# About FastAPI versions

**FastAPI** is already being used in production in many applications and systems. And the test coverage is kept at 100%. But its development is still moving quickly.

New features are added frequently, bugs are fixed regularly, and the code is still continuously improving.

* You can then modify further the `response` before returning it.

```Python hl_lines="8-9  11  14"
{!../../../docs_src/middleware/tutorial001.py!}
```

!!! tip
    Keep in mind that custom proprietary headers can be added <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">using the 'X-' prefix</a>.

### Order of tags

The order of each tag metadata dictionary also defines the order shown in the docs UI.

For example, even though `users` would go after `items` in alphabetical order, it is shown before them, because we added their metadata as the first dictionary in the list.

## OpenAPI URL

By default, the OpenAPI schema is served at `/openapi.json`.

But you can configure it with the parameter `openapi_url`.

# See https://pre-commit.com/hooks.html for more hooks
default_language_version:
    python: python3.10
repos:
-   repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.4.0
    hooks:
    -   id: check-added-large-files
    -   id: check-toml
    -   id: check-yaml
        args:
        -   --unsafe
    -   id: end-of-file-fixer
    -   id: trailing-whitespace
-   repo: https://github.com/charliermarsh/ruff-pre-commit

    ```

=== "Python 3.8+"

    ```Python hl_lines="3  17"
    {!> ../../../docs_src/path_operation_configuration/tutorial001.py!}
    ```

That status code will be used in the response and will be added to the OpenAPI schema.

!!! note "Technical Details"
    You could also use `from starlette import status`.

def use_route_names_as_operation_ids(app: FastAPI) -> None:
    """
    Simplify operation IDs so that generated API clients have simpler function
    names.

    Should be called only after all routes have been added.
    """
    for route in app.routes:
        if isinstance(route, APIRoute):
            route.operation_id = route.name  # in this case, 'read_items'

    And as the `Response` can be used frequently to set headers and cookies, **FastAPI** also provides it at `fastapi.Response`.

## Custom Headers

Keep in mind that custom proprietary headers can be added <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">using the 'X-' prefix</a>.

  - type: checkboxes
    id: checks
    attributes:
      label: First Check
      description: Please confirm and check all the following options.
      options:
        - label: I added a very descriptive title here.
          required: true
        - label: I used the GitHub search to find a similar question and didn't find it.
          required: true

```

Here, the `shutdown` event handler function will write a text line `"Application shutdown"` to a file `log.txt`.

!!! info
    In the `open()` function, the `mode="a"` means "append", so, the line will be added after whatever is on that file, without overwriting the previous contents.

!!! tip
    Notice that in this case we are using a standard Python `open()` function that interacts with a file.

In that case, you can disable this feature in **FastAPI**, with the parameter `separate_input_output_schemas=False`.

!!! info
    Support for `separate_input_output_schemas` was added in FastAPI `0.102.0`. 🤓

=== "Python 3.10+"

    ```Python hl_lines="10"
    {!> ../../../docs_src/separate_openapi_schemas/tutorial002_py310.py!}
    ```

=== "Python 3.9+"