* Data "<abbr title="converting the string that comes from an HTTP request into Python data">parsing</abbr>"
* Data validation
* API annotation and automatic documentation

And you only have to declare them once.

            'Whitelist' validation step. The parameter field will be the single one
            allowed by the alias or set of aliases defined.
            """
        ),
    ] = None,
    serialization_alias: Annotated[
        Union[str, None],
        Doc(
            """
            'Blacklist' validation step. The vanilla parameter field will be the
            single one of the alias' or set of aliases' fields and all the other

In this case, it would be better to get **one extra server** and run some processes on it so that they all have **enough RAM and CPU time**.

    The current version assumes Pydantic v1.

    The new docs will include Pydantic v2 and will use <a href="https://sqlmodel.tiangolo.com/" class="external-link" target="_blank">SQLModel</a> once it is updated to use Pydantic v2 as well.

!!! warning "Deprecated"
    This tutorial is deprecated and will be removed in a future version.

-e .[all]
-r requirements-docs-tests.txt
pytest >=7.1.3,<8.0.0
coverage[toml] >= 6.5.0,< 8.0
mypy ==1.8.0
ruff ==0.2.0
dirty-equals ==0.6.0
# TODO: once removing databases from tutorial, upgrade SQLAlchemy
# probably when including SQLModel
sqlalchemy >=1.3.18,<1.4.43
databases[sqlite] >=0.3.2,<0.7.0
flask >=1.1.2,<3.0.0
anyio[trio] >=3.2.1,<4.0.0
python-jose[cryptography] >=3.3.0,<4.0.0
pyyaml >=5.3.1,<7.0.0
passlib[bcrypt] >=1.7.2,<2.0.0

Calling this program outputs:

```
John Doe
```

The function does the following:

* Takes a `first_name` and `last_name`.
* Converts the first letter of each one to upper case with `title()`.
* <abbr title="Puts them together, as one. With the contents of one after the other.">Concatenates</abbr> them with a space in the middle.

```Python hl_lines="2"
{!../../../docs_src/python_types/tutorial001.py!}
```

### Edit it

### Creating the `Settings` only once with `lru_cache`

Reading a file from disk is normally a costly (slow) operation, so you probably want to do it only once and then re-use the same settings object, instead of reading it for each request.

But every time we do:

```Python
Settings()
```

You can define logic (code) that should be executed before the application **starts up**. This means that this code will be executed **once**, **before** the application **starts receiving requests**.

The same way, you can define logic (code) that should be executed when the application is **shutting down**. In this case, this code will be executed **once**, **after** having handled possibly **many requests**.

It is used by many companies including Mozilla, Red Hat and Eventbrite.

It was one of the first examples of **automatic API documentation**, and this was specifically one of the first ideas that inspired "the search for" **FastAPI**.

!!! note

    username: username string. The OAuth2 spec requires the exact field name "username".
    password: password string. The OAuth2 spec requires the exact field name "password".
    scope: Optional string. Several scopes (each one a string) separated by spaces. E.g.
        "items:read items:write users:read profile openid"
    client_id: optional string. OAuth2 recommends sending the client_id and client_secret (if any)