# Happy Pi Day! Google Home helps you learn the digits of Pi

> Celebrate Pi Day by learning how to build a Google Home assistant that tells you any digit of Pi using Cloud Functions and API.AI.

Author: [Guillaume Laforge](https://glaforge.dev/) | Published: 2017-03-14 | Topics: actions-on-google, google-cloud | Canonical: https://glaforge.dev/posts/2017/03/14/happy-pi-day-google-home-helps-you-learn-the-digits-of-pi/


You know what? It's Pi Day today! Well, if you follow the American date standard, it's 3.14 today, a nice approximation of Pi. Last year, in a past life, I had [played with Pi](http://restlet.com/company/blog/2016/03/14/win-a-raspberry-pi-3-to-celebrate-pi-day-with-a-pi-api/) already, but this year, my awesome colleagues ([Ray](https://twitter.com/saturnism), [Sandeep](https://twitter.com/SandeepDinesh), [Francesc](https://twitter.com/francesc), [Ian](https://twitter.com/IanMLewis)) have been working on some very cool demos around Pi, with the "Pi delivery", at <https://pi.delivery/>

![](/img/pi-day/pi-delivery-music.png)

You can transform the Pi digits in a nice melody, show a D3.js based visualisation of the transitions between digits, you can stream the Pi digits, and more. And you can learn about how it's been [developed on the Google Cloud Platform](https://pi.delivery/#howcalculating-pi).

Ray pinged me to see if we could also create an assistant you can invoke on Google Home, to ask for digits of Pi, as I recently played with [Google Home, API.AI and Cloud Functions](https://glaforge.dev/talks/2017/03/13/extending-the-google-assistant-with-actions-on-google/)! And I played with the idea: created a new Cloud Function that invokes the Pi's Web API, designed an assistant in API.AI, and submitted this assistant to the Google Assistant.

You'll be able to ask your Google Home:

> [!INFO] Example Interaction
> Ok Google, talk to Pi Digit Agent.
> What is the 34th digit of Pi?

And it will tell you that it's 2.

How did I do that, let's first have a look at the Cloud Function, implemented in JavaScript / Node.js:

```json
{
  "name": "pi-assistant",
  "version": "0.0.1",
  "private": true,
  "scripts": {
    "start": "node index.js",
    "deploy": "rm -rf node_modules; gcloud alpha functions deploy digit --project digit-of-pi-2017-assistant  --trigger-http --stage-bucket gs://digit-of-pi-2017-assistant/"
  },
  "description": "Ask for the n-th digit of Pi!",
  "main": "index.js",
  "repository": "",
  "author": "Guillaume Laforge",
  "dependencies": {
    "actions-on-google": "^1.0.7",
    "node-fetch": "^1.6.3"
  }
}
```

The key things here are the dependencies: I'm using the actions-on-google Node module to interact more easily with API.AI and the Assistant, and I'm using node-fetch to interact with the Pi Delivery's REST API.

Let's now have a look at the code of our exported digit function in index.js:

```javascript
const ApiAiAssistant = require('actions-on-google').ApiAiAssistant;
const fetch = require('node-fetch');
​
function nthDigit(assistant) {
    let rank = parseInt(assistant.getArgument('rank').replace(/,/g, ''));
    console.log(`${rank}nth digit`);
​
    // 0 -> 3, 1 -> ., 2 -> 1, 3 -> 4, 4 -> 1, ...
    // let's return 3 for 0th / 1st, and the digit otherwise, 
    // to follow natural human numbering and the fact the dot is accounted
​
    let start = rank < 2 ? 0 : rank;
​
    fetch(`https://api.pi.delivery/v1/pi?start=${start}&numberOfDigits=1`)
        .then(response => response.json())
        .then(data => {
            assistant.ask(`Digit ${rank} of Pi is ${data.content}. Do you want to know a different digit of Pi? Or say cancel to exit.`);
        }).catch(err => {
            console.log(err);
            assistant.ask('The ways of Pi are mysterious... Try again, or with another digit? Or say cancel to exit.');
        });
}
​
exports.digit = function (request, response) {
    let assistant = new ApiAiAssistant({request, response});
    let actionMap = new Map();
    actionMap.set('nth-digit-intent', nthDigit);
    assistant.handleRequest(actionMap);
};
```

It's pretty straightforward, we export a digit function, that creates an API.AI assistant, to which we feed an action map pointing at our main intent, for asking for digits. I extract the parameter (ie. the rank of the digit I'm interested in), I call the REST API with a fetch() call, and then I return the result with the assistant.ask() call.

In a nutshell, on API.AI's side, my welcome intent greets you, telling you how to use the assistant:

![](/img/pi-day/pi-welcome-intent.png)

And then the main intent, whose webhook points at my Cloud Function, does the heavy lifting:

![](/img/pi-day/pi-ask-digit-intent.png)

You can try it in the emulator:

![](/img/pi-day/pi-simulator.png)

After that, once the webhook is properly configured, I published my action, through the integrations pane, and the cloud API console. I'll skip the details here, but you can read more on [how to distribution your actions](https://developers.google.com/actions/distribute/).

So again, Happy Pi Day! And hopefully, if you have a Google Home device and when my assistant is officially published, you'll be able to learn more about the digits of Pi!

And let's finish with a video of the assistant running live on my Google Home!

{{< youtube JrqdhpSmNRc >}}