Async email sending in Flask - Mini Project: Build & Apply

Async email sending

📖 Scenario: You are building a simple Flask web app that sends emails. To keep the app responsive, you want to send emails asynchronously, so the user does not wait for the email to be sent before getting a response.

🎯 Goal: Build a Flask app that sends an email asynchronously using a background thread.

📋 What You'll Learn

Create a Flask app with a route to send email

Set up a function to send email

Use a background thread to send email asynchronously

Return a response immediately after starting the email thread

💡 Why This Matters

🌍 Real World

Web applications often need to send emails like confirmations or notifications without making users wait. Sending emails asynchronously improves user experience by keeping the app responsive.

💼 Career

Understanding asynchronous tasks in web frameworks like Flask is essential for backend developers to build scalable and user-friendly applications.

1

Set up Flask app and email data

Create a Flask app instance called app and a dictionary called email_data with keys recipient, subject, and body having values '[e-mail]', 'Welcome', and 'Hello from Flask!' respectively.

Flask

from flask import Flask

# Create Flask app instance and email data
# Your code here

Need a hint?

Use Flask(__name__) to create the app. Define email_data as a dictionary with the exact keys and values.

2

Create a config variable for email sender

Add a variable called sender_email and set it to '[e-mail]' to represent the sender's email address.

Flask

from flask import Flask

app = Flask(__name__)

email_data = {
    'recipient': '[e-mail]',
    'subject': 'Welcome',
    'body': 'Hello from Flask!'
}

# Add sender_email variable
# Your code here

Need a hint?

Just create a variable sender_email and assign the exact string.

3

Define the async email sending function

Define a function called send_email that takes recipient, subject, and body as parameters. Inside, simulate sending email by importing time and calling time.sleep(2) to mimic delay. Then print f"Email sent to {recipient} with subject {subject}".

Flask

from flask import Flask

app = Flask(__name__)

email_data = {
    'recipient': '[e-mail]',
    'subject': 'Welcome',
    'body': 'Hello from Flask!'
}

sender_email = '[e-mail]'

# Define send_email function
# Your code here

Need a hint?

Use def send_email(recipient, subject, body):. Inside, import time and call time.sleep(2). Then print the message with f-string.

4

Create route to send email asynchronously

Import threading. Create a Flask route @app.route('/send') with a function send. Inside, start a new thread with target send_email and arguments email_data['recipient'], email_data['subject'], email_data['body']. Start the thread and return the string 'Email is being sent!' immediately.

Flask

from flask import Flask
import time

app = Flask(__name__)

email_data = {
    'recipient': '[e-mail]',
    'subject': 'Welcome',
    'body': 'Hello from Flask!'
}

sender_email = '[e-mail]'

def send_email(recipient, subject, body):
    time.sleep(2)
    print(f"Email sent to {recipient} with subject {subject}")

# Import threading and create /send route
# Your code here

Need a hint?

Import threading. Use @app.route('/send') and define send(). Create a thread with threading.Thread(target=send_email, args=(...)), start it, and return the message.