"strict": strict,
                    "json_schema_extra": current_json_schema_extra,
                }
            )
            kwargs["pattern"] = pattern or regex
        else:
            kwargs["regex"] = pattern or regex
            kwargs.update(**current_json_schema_extra)
        use_kwargs = {k: v for k, v in kwargs.items() if v is not _Unset}

        super().__init__(**use_kwargs)

            """
        ),
    ] = None,
    pattern: Annotated[
        Optional[str],
        Doc(
            """
            RegEx pattern for strings.
            """
        ),
    ] = None,
    regex: Annotated[
        Optional[str],
        Doc(
            """
            RegEx pattern for strings.
            """
        ),
        deprecated(

        {
            "detail": [
                {
                    "type": "string_pattern_mismatch",
                    "loc": ["query", "item-query"],
                    "msg": "String should match pattern '^fixedquery$'",
                    "input": "nonregexquery",
                    "ctx": {"pattern": "^fixedquery$"},
                }
            ]
        }
    ) | IsDict(

                        "grant_type": IsDict(
                            {
                                "title": "Grant Type",
                                "anyOf": [
                                    {"pattern": "password", "type": "string"},
                                    {"type": "null"},
                                ],
                            }
                        )
                        | IsDict(

    know that that it is application specific, it's not part of the specification.
    """

    def __init__(
        self,
        *,
        grant_type: Annotated[
            Union[str, None],
            Form(pattern="password"),
            Doc(
                """
                The OAuth2 spec says it is required and MUST be the fixed string
                "password". Nevertheless, this dependency class is permissive and

def is_body_allowed_for_status_code(status_code: Union[int, str, None]) -> bool:
    if status_code is None:
        return True
    # Ref: https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.1.0.md#patterned-fields-1
    if status_code in {
        "default",
        "1XX",
        "2XX",
        "3XX",
        "4XX",
        "5XX",
    }:
        return True
    current_status_code = int(status_code)

You can use the same type declarations with `str`, `float`, `bool` and many other complex data types.

Several of these are explored in the next chapters of the tutorial.

## Order matters

When creating *path operations*, you can find situations where you have a fixed path.

Like `/users/me`, let's say that it's to get data about the current user.

    {!> ../../../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"
    {!> ../../../docs_src/query_params_str_validations/tutorial004.py!}
    ```

=== "🐍 3️⃣.1️⃣0️⃣ &amp; 🔛"

        {
            "detail": [
                {
                    "type": "string_pattern_mismatch",
                    "loc": ["body", "grant_type"],
                    "msg": "String should match pattern 'password'",
                    "input": "incorrect",
                    "ctx": {"pattern": "password"},
                }
            ]
        }
    ) | IsDict(

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>.