The **FastAPI** specific code is as small as always.

## ORMs

**FastAPI** works with any database and any style of library to talk to the database.

A common pattern is to use an "ORM": an "object-relational mapping" library.

An ORM has tools to convert ("*map*") between *objects* in code and database tables ("*relations*").

To do this, use `yield` instead of `return`, and write the extra steps (code) after.

!!! tip
    Make sure to use `yield` one single time.

!!! note "Technical Details"
    Any function that is valid to use with:

    ```

=== "Python 3.10+ non-Annotated"

    !!! tip
        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="7"
    {!> ../../../docs_src/dependencies/tutorial001_py310.py!}
    ```

=== "Python 3.8+ non-Annotated"

    !!! tip
        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="11"

The key features are:

* **Fast**: Very high performance, on par with **NodeJS** and **Go** (thanks to Starlette and Pydantic). [One of the fastest Python frameworks available](#performance).
* **Fast to code**: Increase the speed to develop features by about 200% to 300%. *
* **Fewer bugs**: Reduce about 40% of human (developer) induced errors. *

As environment variables can be set outside of the code, but can be read by the code, and don't have to be stored (committed to `git`) with the rest of the files, it's common to use them for configurations or settings.

You can also create an environment variable only for a specific program invocation, that is only available to that program, and only for its duration.

To do that, create it right before the program itself, on the same line:

<div class="termy">

### Krok 4: zdefiniuj **funkcję obsługującą ścieżkę**

To jest nasza "**funkcja obsługująca ścieżkę**":

* **ścieżka**: to `/`.
* **operacja**: to `get`.
* **funkcja**: to funkcja poniżej "dekoratora" (poniżej `@app.get("/")`).

```Python hl_lines="7"
{!../../../docs_src/first_steps/tutorial001.py!}
```

Jest to funkcja Python.

    This only shows the actual translated files, not the placeholders created with
    build-all.

    Takes an optional LANG argument with the name of the language to serve, by default
    en.
    """
    # Enable line numbers during local development to make it easier to highlight
    os.environ["LINENUMS"] = "true"
    if lang is None:
        lang = "en"
    lang_path: Path = docs_path / lang
    os.chdir(lang_path)

    path_values, path_errors = request_params_to_args(
        dependant.path_params, request.path_params
    )
    query_values, query_errors = request_params_to_args(
        dependant.query_params, request.query_params
    )
    header_values, header_errors = request_params_to_args(
        dependant.header_params, request.headers
    )
    cookie_values, cookie_errors = request_params_to_args(

    user_data = response.json()
    item_to_check = [it for it in user_data["items"] if it["id"] == item_data["id"]][0]
    assert item_to_check["title"] == item["title"]
    assert item_to_check["description"] == item["description"]
    response = client.get("/users/1")
    assert response.status_code == 200, response.text
    user_data = response.json()

    user_data = response.json()
    item_to_check = [it for it in user_data["items"] if it["id"] == item_data["id"]][0]
    assert item_to_check["title"] == item["title"]
    assert item_to_check["description"] == item["description"]
    response = client.get("/users/1")
    assert response.status_code == 200, response.text
    user_data = response.json()