Você pode definir uma <abbr title="Uma expressão regular, regex ou regexp é uma sequência de caracteres que define um parâmetro de busca para textos.">expressão regular</abbr> que combine com um padrão esperado pelo parâmetro:

```Python hl_lines="11"
{!../../../docs_src/query_params_str_validations/tutorial004.py!}
```

Essa expressão regular específica verifica se o valor recebido no parâmetro:

7. Here the `response_model` is using a type annotation of a list of `Author` dataclasses.

    Again, you can combine `dataclasses` with standard type annotations.

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.

    ```

=== "🐍 3️⃣.1️⃣0️⃣ & 🔛"

    ```Python hl_lines="7"
    {!> ../../../docs_src/query_params_str_validations/tutorial003_py310.py!}
    ```

## 🚮 🥔 🧬

👆 💪 🔬 <abbr title="A regular expression, regex or regexp is a sequence of characters that define a search pattern for strings.">🥔 🧬</abbr> 👈 🔢 🔜 🏏:

=== "🐍 3️⃣.6️⃣ &amp; 🔛"

    ```Python hl_lines="11"

    ```Python hl_lines="10"
    {!> ../../../docs_src/query_params_str_validations/tutorial003.py!}
    ```

## Add regular expressions

You can define a <abbr title="A regular expression, regex or regexp is a sequence of characters that define a search pattern for strings.">regular expression</abbr> `pattern` that the parameter should match:

=== "Python 3.10+"

    ```Python hl_lines="11"

        self,
        func: Annotated[
            Callable[P, Any],
            Doc(
                """
                The function to call after the response is sent.

                It can be a regular `def` function or an `async def` function.
                """
            ),
        ],
        *args: P.args,
        **kwargs: P.kwargs,
    ) -> None:
        """

            """
        ),
    ] = True,
) -> Any:
    """
    Declare a FastAPI Security dependency.

    The only difference with a regular dependency is that it can declare OAuth2
    scopes that will be integrated with OpenAPI and the automatic UI docs (by default
    at `/docs`).

    It takes a single "dependable" callable (like a function).

```

The code following the `yield` statement is executed after the response has been delivered:

```Python hl_lines="5-6"
{!../../../docs_src/dependencies/tutorial007.py!}
```

!!! tip
    You can use `async` or regular functions.

    **FastAPI** will do the right thing with each, the same as with normal dependencies.

## A dependency with `yield` and `try`

    typography:
      content: *page_description
      align: start
      color: *color
      line:
        amount: 2
        height: 1.5
      font:
        family: *font_family

That means: "the variable `items` is a `list`, and each of the items in this list is a `str`".

!!! tip
    If you use Python 3.9 or above, you don't have to import `List` from `typing`, you can use the same regular `list` type instead.

By doing that, your editor can provide support even while processing items from the list:

<img src="/img/python-types/image05.png">

Without types, that's almost impossible to achieve.

class UploadFile(StarletteUploadFile):
    """
    A file uploaded in a request.

    Define it as a *path operation function* (or dependency) parameter.

    If you are using a regular `def` function, you can use the `upload_file.file`
    attribute to access the raw standard Python file (blocking, not async), useful and
    needed for non-async code.

    Read more about it in the