Using Linux containers has several advantages including **security**, **replicability**, **simplicity**, and others.

!!! tip
    In a hurry and already know this stuff? Jump to the [`Dockerfile` below 👇](#build-a-docker-image-for-fastapi).

<details>
<summary>Dockerfile Preview 👀</summary>

```Dockerfile
FROM python:3.9

WORKDIR /code

COPY ./requirements.txt /code/requirements.txt

## Technical Details

Modern versions of Python have support for **"asynchronous code"** using something called **"coroutines"**, with **`async` and `await`** syntax.

Let's see that phrase by parts in the sections below:

* **Asynchronous Code**
* **`async` and `await`**
* **Coroutines**

## Asynchronous Code

It will have a property `scopes` with a list containing all the scopes required by itself and all the dependencies that use this as a sub-dependency. That means, all the "dependants"... this might sound confusing, it is explained again later below.

The `security_scopes` object (of class `SecurityScopes`) also provides a `scope_str` attribute with a single string, containing those scopes separated by spaces (we are going to use it).

To understand more about it, see the section <a href="https://fastapi.tiangolo.com/benchmarks/" class="internal-link" target="_blank">Benchmarks</a>.

To understand more about it, see the section <a href="https://fastapi.tiangolo.com/benchmarks/" class="internal-link" target="_blank">Benchmarks</a>.

            ] = fastapi_specific_annotations[-1]
        else:
            fastapi_annotation = None
        if isinstance(fastapi_annotation, FieldInfo):
            # Copy `field_info` because we mutate `field_info.default` below.
            field_info = copy_field_info(
                field_info=fastapi_annotation, annotation=use_annotation
            )
            assert field_info.default is Undefined or field_info.default is Required, (

=== "Python 3.8+ alternative"

    ```Python hl_lines="1  4"
    {!> ../../../docs_src/python_types/tutorial009b.py!}
    ```

#### Sử dụng `Union` hay `Optional`

If you are using a Python version below 3.10, here's a tip from my very **subjective** point of view:

Nếu bạn đang sử dụng phiên bản Python dưới 3.10, đây là một mẹo từ ý kiến rất "chủ quan" của tôi:

* 🚨 Tránh sử dụng `Optional[SomeType]`