# Dependencies { #dependencies }

**FastAPI** has a very powerful but intuitive **<abbr title="also known as components, resources, providers, services, injectables">Dependency Injection</abbr>** system.

It is designed to be very simple to use, and to make it very easy for any developer to integrate other components with **FastAPI**.

## What is "Dependency Injection" { #what-is-dependency-injection }

    return {"message": "Hello World"}
```

See the similarities in `requests.get(...)` and `@app.get(...)`.

/// check | Inspired **FastAPI** to

* Have a simple and intuitive API.
* Use HTTP method names (operations) directly, in a straightforward and intuitive way.
* Have sensible defaults, but powerful customizations.

///

In that case, the URL would be: `/files//home/johndoe/myfile.txt`, with a double slash (`//`) between `files` and `home`.

///

## Recap { #recap }

With **FastAPI**, by using short, intuitive and standard Python type declarations, you get:

* Editor support: error checks, autocompletion, etc.
* Data "<abbr title="converting the string that comes from an HTTP request into Python data">parsing</abbr>"

     | for profiles, such as 'env-dev', 'env-test', 'env-production', 'user-jdcasey', 'user-brett', etc.
     | This will make it more intuitive to understand what the set of introduced profiles is attempting
     | to accomplish, particularly when you only have a list of profile id's for debug.
     |

**Using `Annotated` is recommended** instead of the default value in function parameters, it is **better** for multiple reasons. 🤓

The **default** value of the **function parameter** is the **actual default** value, that's more intuitive with Python in general. 😌

It is based on <a href="https://www.python-httpx.org" class="external-link" target="_blank">HTTPX</a>, which in turn is designed based on Requests, so it's very familiar and intuitive.

With it, you can use <a href="https://docs.pytest.org/" class="external-link" target="_blank">pytest</a> directly with **FastAPI**.

## Using `TestClient` { #using-testclient }

/// info

### Summary { #summary }

I used to say I didn't like history that much... and look at me now giving "tech history" lessons. 😅

Und Abhängigkeiten können auf sehr einfache und intuitive Weise erstellt werden, sodass Sie einfach die benötigten Python-Packages importieren und sie in wenigen Codezeilen, *im wahrsten Sinne des Wortes*, mit Ihren API-Funktionen integrieren.

```

Sehen Sie sich die Ähnlichkeiten in `requests.get(...)` und `@app.get(...)` an.

/// check | Inspirierte **FastAPI**

* Über eine einfache und intuitive API zu verfügen.
* HTTP-Methodennamen (Operationen) direkt, auf einfache und intuitive Weise zu verwenden.
* Vernünftige Standardeinstellungen zu haben, aber auch mächtige Einstellungsmöglichkeiten.

///

///

### Editor support { #editor-support }

All the framework was designed to be easy and intuitive to use, all the decisions were tested on multiple editors even before starting development, to ensure the best development experience.