# 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()`

    @JvmStatic
    @JvmName("parse")
    fun String.toMediaTypeOrNull(): MediaType? = commonToMediaTypeOrNull()

    @JvmName("-deprecated_get")
    @Deprecated(
      message = "moved to extension function",
      replaceWith =
        ReplaceWith(
          expression = "mediaType.toMediaType()",
          imports = ["okhttp3.MediaType.Companion.toMediaType"],
        ),
      level = DeprecationLevel.ERROR,

 * limitations under the License.
 */

package com.google.common.collect;

import static java.util.Arrays.asList;

import com.google.common.base.Function;
import com.google.common.collect.testing.SafeTreeSet;
import com.google.common.collect.testing.SortedSetTestSuiteBuilder;
import com.google.common.collect.testing.TestStringSortedSetGenerator;

So, if you run this example and go to <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>, you will see a response of:

```JSON
{"item_id":"foo"}
```

## Path parameters with types

You can declare the type of a path parameter in the function, using standard Python type annotations:

   *
   * @throws NullPointerException if the function returns {@code null}
   * @since 12.0
   */
  public abstract <V> Optional<V> transform(Function<? super T, V> function);

  /**
   * Returns {@code true} if {@code object} is an {@code Optional} instance, and either the
   * contained references are {@linkplain Object#equals equal} to each other or both are absent.

 * limitations under the License.
 */

package com.google.common.collect;

import static java.util.Arrays.asList;

import com.google.common.base.Function;
import com.google.common.collect.testing.MinimalSet;
import com.google.common.collect.testing.SetTestSuiteBuilder;
import com.google.common.collect.testing.TestStringSetGenerator;

So, the section with:

{% raw %}

```jinja
<a href="{{ url_for('read_item', id=id) }}">
```

{% endraw %}

...will generate a link to the same URL that would be handled by the *path operation function* `read_item(id=id)`.

For example, with an ID of `42`, this would render:

```html

# `UploadFile` class

You can define *path operation function* parameters to be of the type `UploadFile` to receive files from the request.

You can import it directly from `fastapi`:

```python
from fastapi import UploadFile
```

::: fastapi.UploadFile
    options:
        members:
            - file
            - filename
            - size
            - headers
            - content_type
            - read

8. Notice that this *path operation function* uses regular `def` instead of `async def`.

    As always, in FastAPI you can combine `def` and `async def` as needed.

    If you need a refresher about when to use which, check out the section _"In a hurry?"_ in the docs about [`async` and `await`](../async.md#in-a-hurry){.internal-link target=_blank}.

    "price": 42.0,
    "tax": 3.2
}
```

## Recap

You can add multiple body parameters to your *path operation function*, even though a request can only have a single body.

But **FastAPI** will handle it, give you the correct data in your function, and validate and document the correct schema in the *path operation*.

You can also declare singular values to be received as part of the body.