So, all these are different origins:

* `http://localhost`
* `https://localhost`
* `http://localhost:8080`

Even if they are all in `localhost`, they use different protocols or ports, so, they are different "origins".

## Steps

!!! info
    Beautiful illustrations by <a href="https://www.instagram.com/ketrinadrawsalot" class="external-link" target="_blank">Ketrina Thompson</a>. 🎨

---

Imagine you are the computer / program 🤖 in that story.

While you are at the line, you are just idle 😴, waiting for your turn, not doing anything very "productive". But the line is fast because the cashier is only taking the orders (not preparing them), so that's fine.

        What Python version are you using?

        You can find the Python version with:

        ```bash
        python --version
        ```
    validations:
      required: true
  - type: textarea
    id: context
    attributes:
      label: Additional Context

COPY ./app /app/app
```

### When to Use

You should probably **not** use this official base image (or any other similar one) if you are using **Kubernetes** (or others) and you are already setting **replication** at the cluster level, with multiple **containers**. In those cases, you are better off **building an image from scratch** as described above: [Build a Docker Image for FastAPI](#build-a-docker-image-for-fastapi).

    Because Pewee doesn't play well with anything async and there are better alternatives, I won't update these docs for Pydantic v2, they are kept for now only for historical purposes.

    The examples here are no longer tested in CI (as they were before).

If you are starting a project from scratch, you are probably better off with SQLAlchemy ORM ([SQL (Relational) Databases](../tutorial/sql-databases.md){.internal-link target=_blank}), or any other async ORM.

## About third party integrations

In this example we are using the OAuth2 "password" flow.

This is appropriate when we are logging in to our own application, probably with our own frontend.

Because we can trust it to receive the `username` and `password`, as we control it.

### Return the error

After detecting that the credentials are incorrect, return an `HTTPException` with a status code 401 (the same returned when no credentials are provided) and add the header `WWW-Authenticate` to make the browser show the login prompt again:

=== "Python 3.9+"

    ```Python hl_lines="26-30"

!!! info
    In Pydantic version 1 the method to get the JSON Schema for a model was called `Item.schema()`, in Pydantic version 2, the method is called `Item.model_json_schema()`.

Nevertheless, although we are not using the default integrated functionality, we are still using a Pydantic model to manually generate the JSON Schema for the data that we want to receive in YAML.

    When you return a `Response` directly, like in the example above, it will be returned directly.

    It won't be serialized with a model, etc.

    Make sure it has the data you want it to have, and that the values are valid JSON (if you are using `JSONResponse`).

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

Now let's build from the previous chapter and add the missing parts to have a complete security flow.

## Get the `username` and `password`

We are going to use **FastAPI** security utilities to get the `username` and `password`.

OAuth2 specifies that when using the "password flow" (that we are using) the client/user must send a `username` and `password` fields as form data.