Many of the tutorials have blocks of code.

In most of the cases, these blocks of code are actual complete applications that can be run as is.

In fact, those blocks of code are not written inside the Markdown, they are Python files in the `./docs_src/` directory.

And those Python files are included/injected in the documentation when generating the site.

### Docs for tests

* Add a **JSON Schema** for the response, in the OpenAPI *path operation*.
    * This will be used by the **automatic docs**.
    * It will also be used by automatic client code generation tools.

But most importantly:

* It will **limit and filter** the output data to what is defined in the return type.
    * This is particularly important for **security**, we'll see more of that below.

## `response_model` Parameter

## Previous tools

### <a href="https://www.djangoproject.com/" class="external-link" target="_blank">Django</a>

It's the most popular Python framework and is widely trusted. It is used to build systems like Instagram.

## Running on Startup

In most cases, when you create a web API, you want it to be **always running**, uninterrupted, so that your clients can always access it. This is of course, unless you have a specific reason why you want it to run only in certain situations, but most of the time you want it constantly running and **available**.

### In a Remote Server

* A `/items/{item_id}` _útvonalnak_ még van egy opcionális, `str` típusú _query paramétere_ is, a `q`.

### Interaktív API dokumentáció

Most nyisd meg a <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a> címet.

## Recap

Having **HTTPS** is very important, and quite **critical** in most cases. Most of the effort you as a developer have to put around HTTPS is just about **understanding these concepts** and how they work.

def get_top_users(
    *,
    counter: Counter,
    authors: Dict[str, Author],
    skip_users: Container[str],
    min_count: int = 2,
):
    users = []
    for commenter, count in counter.most_common(50):
        if commenter in skip_users:
            continue
        if count >= min_count:
            author = authors[commenter]
            users.append(
                {

## The main `FastAPI`

Now, let's see the module at `app/main.py`.

Here's where you import and use the class `FastAPI`.

This will be the main file in your application that ties everything together.

And as most of your logic will now live in its own specific module, the main file will be quite simple.

### Import `FastAPI`

You import and create a `FastAPI` class as normally.

* If you can't understand the question, ask for more **details**.

### Reproduce the problem

For most of the cases and most of the questions there's something related to the person's **original code**.

In many cases they will only copy a fragment of the code, but that's not enough to **reproduce the problem**.

...makes the parameter optional, with a default value of `None`, the same as:

```Python
q: str | None = None
```

But it declares it explicitly as being a query parameter.

!!! info
    Keep in mind that the most important part to make a parameter optional is the part:

    ```Python
    = None
    ```

    or the:

    ```Python
    = Query(default=None)
    ```