Creating an appointment reminder app with Python SDK

Creating the application

Now we'll move on to the application itself.

The appointment_server.py file controls your app's business logic, allowing it to receive form data and send the appointment reminder by SMS. The full code sample is displayed on the right panel. Copy it and paste the contents into the appointment_server.py file in your project directory.

To get a good feel for how the code works, we'll walk through your application file one function at a time.

First lines of code

The appointment_server.py file begins with the following code:

Copy

Copied

from dotenv import load_dotenv
import os
from datetime import datetime, timedelta, timezone
from sinch import SinchClient
from flask import Flask, request, render_template, flash

load_dotenv()
app = Flask(__name__)
app.secret_key = "my_secret_key"


sinch_client = SinchClient(
    key_id=os.getenv("KEY_ID"),
    key_secret=os.getenv("KEY_SECRET"),
    project_id=os.getenv("PROJECT_ID")
)
sinch_client.configuration.sms_region = os.getenv("SMS_REGION")

This sets up your application by doing a few important things.

The environment variables are loaded into the application from the .env file.
A Flask application is created.
An SDK client object is initialized using the credentials in the .env file. This is something that will play a key role in your application.
Finally, the SMS region (eu or us) is set. You only really need to do this outside the United States as the client is initialized with a default region of us.

The `remind_patient` function

Now we'll review the remind_patient function, whose job is to send the SMS:

Copy

Copied

def remind_patient(to, message, reminder_datetime):
    send_batch_response = sinch_client.sms.batches.send(
        body=message,
        to=[to],
        from_=os.getenv("FROM_NUMBER"),
        delivery_report="none",
        send_at=reminder_datetime.strftime("%Y-%m-%dT%H:%M:%S")
        )
    print(send_batch_response)

This function is the keystone of your application. It does the work of sending the SMS by using the SinchClient instance you just created to call the SDK send method. What makes this method powerful is the send_at parameter. Because the Sinch SMS SDK has message scheduling built in, it's a one-stop shop for any application that requires sending SMS messages at particular times. This removes any need for your application to have auxillary task scheduling infrastucture. Moreover, it means you don't need your app to be running all the time!

In addition to send_at, the send method has a number of other parameters, including message expiry and delivery reports. These are described in more detail in the REST API reference.

The `appointment` function

Third let's review the appointment function:

Copy

Copied

def appointment():
    if request.method == "POST":
        appointment_date = datetime.strptime(
                    request.form['appointment_date'],
                    '%Y-%m-%d'
                    )
        appointment_time = datetime.strptime(
                    request.form['appointment_time'],
                    '%H:%M').time()
        appointment_datetime = datetime.combine(
            appointment_date,
            appointment_time
        )
        now = datetime.now()
        if appointment_datetime - timedelta(hours=2, minutes=5) < now:
            flash('Appointment must be at least 2:05 hours from now')
            return render_template('patient_details.html')
        reminder_datetime = appointment_datetime - timedelta(
                                                        hours=2,
                                                        minutes=5)
        message = ("Hi {patient}, you have a Sinch Hospital appointment with"
                   " Dr {doctor} scheduled for {appointment_time}".format(
                    patient=request.form['patient'],
                    doctor=request.form['doctor'],
                    appointment_time=str(appointment_datetime)
                    ))
        country_code = os.getenv('COUNTRY_CODE_US')
        if os.getenv('SMS_REGION') == "eu":
            country_code = os.getenv('COUNTRY_CODE_EU')
        to = country_code + request.form['phone']
        reminder_datetime = reminder_datetime.astimezone(timezone.utc)
        remind_patient(to, message, reminder_datetime)
        return render_template(
            'success.html',
            patient=request.form['patient'],
            doctor=request.form['doctor'],
            phone=request.form['phone'],
            appointment_datetime=str(appointment_datetime)
        )

    return render_template('patient_details.html')

This is your application's view. In Flask, a view is a function that accepts a request and performs an action. In this application, appointment receives form data from the front end and sends an SMS message by calling remind_patient. Once a message is sent, the user is redirected to the success.html page.

The function also contains validation to make sure any input appointment is scheduled at least two hours and five minutes into the future. This also stops users from accidently setting an appointment for a time in the past.

The Sinch SDK requires phone numbers to have a country code, so appointment checks the SMS region and adds a US/EU country code to the phone number.

Running the application

Finally, this is the code that runs your application:

Copy

Copied

if __name__ == '__main__':
    app.run(port=5010, debug=True)

Congratulations! That's the core of your application completed.

<<< Back Next >>>

Creating an appointment reminder app with Python SDK

Creating the application

First lines of code

The remind_patient function

The appointment function

Running the application

The `remind_patient` function

The `appointment` function