# Exceptions – `HTTPException` und `WebSocketException`

Dies sind die <abbr title="Exception – Ausnahme, Fehler: Python-Objekt, das einen Fehler nebst Metadaten repräsentiert">Exceptions</abbr>, die Sie auslösen können, um dem Client Fehler zu berichten.

# Exceptions - `HTTPException` and `WebSocketException`

These are the exceptions that you can raise to show errors to the client.

When you raise an exception, as would happen with normal Python, the rest of the execution is aborted. This way you can raise these exceptions from anywhere in the code to abort a request and show the error to the client.

You can use:

* `HTTPException`
* `WebSocketException`

from pydantic import BaseModel, create_model
from starlette.exceptions import HTTPException as StarletteHTTPException
from starlette.exceptions import WebSocketException as StarletteWebSocketException
from typing_extensions import Annotated, Doc


class HTTPException(StarletteHTTPException):
    """
    An HTTP exception you can raise in your own code to show errors to the client.

def reset_state_and_db():
    global fake_database
    global state
    fake_database = initial_fake_database.copy()
    state = initial_state.copy()


client = TestClient(app)


def test_dependency_gets_exception():
    assert state["except"] is False
    assert state["finally"] is False
    response = client.put("/invalid-user/rick", json="Morty")
    assert response.status_code == 400, response.text

     *
     * @param exceptions the exceptions that occurred while building the dependency graph
     * @param root the root node of the dependency graph
     * @param count estimated number of dependencies
     */
    DefaultDependencyResolverResult(List<Exception> exceptions, Node root, int count) {
        this.exceptions = exceptions;
        this.root = root;
        nodes = new ArrayList<>(count);

    ```

An alternative you could use to catch exceptions (and possibly also raise another `HTTPException`) is to create a [Custom Exception Handler](../handling-errors.md#install-custom-exception-handlers){.internal-link target=_blank}.

## Dependencies with `yield` and `except`

 *       will be thrown.
 *   <li>If no exceptions or errors were thrown in the try block, the <i>first</i> exception thrown
 *       by an attempt to close a resource will be thrown.
 *   <li>Any exception caught when attempting to close a resource that is <i>not</i> thrown (because
 *       another exception is already being thrown) is <i>suppressed</i>.
 * </ul>
 *

     *
     * @param exceptions the exceptions that occurred while building the dependency graph
     * @param root the root node of the dependency graph
     * @param count estimated number of dependencies
     */
    DefaultDependencyResolverResult(List<Exception> exceptions, Node root, int count) {
        this.exceptions = exceptions;
        this.root = root;
        nodes = new ArrayList<>(count);

```

## Install custom exception handlers

You can add custom exception handlers with <a href="https://www.starlette.io/exceptions/" class="external-link" target="_blank">the same exception utilities from Starlette</a>.

Let's say you have a custom exception `UnicornException` that you (or a library you use) might `raise`.

And you want to handle this exception globally with FastAPI.

      // the operation would be a no-op, so exceptions are allowed but not required
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  public void testReplaceEntry_unsupportedAbsentKey() {
    try {
      getMap().replace(k3(), v3(), v4());
    } catch (UnsupportedOperationException tolerated) {
      // the operation would be a no-op, so exceptions are allowed but not required
    }