdf+xml)";
        Pattern pattern = Pattern.compile(wrongPattern);

        // Without escaping, "application/xhtml+xml" does NOT match
        // because the pattern expects "one or more 'l'" followed by "xml"

   * unsigned {@code long} value in the specified radix.
   *
   * @throws NumberFormatException if the string does not contain a parsable unsigned {@code long}
   *     value, or {@code radix} is not between {@link Character#MIN_RADIX} and {@link
   *     Character#MAX_RADIX}
   */
  @CanIgnoreReturnValue
  public static UnsignedLong valueOf(String string, int radix) {

            description,
            cls,
            explicitTestNames.get(0),
            cls.getName());
    return new AssertionError(message, e);
  }

  /**
   * Finds the classes not ending with a test suffix and not covered by an explicit test whose name
   * is {@code explicitTestNames}.
   */
  @VisibleForTesting
  List<Class<?>> findClassesToTest(

import org.slf4j.LoggerFactory;

/**
 * Common code that is shared by the LifecycleModuleBuilder and the LifeCycleWeaveBuilder
 *
 * @since 3.0
 *         Builds one or more lifecycles for a full module
 *         NOTE: This class is not part of any public api and can be changed or deleted without prior notice.
 */
@Named
@Singleton
public class BuilderCommon {
    private final Logger logger;

    }

    @Override
    public CharMatcher negate() {
      return none();
    }
  }

  /** Implementation of {@link #none()}. */
  private static final class None extends NamedFastMatcher {

    static final CharMatcher INSTANCE = new None();

    private None() {
      super("CharMatcher.none()");
    }

    @Override
    public boolean matches(char c) {

    return try {
      // Attempt to get the trust manager from an OpenJDK socket factory. We attempt this on all
      // platforms in order to support Robolectric, which mixes classes from both Android and the
      // Oracle JDK. Note that we don't support HTTP/2 or other nice features on Robolectric.
      val sslContextClass = Class.forName("sun.security.ssl.SSLContextImpl")

 *    either peer may not have been transmitted to the other.
 *
 * Note that the state progression is independent for each peer. Arriving at a gracefully-closed
 * state indicates that a peer has sent all of its outgoing messages and received all of its
 * incoming messages. But it does not guarantee that the other peer will successfully receive all of
 * its incoming messages.
 *