background: #d9515d;
    -webkit-box-shadow: 25px 0 0 #f4c025, 50px 0 0 #3ec930;
            box-shadow: 25px 0 0 #f4c025, 50px 0 0 #3ec930;
}

[data-termynal]:after {
    content: 'bash';
    position: absolute;
    color: var(--color-text-subtle);
    top: 5px;
    left: 0;
    width: 100%;
    text-align: center;
}

a[data-terminal-control] {

* Automatic data model documentation with <a href="https://json-schema.org/" class="external-link" target="_blank"><strong>JSON Schema</strong></a> (as OpenAPI itself is based on JSON Schema).
* Designed around these standards, after a meticulous study. Instead of an afterthought layer on top.
* This also allows using automatic **client code generation** in many languages.

### Automatic docs

<a href="https://platform.sh/try-it-now/?utm_source=fastapi-signup&utm_medium=banner&utm_campaign=FastAPI-signup-June-2023" target="_blank" title="Build, run and scale your apps on a modern, reliable, and secure PaaS."><img src="https://fastapi.tiangolo.com/img/sponsors/platform-sh.png"></a>

Then, near the end of the `Dockerfile`, we copy all the code. As this is what **changes most frequently**, we put it near the end, because almost always, anything after this step will not be able to use the cache.

```Dockerfile
COPY ./app /code/app
```

### Build the Docker Image

Now that all the files are in place, let's build the container image.

    # TODO: remove after upgrading SQLAlchemy to a version that includes the following changes
    # https://github.com/sqlalchemy/sqlalchemy/commit/59521abcc0676e936b31a523bd968fc157fef0c2
    'ignore:datetime\.datetime\.utcfromtimestamp\(\) is deprecated and scheduled for removal in a future version\..*:DeprecationWarning:sqlalchemy',

And it will work and will be useful **during development**.

But if your connection to the server is lost, the **running process** will probably die.

And if the server is restarted (for example after updates, or migrations from the cloud provider) you probably **won't notice it**. And because of that, you won't even know that you have to restart the process manually. So, your API will just stay dead. 😱

    item = data[item_id]
    if item["owner"] != username:
        raise OwnerError(username)
    return item
```

---

Before FastAPI 0.106.0, raising exceptions after `yield` was not possible, the exit code in dependencies with `yield` was executed *after* the response was sent, so [Exception Handlers](https://fastapi.tiangolo.com/tutorial/handling-errors/#install-custom-exception-handlers) would have already run.

    If you don't want to have those optional dependencies, you can instead install `pip install fastapi-slim`.

## Advanced User Guide

There is also an **Advanced User Guide** that you can read later after this **Tutorial - User guide**.

The **Advanced User Guide**, builds on this, uses the same concepts, and teaches you some extra features.

But you should first read the **Tutorial - User Guide** (what you are reading right now).