This is in contrast to the **development** stages, where you are constantly changing the code, breaking it and fixing it, stopping and restarting the development server, etc.

## Deployment Strategies

In an advanced scenario where you know you need the dependency to be called at every step (possibly multiple times) in the same request instead of using the "cached" value, you can set the parameter `use_cache=False` when using `Depends`:

=== "Python 3.8+"

# Extending OpenAPI

There are some cases where you might need to modify the generated OpenAPI schema.

In this section you will see how.

## The normal process

The normal (default) process, is as follows.

A `FastAPI` application (instance) has an `.openapi()` method that is expected to return the OpenAPI schema.

  - type: checkboxes
    id: help
    attributes:
      label: Commit to Help
      description: |
        After submitting this, I commit to one of:

          * Read open questions until I find 2 where I can help someone and add a comment to help there.
          * I already hit the "watch" button in this repository to receive notifications and I commit to help at least 2 people that ask questions in the future.

## Multiple models

Here's a general idea of how the models could look like with their password fields and the places where they are used:

=== "Python 3.10+"

    ```Python hl_lines="7  9  14  20  22  27-28  31-33  38-39"
    {!> ../../../docs_src/extra_models/tutorial001_py310.py!}
    ```

=== "Python 3.8+"

## Do not Separate Schemas

Now, there are some cases where you might want to have the **same schema for input and output**.

* Read the body of the request as JSON.
* Convert the corresponding types (if needed).
* Validate the data.
    * If the data is invalid, it will return a nice and clear error, indicating exactly where and what was the incorrect data.
* Give you the received data in the parameter `item`.

    You could pass a `dict`, a `list`, etc.

    They are handled automatically by **FastAPI** and converted to JSON.

## Add custom headers

There are some situations in where it's useful to be able to add custom headers to the HTTP error. For example, for some types of security.

You probably won't need to use it directly in your code.

    {!> ../../../docs_src/path_params_numeric_validations/tutorial005.py!}
    ```

## Number validations: floats, greater than and less than

Number validations also work for `float` values.