HTML email templates in Flask - Mini Project: Build & Apply

HTML Email Templates with Flask

📖 Scenario: You work at a small company that sends welcome emails to new users. You want to create a simple HTML email template using Flask to send personalized messages.

🎯 Goal: Build a Flask app that uses an HTML email template to send a welcome message with the user's name included.

📋 What You'll Learn

Create a Flask app with a route to send emails

Set up a dictionary with user data

Create an HTML email template with placeholders

Render the template with user data and prepare the email content

💡 Why This Matters

🌍 Real World

Companies often send personalized HTML emails to welcome new users or notify them about updates. Using Flask templates helps create dynamic email content easily.

💼 Career

Knowing how to build and render HTML email templates with Flask is useful for backend developers working on user communication and notification systems.

1

Set up user data dictionary

Create a dictionary called user with these exact entries: 'name': 'Alice' and 'email': '[e-mail]'.

Flask

# Your code here

Hint

Use curly braces to create the dictionary and include the keys 'name' and 'email' with the exact values.

2

Create Flask app and configure secret key

Import Flask from flask and create a Flask app instance called app. Then set app.secret_key to 'secret123'.

Flask

user = {'name': 'Alice', 'email': '[e-mail]'}
# Your code here

Hint

Remember to import Flask and create the app instance before setting the secret key.

3

Create HTML email template with placeholder

Create a string variable called email_template that contains this exact HTML: <h1>Welcome, {{ name }}!</h1><p>Thanks for joining us.</p>.

Flask

user = {'name': 'Alice', 'email': '[e-mail]'}
from flask import Flask
app = Flask(__name__)
app.secret_key = 'secret123'
# Your code here

Hint

Use double quotes for the string and include the exact HTML with the placeholder {{ name }}.

4

Render template with user data in Flask route

Import render_template_string from flask. Create a route @app.route('/send_email') with a function send_email() that returns render_template_string(email_template, name=user['name']).

Flask

user = {'name': 'Alice', 'email': '[e-mail]'}
from flask import Flask
app = Flask(__name__)
app.secret_key = 'secret123'
email_template = "Welcome, {{ name }}!Thanks for joining us."
# Your code here

Hint

Use the decorator @app.route('/send_email') and define the function send_email() that returns the rendered template string with the user's name.

Practice

1. What is the main purpose of using HTML email templates in Flask applications?

easy

A. To create visually appealing and structured email content

B. To speed up the sending of emails

C. To store email addresses securely

D. To encrypt email messages automatically

Solution

1. Step 1: Understand what HTML email templates do

   HTML email templates help format emails with colors, images, and layout to look professional.

2. Step 2: Identify the purpose in Flask context

   Flask uses templates to generate this HTML content dynamically for emails.

3. Final Answer:

   To create visually appealing and structured email content -> Option A

4. Quick Check:

   HTML email templates = visually appealing emails [OK]

Hint: HTML templates make emails look nice and professional [OK]

Common Mistakes:

• Confusing template purpose with email sending speed
• Thinking templates store email addresses
• Assuming templates encrypt emails

2. Which Flask function is commonly used to render an HTML email template from a file?

easy

A. render_template_string()

B. make_response()

C. send_email()

D. render_template()

Solution

1. Step 1: Recall Flask template rendering functions

   Flask provides render_template() to render templates from files and render_template_string() for strings.

2. Step 2: Identify the function for file templates

   For HTML email templates stored as files, render_template() is used.

3. Final Answer:

   render_template() -> Option D

4. Quick Check:

   File template rendering = render_template() [OK]

Hint: Use render_template() for file-based HTML templates [OK]

Common Mistakes:

• Using render_template_string() for file templates
• Confusing send_email() as a Flask function
• Using make_response() for rendering templates

3. Given this Flask code snippet for sending an email, what will be the content type of the email sent?

from flask_mail import Message
msg = Message(subject='Hello', recipients=['[e-mail]'])
msg.html = render_template('email.html', name='Alice')

medium

A. HTML formatted email

B. JSON formatted email

C. Multipart email with attachments

D. Plain text email

Solution

1. Step 1: Check how email content is set

   The code sets msg.html using render_template(), which produces HTML content.

2. Step 2: Understand Flask-Mail behavior

   Setting msg.html sends the email as HTML formatted content.

3. Final Answer:

   HTML formatted email -> Option A

4. Quick Check:

   msg.html set = HTML email [OK]

Hint: Setting msg.html sends HTML email content [OK]

Common Mistakes:

• Assuming plain text because no msg.body set
• Thinking attachments are included automatically
• Confusing JSON format with email content

4. Identify the error in this Flask email template rendering code:

msg = Message('Hi', recipients=['[e-mail]'])
msg.html = render_template('email_template.html')
send_email(msg)

medium

A. render_template() requires variables passed

B. msg.html should be msg.body

C. send_email() is not a Flask-Mail function

D. Message requires sender argument

Solution

1. Step 1: Check Flask-Mail sending function

   Flask-Mail uses mail.send(msg) to send emails, not send_email().

2. Step 2: Verify other parts

   Setting msg.html is correct for HTML content, and sender is optional if configured globally.

3. Final Answer:

   send_email() is not a Flask-Mail function -> Option C

4. Quick Check:

   Flask-Mail send = mail.send() [OK]

Hint: Use mail.send() to send emails, not send_email() [OK]

Common Mistakes:

• Using send_email() instead of mail.send()
• Confusing msg.html with msg.body
• Thinking sender is always required in Message

5. You want to send a personalized HTML email in Flask using a template that includes the user's name and a list of their favorite items. Which approach correctly combines rendering and sending the email?

hard

A. Use render_template_string() without variables, set msg.html, then mail.send(msg)

B. Render template with variables, set msg.html, then use mail.send(msg)

C. Set msg.body with template filename, then call mail.send(msg)

D. Set msg.html to plain text, then call mail.send(msg)

Solution

1. Step 1: Render template with variables

   Use render_template() passing user's name and list to generate HTML content.

2. Step 2: Assign rendered HTML to msg.html and send

   Set msg.html to the rendered content and send with mail.send(msg).

3. Final Answer:

   Render template with variables, set msg.html, then use mail.send(msg) -> Option B

4. Quick Check:

   Render with vars + msg.html + mail.send() = correct [OK]

Hint: Render with variables, assign to msg.html, send with mail.send() [OK]

Common Mistakes:

• Setting msg.body to template filename instead of content
• Not passing variables to render_template()
• Sending plain text in msg.html