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Twilio SendGrid Day One: Building My Track Jacket App

sameer_jacket_hands.jpg

From the beginning, Twilio and SendGrid have both enshrined customer experience in their core values. SendGrid strives to be Humble and exemplify a customer-first mindset. Twilio encourages employees to Wear the customer’s shoes.

We live those values everyday. There’s a hallowed tradition here at Twilio: every Twilion who builds and demos a Twilio powered app earns their red track jacket. Working on an application from a customer’s perspective helps us truly build empathy for our users.

Today, as Twilio and SendGrid celebrated coming together as one company, I had the opportunity to demo my track jacket app. Using building blocks from Twilio and SendGrid I built an SMS responder which also emails a GIF using Python and the microframework Flask.

Let’s look at how it works so you can build your own.

Prerequisites for my SMS and Email Responder

To reproduce my code you’ll first need to sign up for (or log into) SendGrid and Twilio accounts:

You’ll also need Python 3.6 on your machine. My instructions are for Mac OSX, but should be similar if you have a comparable shell.

We’ll also need a publicly available endpoint to set as a Twilio webhook. You could deploy this application somewhere, but the easiest way to ‘go public’ is to install ngrok.

Build and Run a Python SMS and Email Responder

Once you have your accounts and Python and ngrok installed, you’re ready to get down to coding, running, and testing! Let’s begin by setting up a virtual environment and start installing packages.

Set Up a Python Development Environment

Start by creating a new project directory and virtual environment.

mkdir twilio-sendgrid && cd twilio-sendgrid
virtualenv -p python3 env
source env/bin/activate

Excellent – now you have an isolated virtual environment running. Everything you install using pip will only affect this local development environment, not your global setup.

Start by installing the twilio and sendgrid helper libraries:

pip install twilio
pip install sendgrid

You’ll also need to do email validation. It’s far easier to bring in a library for that – install validate_email to take care of that important step for us:

pip install validate_email

Grab Your SendGrid Credentials and a Twilio Phone Number

Before you can respond to incoming phone numbers you’ll need to grab a Twilio phone number. Navigate to the Buy a Number page in the console, check the "SMS" box, and click "Search."

When you see numbers returned, select your favorite and click “Buy”:

Buy a SMS capable Twilio number

Next, visit the API Keys page in the SendGrid console. Click the blue ‘Create API Key’ button in the upper right hand corner:

Create a SendGrid API Key button

Create a ‘Full Access’ key, and name it something funny.

Important: copy that key somewhere safe! You only get one chance; if you miss your chance to copy the key you’ll have to create a new one.

Excellent work – next we’ll design the email response we’ll be sending.

Create a SendGrid Email Template

SendGrid’s email template designer makes it simple to edit and preview the emails you’ll be sending with SendGrid.

Visit the Template page in your SendGrid console, and if prompted select the ‘Legacy Template’ button. Normally we’d suggest Dynamic Templates, but for simple HTML a legacy template will work.

Assign it a special name and save it. Click the white ‘Add Version’ button that appears. Finally, select ‘Code Editor’ from the options that appear.

You can write HTML directly in the editor that appears. As you edit, the canvas to the right automatically updates the preview. You can even toggle between views (desktop, mobile, and text) – pretty cool.

Insert the following HTML into the template body, overwriting the <%body%> tag there:

<p>Hello from Twilio and SendGrid!</p>
<img src="https://media.giphy.com/media/3oFzm06fG8g4FO0bMQ/giphy.gif" />

You should see something like this:

SendGrid HTML email template editor

At this point, hit ‘Save Template’.

Select the back arrow button, seen in the upper left hand corner of the above screenshot (left of ‘Code’). You’ll be taken back to the Legacy Transactional Templates page, where you can now see the new version with a random name.

Under your template name, you’ll see an ID. Copy that ID and keep it safe (perhaps in the same place you’ve got your API Key saved?):

SendGrid template ID used inside code

Note for later: Getting a blank body running the code? If you saved a version before the current version, you’ll have an active template expecting to pass through a body. It’s simple to fix: click the arrow to the left of ‘Show Inactive Versions’, then under the ‘ACTIONS’ header select ‘Make Active’ for the newest version.

Great work! Let’s move on to the code… we’re getting close now.

Write the SendGrid and Twilio Python

Create a new file twiliosendgrid.py in your project directory. This part’s simple - I’ve written the code you need already.

In that file paste the following, then save it:

"""Send an email and reply to an SMS with Twilio and SendGrid."""
from flask import Flask, request
import sendgrid
from sendgrid.helpers.mail import Email, Mail, Personalization
from validate_email import validate_email
import os

app = Flask(__name__)
sg = sendgrid.SendGridAPIClient(apikey=os.environ["SENDGRID_API_KEY"])


def send_email(to_email):
    """Send a templated email with SendGrid."""
    personalization = Personalization()
    personalization.add_to(Email(to_email))
    mail = Mail()
    mail.add_personalization(personalization)
    mail.from_email = Email("owl@example.com")
    mail.subject = "Ahoy from Twilio + SendGrid!"
    mail.template_id = os.environ["TEMPLATE_ID"]
    sg.client.mail.send.post(request_body=mail.get())


@app.route("/sms", methods=["GET", "POST"])
def incoming_sms():
    """Respond to an incoming SMS."""
    email = request.form.get('Body', None)

    if email is None or not validate_email(email):
        return (
            "<Response><Message>"
            "Please provide a valid email address."
            "</Message></Response>"
        )

    send_email(email)

    return "<Response><Message>Coding is fun!</Message></Response>"

if __name__ == "__main__":
    app.run(debug=False)

Here’s the above code’s flow:

  1. When we receive a message at the /sms endpoint, call the incoming_sms() function
  2. If the body of the SMS contains a valid email, call send_email()
  3. In send_email(), add the address as the to email address
  4. Add other metadata like the sender and subject
  5. Use the template we made above for the email
  6. Have SendGrid mail everything out
  7. Respond to Twilio’s /sms request with TwiML directing Twilio to reply

Seem like a good flow? We’ll soon see…

Set SendGrid Environment Variables

To prevent, well, API Keys on GitHub, it’s best to use environment variables in sensitive areas of your code. They’re also useful for constantly changing logic which relies on outside functionality.

Since you’ve been saving things fitting that classification in a safe place, let’s set some environment variables now for your Template ID and API Key from SendGrid. The following code will get it done in a terminal on Mac OSX:

export SENDGRID_API_KEY=<<SENDGRID_API_KEY>>
export TEMPLATE_ID=<<SENDGRID_TEMPLATE_ID>>

Replace <<SENDGRID_API_KEY>> and <<SENDGRID_TEMPLATE_ID>> with your Sendgrid API Key and Template ID called out in earlier steps.

Run ngrok and Set the Twilio Callback URL

When you run your app, usually your development server is only available locally. To expose it to the broader web you need to deploy it somewhere or mess with firewall settings.

There’s a third option. Open an ngrok “tunnel” to port 5000 (anticipating Flask later using that port):

ngrok http 5000

When you run ngrok, you’ll see a screen like the following:

ngrok curses screen upon opening port 5000

Now, open up the Twilio Incoming Numbers page in the console. Select the number you purchased.

Under ‘Messaging’ in the ‘A Message Comes In’ field, select ‘Webhook’. Paste in the ‘https’ forwarding email from the above ngrok screen followed by /sms:

ngrok URL in Twilio webhook

Hit the red ‘Save’ button.

We’re almost there!

Run and Test the Twilio SendGrid SMS Email Mashup

Ready to make some magic? Start Flask running:

FLASK_APP=twiliosendgrid.py flask run

Now you’re ready for the moment of truth...

From your cell phone, text the number you purchased with nothing but an email address in the body. If everything went right you should see two things in rapid succession:

  1. An SMS reply to your cell saying “Coding is fun!”
  2. An email in your inbox matching the template:

Example email from SMS and Email responder app in Python and Flask

Cheers to that. 🥂

Sameer and Jeff toast Twilio SendGrid Day One

Twilio and SendGrid: Day One

Awesome – now you have a Python app running with Twilio and SendGrid functionality! When you receive an SMS with an email address, you both reply to the SMS and email your clever message (and GIF, of course).

I had an awesome experience building this app, and I’m so thrilled to have earned my red Twilio track jacket. I personally hadn’t coded since 8th grade – and yet, with one week and a little help I was able to build something that felt magical.

Even before our companies came together today, we were kindred spirits. I’m so proud of what we’ve built with SendGrid and with Twilio. And to think: this is only Day One.

I can’t wait to see what we build together.

Sameer Dholakia is the CEO of Twilio SendGrid, a wholly owned subsidiary of Twilio. He's responsible for the overall strategy and operations of the Twilio SendGrid business unit. Outside Twilio, he’s at his happiest hanging out with his wife and kids, eating queso, and drinking margaritas.

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