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+"

  - 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.

* ⬆ Upgrade Swagger UI - swagger-ui-dist@4. This handles a security issue in Swagger UI itself where it could be possible to inject HTML into Swagger UI. Please upgrade as soon as you can, in particular if you expose your Swagger UI (`/docs`) publicly to non-expert users. PR [#4347](https://github.com/tiangolo/fastapi/pull/4347) by [@RAlanWright]...

## 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+"

COPY ./app /code/app

# (6)
CMD ["fastapi", "run", "app/main.py", "--port", "80"]
```

1. Start from the official Python base image.

2. Set the current working directory to `/code`.

    This is where we'll put the `requirements.txt` file and the `app` directory.

3. Copy the file with the requirements to the `/code` directory.

    Copy **only** the file with the requirements first, not the rest of the code.

This will be especially useful when you use it in a **large code base** where you use **the same dependencies** over and over again in **many *path operations***.

## To `async` or not to `async`

def decimal_encoder(dec_value: Decimal) -> Union[int, float]:
    """
    Encodes a Decimal as int of there's no exponent, otherwise float

    This is useful when we use ConstrainedDecimal to represent Numeric(x,0)
    where a integer (but not int typed) is used. Encoding this as a float
    results in failed round-tripping between encode and parse.
    Our Id type is a prime example of this.

    >>> decimal_encoder(Decimal("1.0"))
    1.0

## 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.