max_length: Optional[int] = None,
        pattern: Optional[str] = None,
        regex: Annotated[
            Optional[str],
            deprecated(
                "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
            ),
        ] = None,
        discriminator: Union[str, None] = None,
        strict: Union[bool, None] = _Unset,
        multiple_of: Union[float, None] = _Unset,

    regex: Annotated[
        Optional[str],
        Doc(
            """
            RegEx pattern for strings.
            """
        ),
        deprecated(
            "Deprecated in FastAPI 0.100.0 and Pydantic v2, use `pattern` instead."
        ),
    ] = None,
    discriminator: Annotated[
        Union[str, None],
        Doc(
            """

Aber wenn Sie sie brauchen und sie lernen, wissen Sie, dass Sie sie bereits direkt in **FastAPI** verwenden können.

### Pydantic v1 `regex` statt `pattern`

Vor Pydantic Version 2 und vor FastAPI Version 0.100.0, war der Name des Parameters `regex` statt `pattern`, aber das ist jetzt <abbr title="deprecated – obsolet, veraltet: Es soll nicht mehr verwendet werden">deprecated</abbr>.

* 🔧 Update the Question template to ask for the Pydantic version. PR [#10000](https://github.com/tiangolo/fastapi/pull/10000) by [@tiangolo](https://github.com/tiangolo).
* 📍 Update MkDocs Material dependencies. PR [#9986](https://github.com/tiangolo/fastapi/pull/9986) by [@tiangolo](https://github.com/tiangolo).

But whenever you need them and go and learn them, know that you can already use them directly in **FastAPI**.

### Pydantic v1 `regex` instead of `pattern`

Before Pydantic version 2 and before FastAPI 0.100.0, the parameter was called `regex` instead of `pattern`, but it's now deprecated.

You could still see some code using it:

=== "Python 3.10+ Pydantic v1"

    ```Python hl_lines="11"

                    <mxGeometry x="-60" y="-540" width="330" height="260" as="geometry"/>
                </mxCell>

                    <mxGeometry x="-60" y="-540" width="330" height="260" as="geometry"/>
                </mxCell>

                    <mxGeometry x="-60" y="-540" width="330" height="260" as="geometry"/>
                </mxCell>

                    <mxGeometry x="-60" y="-540" width="330" height="260" as="geometry"/>
                </mxCell>