Chapter 14: Email Slicer Program¶

🚀 Open Notebook¶

📺 Video Tutorial¶

Python email slicer program 📧 (4:07)

📚 What You’ll Learn¶

Extract username and domain from email addresses using string slicing - a practical application of string indexing!

🎯 Learning Objectives¶

Apply string indexing to extract specific parts of strings
Use the find() method to locate characters
Split email addresses into username and domain
Work with string slicing in real-world scenarios
Create interactive programs with user input

📖 Concept Explanation¶

Email Structure¶

An email address has two main parts separated by ‘@’:

Username: The part before ‘@’ (e.g., “john.doe”)
Domain: The part after ‘@’ (e.g., “example.com”)

Example: john.doe@example.com

Username: john.doe
Domain: example.com

Finding the @ Symbol¶

Use the find() method to locate the position of ‘@’:

email = "john.doe@example.com"
at_index = email.find("@")  # Returns 8

Extracting Username¶

Use slicing from the start to the @ position:

username = email[:at_index]  # Gets "john.doe"

Extracting Domain¶

Use slicing from after @ to the end:

domain = email[at_index + 1:]  # Gets "example.com"

💡 Examples¶

Basic Email Slicer¶

email = input("Enter your email: ")

# Find the @ symbol
at_index = email.find("@")

# Extract username and domain
username = email[:at_index]
domain = email[at_index + 1:]

print(f"Username: {username}")
print(f"Domain: {domain}")

Output:

Enter your email: alice@company.com
Username: alice
Domain: company.com

With Error Handling¶

email = input("Enter your email: ")

if "@" in email:
    at_index = email.find("@")
    username = email[:at_index]
    domain = email[at_index + 1:]
    
    print(f"Username: {username}")
    print(f"Domain: {domain}")
else:
    print("Invalid email format!")

Enhanced Version¶

email = input("Enter your email: ").strip()

if "@" in email and email.count("@") == 1:
    at_index = email.find("@")
    username = email[:at_index]
    domain = email[at_index + 1:]
    
    if username and domain:
        print(f"\n✅ Email Analysis:")
        print(f"   Username: {username}")
        print(f"   Domain: {domain}")
    else:
        print("❌ Invalid email format!")
else:
    print("❌ Email must contain exactly one @ symbol!")

✍️ Practice Exercises¶

Exercise 1: Basic Slicer¶

Create a program that:

Prompts user for an email
Extracts and displays username
Extracts and displays domain

Exercise 2: Domain Type Checker¶

Extend the program to identify the domain type:

.com → Commercial
.edu → Educational
.gov → Government
.org → Organization

email = input("Enter your email: ")
at_index = email.find("@")
domain = email[at_index + 1:]

if domain.endswith(".com"):
    print("Commercial domain")
elif domain.endswith(".edu"):
    print("Educational domain")
# Add more...

Exercise 3: Multiple Emails¶

Process multiple emails from a list:

emails = [
    "john@company.com",
    "alice@school.edu",
    "bob@government.gov"
]

for email in emails:
    at_index = email.find("@")
    username = email[:at_index]
    domain = email[at_index + 1:]
    print(f"{email} → User: {username}, Domain: {domain}")

🔍 Common Mistakes¶

1. Forgetting to Add 1¶

# ❌ Wrong - includes the @ symbol
domain = email[at_index:]

# ✅ Correct
domain = email[at_index + 1:]

2. Not Checking if @ Exists¶

# ❌ Wrong - crashes if no @
at_index = email.find("@")
username = email[:at_index]

# ✅ Correct
if "@" in email:
    at_index = email.find("@")
    username = email[:at_index]

3. Multiple @ Symbols¶

# Better to validate
if email.count("@") == 1:
    # Process email
else:
    print("Invalid email!")

🎮 Real-World Applications¶

Email Validation: Check if email format is correct
User Registration: Extract username for display
Email Sorting: Group emails by domain
Spam Detection: Analyze domain patterns
Contact Management: Organize contacts by email provider

🚀 Challenge Projects¶

Challenge 1: Email Statistics¶

Create a program that analyzes a list of emails and shows:

Most common domain
List of all unique domains
Number of emails per domain

Challenge 2: Email Formatter¶

Convert emails to different formats:

Original: john.doe@company.com
Display name: John Doe (john.doe@company.com)
Masked: j***e@company.com

Challenge 3: Professional Email Generator¶

Generate professional emails from names:

first_name = "John"
last_name = "Doe"
company = "techcorp"

# Generate: john.doe@techcorp.com
email = f"{first_name.lower()}.{last_name.lower()}@{company}.com"

📝 Key Takeaways¶

Email structure: username@domain
Use find() to locate the @ symbol
Slice before @ for username: email[:at_index]
Slice after @ for domain: email[at_index + 1:]
Always validate email format before processing
String slicing is powerful for text processing

🎓 Key Takeaways from Video¶

Variables store data values that can be reused
Test your code to ensure it works correctly
Follow along with the video for hands-on practice

💡 These points cover the main concepts from the video tutorial to help reinforce your learning.

🔗 Next Chapter¶

Continue to Chapter 15: Format Specifiers to learn advanced string formatting!

Practice Tip: Try extending this to validate email formats more thoroughly - check for valid characters, proper domain structure, etc!