Email verification pattern in Flask - Mini Project: Build & Apply

Email verification pattern

📖 Scenario: You are building a simple Flask web app where users can register with their email addresses. To ensure the email is valid, you want to implement an email verification pattern.This project guides you through setting up the data, configuration, core logic, and completion of the email verification feature.

🎯 Goal: Build a Flask app that accepts user email input, checks if the email format is valid using a regular expression, and displays a message indicating whether the email is valid or not.

📋 What You'll Learn

Create a Flask app with a route to accept email input

Use a regular expression to verify the email format

Display a success message if the email is valid

Display an error message if the email is invalid

💡 Why This Matters

🌍 Real World

Email verification is a common feature in web apps to ensure users provide valid contact information before accessing services.

💼 Career

Understanding how to implement email validation and user input handling in Flask is essential for backend web development roles.

1

DATA SETUP: Create a Flask app and import necessary modules

Write code to import Flask, request, and render_template from flask. Then create a Flask app instance called app.

Flask

from flask import Flask, request, render_template

# Create the Flask app instance
# Your code here

Need a hint?

Use app = Flask(__name__) to create the app instance.

2

CONFIGURATION: Define a regular expression pattern for email validation

Create a variable called email_pattern and assign it the regular expression string r"^[\w\.-]+@[\w\.-]+\.\w+$" to match valid email formats.

Flask

from flask import Flask, request, render_template

app = Flask(__name__)

# Define the email validation regex pattern
# Your code here

Need a hint?

The regex checks for characters before and after '@' and a domain suffix.

3

CORE LOGIC: Create a route to handle email input and validate it

Write a Flask route for '/' that accepts GET and POST methods. Inside the route function verify_email, get the email from request.form with key 'email'. Use the re module to check if the email matches email_pattern. Return render_template('result.html', message=message) where message is 'Valid email!' if it matches or 'Invalid email!' if not.

Flask

from flask import Flask, request, render_template
import re

app = Flask(__name__)

email_pattern = r"^[\w\.-]+@[\w\.-]+\.\w+$"

# Create route '/' with GET and POST methods
# Your code here

Need a hint?

Use @app.route decorator and request.form.get('email', '') to get the email.

4

COMPLETION: Add the HTML template to display the email input form and result message

Create a simple HTML form in a file named templates/result.html that shows an input field named email and a submit button. Below the form, display the message variable passed from Flask inside a paragraph tag.

Flask

from flask import Flask, request, render_template
import re

app = Flask(__name__)

email_pattern = r"^[\w\.-]+@[\w\.-]+\.\w+$"

@app.route('/', methods=['GET', 'POST'])
def verify_email():
    message = ''
    if request.method == 'POST':
        email = request.form.get('email', '')
        if re.match(email_pattern, email):
            message = 'Valid email!'
        else:
            message = 'Invalid email!'
    return render_template('result.html', message=message)

# Create templates/result.html with form and message display
# Your code here

Need a hint?

Use a form with method POST and display the message variable inside a paragraph.