</div>

////

//// tab | `uv`

If you have <a href="https://github.com/astral-sh/uv" class="external-link" target="_blank">`uv`</a>:

<div class="termy">

```console
$ uv pip install "fastapi[standard]"
---> 100%
```

</div>

////

### Install from `requirements.txt` { #install-from-requirements-txt }

If you have a `requirements.txt`, you can now use it to install its packages.

In your production system, you probably have a frontend created with a modern framework like React, Vue.js or Angular.

And to communicate using WebSockets with your backend you would probably use your frontend's utilities.

Or you might have a native mobile application that communicates with your WebSocket backend directly, in native code.

Or you might have any other way to communicate with the WebSocket endpoint.

---

   * file. For discussion, see AbstractFutureState.
   */

  // Lazily initialized the first time we see an exception; not released until all the input futures
  // have completed and we have processed them all.
  volatile @Nullable Set<Throwable> seenExceptionsField = null;

  volatile int remainingField;

  private static final AtomicHelper ATOMIC_HELPER;

///

/// tip

Here we reuse the same Pydantic model.

But the same way, we could have validated it in some other way.

 * implementing {@code Map}, the additional type-safe operations {@link #putInstance} and {@link
 * #getInstance} are available.
 *
 * <p>Generally, implementations don't support {@link #put} and {@link #putAll} because there is no
 * way to check an object at runtime to be an instance of a {@link TypeToken}. Instead, caller
 * should use the type safe {@link #putInstance}.
 *

 * implementing {@code Map}, the additional type-safe operations {@link #putInstance} and {@link
 * #getInstance} are available.
 *
 * <p>Generally, implementations don't support {@link #put} and {@link #putAll} because there is no
 * way to check an object at runtime to be an instance of a {@link TypeToken}. Instead, caller
 * should use the type safe {@link #putInstance}.
 *

  @Override
  public ImmutableGraph<N> asGraph() {
    return new ImmutableGraph<>(this); // safe because the view is effectively immutable
  }

  private static <N, V> ImmutableMap<N, GraphConnections<N, V>> getNodeConnections(
      ValueGraph<N, V> graph) {
    // ImmutableMap.Builder maintains the order of the elements as inserted, so the map will have
    // whatever ordering the graph's nodes do, so ImmutableSortedMap is unnecessary even if the

Including external libraries also based on Pydantic, as <abbr title="Object-Relational Mapper">ORM</abbr>s, <abbr title="Object-Document Mapper">ODM</abbr>s for databases.

This also means that in many cases you can pass the same object you get from a request **directly to the database**, as everything is validated automatically.

  /**
   * Returns an immutable set of the values for the given key. If no mappings in the multimap have
   * the provided key, an empty immutable set is returned. The values are in the same order as the
   * parameters used to build this multimap.
   */
  @Override
  public ImmutableSet<V> get(K key) {
    // This cast is safe as its type is known in constructor.
    ImmutableSet<V> set = (ImmutableSet<V>) map.get(key);

  Throwable failureCause();

  /**
   * Registers a {@link Listener} to be {@linkplain Executor#execute executed} on the given
   * executor. The listener will have the corresponding transition method called whenever the
   * service changes state. The listener will not have previous state changes replayed, so it is
   * suggested that listeners are added before the service starts.
   *