{!> ../../docs_src/request_files/tutorial001.py!}
```

////

/// info

`File` is a class that inherits directly from `Form`.

But remember that when you import `Query`, `Path`, `File` and others from `fastapi`, those are actually functions that return special classes.

///

/// tip

To declare File bodies, you need to use `File`, because otherwise the parameters would be interpreted as query parameters or body (JSON) parameters.

 * }</pre>
 *
 * <p>Note that the behavior of {@link Range#isEmpty()} and {@link Range#isConnected(Range)} may not
 * be as expected on discrete ranges. See the Javadoc of those methods for details.
 *
 * <p>For a {@link Set} whose contents are specified by a {@link Range}, see {@link ContiguousSet}.
 *
 * <p>See the Guava User Guide article on <a href=

/**
 * Provides utility methods for working with character streams.
 *
 * <p>Some of the methods in this class take arguments with a generic type of {@code Readable &
 * Closeable}. A {@link java.io.Reader} implements both of those interfaces. Similarly for {@code
 * Appendable & Closeable} and {@link java.io.Writer}.
 *
 * @author Chris Nokleberg
 * @author Bin Zhu
 * @author Colin Decker
 * @since 1.0
 */
@J2ktIncompatible

 * @since 20.0
 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public final class PairedStatsAccumulator {

  // These fields must satisfy the requirements of PairedStats' constructor as well as those of the
  // stat methods of this class.
  private final StatsAccumulator xStats = new StatsAccumulator();
  private final StatsAccumulator yStats = new StatsAccumulator();
  private double sumOfProductsOfDeltas = 0.0;

...
```

#### What is OpenAPI for

The OpenAPI schema is what powers the two interactive documentation systems included.

And there are dozens of alternatives, all based on OpenAPI. You could easily add any of those alternatives to your application built with **FastAPI**.

You could also use it to generate code automatically, for clients that communicate with your API. For example, frontend, mobile or IoT applications.

   * across calls to multiple listeners. Specifically, a given listener will have its callbacks
   * invoked in the same order as the underlying service enters those states. Additionally, at most
   * one of the listener's callbacks will execute at once. However, multiple listeners' callbacks
   * may execute concurrently, and listeners may execute in an order different from the one in which

    // our test by setting a static field. We are changing the field in the parallel version of FRQ
    // and each test creates its own one of those, so there is no test interference here.
    Class<?> sepFrqSystemLoaderC =
        sepLoader.loadClass(FinalizableReferenceQueue.SystemLoader.class.getName());
    Field disabled = sepFrqSystemLoaderC.getDeclaredField("disabled");

We can use **OAuth2** to build that with **FastAPI**.

But let's save you the time of reading the full long specification just to find those little pieces of information you need.

Let's use the tools provided by **FastAPI** to handle security.

## How it looks

  }

  /**
   * Regression test for an edge case where closing response body in the HTTP engine doesn't release
   * the corresponding stream allocation. This test keeps those response bodies alive and reads
   * them after the redirect has completed. This forces a connection to not be reused where it would
   * be otherwise.
   *
   *
   * This test leaks a response body by not closing it.

  public boolean isCancelled() {
    return state.isCancelled();
  }

  @Override
  public boolean isDone() {
    return state.isDone();
  }

  /*
   * ForwardingFluentFuture needs to override those methods, so they are not final.
   */
  @CanIgnoreReturnValue
  @Override
  public V get() throws InterruptedException, ExecutionException {
    state.maybeThrowOnGet(throwable);
    return value;
  }