# Dependencies - `Depends()` and `Security()`

## `Depends()`

Dependencies are handled mainly with the special function `Depends()` that takes a callable.

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

    }
  }

  /**
   * Generates test cases for the given combination of scenario and timeouts. For methods that take
   * an explicit timeout value, all of the given timeoutsToUse result in individual test cases. For
   * methods that do not take an explicit timeout value, a single test case is generated only if the
   * implicit timeout of that method matches the given timeoutsToUse. For example, enter() is

{* ../../docs_src/security/tutorial002_an_py310.py hl[25] *}

## Get the user { #get-the-user }

`get_current_user` will use a (fake) utility function we created, that takes a token as a `str` and returns our Pydantic `User` model:

{* ../../docs_src/security/tutorial002_an_py310.py hl[19:22,26:27] *}

## Inject the current user { #inject-the-current-user }

```python
from fastapi import WebSocket
```

/// tip

When you want to define dependencies that should be compatible with both HTTP and WebSockets, you can define a parameter that takes an `HTTPConnection` instead of a `Request` or a `WebSocket`.

///

::: fastapi.WebSocket
    options:
        members:
            - scope
            - app
            - url
            - base_url

 * under the License.
 */
package org.apache.maven.artifact.resolver;

import javax.inject.Named;
import javax.inject.Singleton;

/**
 * Artifact collector - takes a set of original artifacts and resolves the best versions to use
 * along with their metadata. No artifacts are downloaded.
 */
@Deprecated
@Named
@Singleton

    }

    /**
     * Memoizes a given function that takes a String input and produces a String output.
     * This method creates a new function that caches the results of the original function,
     * improving performance for repeated calls with the same input.
     *
     * @param callback The original function to be memoized. It takes a String as input and returns a String.

  }

  // TODO(cpovirk): instead of skipping, use a smaller number of steps
  @GwtIncompatible // works but takes 5 minutes to run
  public void testPeekingIteratorBehavesLikeIteratorOnThreeElementIterable() {
    actsLikeIteratorHelper(Lists.newArrayList("A", "B", "C"));
  }

  @GwtIncompatible // works but takes 5 minutes to run
  public void testPeekingIteratorAcceptsNullElements() {

   * <p>This is identical to {@link #copy(Readable, Appendable)} but optimized for these specific
   * types. CharBuffer has poor performance when being written into or read out of so round tripping
   * all the bytes through the buffer takes a long time. With these specialized types we can just
   * use a char array.
   *
   * @param from the object to read from
   * @param to the object to write to
   * @return the number of characters copied

 * good" reference implementation. In order to accomplish this, it's important to test a great
 * variety of sequences of the {@link Iterator#next}, {@link Iterator#hasNext} and {@link
 * Iterator#remove} operations. This utility takes the brute-force approach of trying <i>all</i>
 * possible sequences of these operations, up to a given number of steps. So, if the caller
 * specifies to use <i>n</i> steps, a total of <i>3^n</i> tests are actually performed.
 *

   *   <li>Otherwise, return an instance of {@link ClusterException} that wraps the first exception
   *       in the {@code exceptions} collection.
   * </ul>
   *
   * <p>Though this method takes any {@link Collection}, it often makes most sense to pass a {@link
   * java.util.List} or some other collection that preserves the order in which the exceptions got
   * added.
   *
   * @throws NullPointerException if {@code exceptions} is null