---

"_**FastAPI** için ayın üzerindeymişcesine heyecanlıyım. Çok eğlenceli!_"

<div style="text-align: right; margin-right: 10%;">Brian Okken - <strong><a href="https://pythonbytes.fm/episodes/show/123/time-to-right-the-py-wrongs?time_in_sec=855" target="_blank">Python Bytes</a> podcast host</strong> <a href="https://twitter.com/brianokken/status/1112220079972728832" target="_blank"><small>(ref)</small></a></div>

---

---

"_I’m over the moon excited about **FastAPI**. It’s so fun!_"

<div style="text-align: right; margin-right: 10%;">Brian Okken - <strong><a href="https://pythonbytes.fm/episodes/show/123/time-to-right-the-py-wrongs?time_in_sec=855" target="_blank">Python Bytes</a> podcast host</strong> <a href="https://twitter.com/brianokken/status/1112220079972728832" target="_blank"><small>(ref)</small></a></div>

---

github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=

---

"_Je suis très enthousiaste à propos de **FastAPI**. C'est un bonheur !_"

<div style="text-align: right; margin-right: 10%;">Brian Okken - <strong>Auteur du podcast <a href="https://pythonbytes.fm/episodes/show/123/time-to-right-the-py-wrongs?time_in_sec=855" target="_blank">Python Bytes</a></strong> <a href="https://twitter.com/brianokken/status/1112220079972728832" target="_blank"><small>(ref)</small></a></div>

---

Go to the *path operation* "Get `/slowusers/`" in all of the tabs. Use the "Try it out" button and execute the request in each tab, one right after the other.

The tabs will wait for a bit and then some of them will show `Internal Server Error`.

### What happens

The first tab will make your app create a connection to the database and wait for some seconds before replying back and closing the database connection.

---

"_👤 🤭 🌕 😄 🔃 **FastAPI**. ⚫️ 🎊 ❗_"

<div style="text-align: right; margin-right: 10%;">✡ 🇭🇰 - <strong><a href="https://pythonbytes.fm/episodes/show/123/time-to-right-the-py-wrongs?time_in_sec=855" target="_blank">🐍 🔢</a> 📻 🦠</strong> <a href="https://twitter.com/brianokken/status/1112220079972728832" target="_blank"><small>(🇦🇪)</small></a></div>

---

    {!> ../../../docs_src/dependencies/tutorial011.py!}
    ```

!!! tip
    All this might seem contrived. And it might not be very clear how is it useful yet.

    These examples are intentionally simple, but show how it all works.

    In the chapters about security, there are utility functions that are implemented in this same way.

These dependencies will be executed/solved the same way as normal dependencies. But their value (if they return any) won't be passed to your *path operation function*.

!!! tip
    Some editors check for unused function parameters, and show them as errors.

    Using these `dependencies` in the *path operation decorator* you can make sure they are executed while avoiding editor/tooling errors.

# help works by looking over all Makefile includes matching `target: ## comment` regex and outputting them
help: ## Show this help
	@egrep -h '^[a-zA-Z_\.-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort  | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-20s\033[0m %s\n", $$1, $$2}'

So, what we will do next is add the code to document how that *external API* should look like to receive the callback from *your API*.

That documentation will show up in the Swagger UI at `/docs` in your API, and it will let external developers know how to build the *external API*.

This example doesn't implement the callback itself (that could be just a line of code), only the documentation part.