Contact Book0%
Quiz Application

Contact Book

Beginner15 min read•Updated: 2026-09-03
Study Materials

Contact Book

Build a persistent CLI Contact Book application that manages phone numbers, emails, and names.

Key Concepts & Detailed Explanation

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Code Examples & Output

Python
# Contact Book Application
class ContactBook:
def __init__(self):
self.contacts = {}
 
def add_contact(self, name, phone, email):
self.contacts[name.lower()] = {
"name": name,
"phone": phone,
"email": email
}
print(f"Contact '{name}' added successfully!")
 
def search_contact(self, name):
contact = self.contacts.get(name.lower())
if contact:
print(f"Name: {contact['name']} | Phone: {contact['phone']} | Email: {contact['email']}")
else:
print(f"No contact found for '{name}'.")
 
def list_all(self):
if not self.contacts:
print("Contact book is empty.")
return
print(f"\n--- Contact List ({len(self.contacts)}) ---")
for c in self.contacts.values():
print(f"• {c['name']} -> {c['phone']} ({c['email']})")
 
# Demonstration
book = ContactBook()
book.add_contact("Sumit Kumar", "+91 9876543210", "sumit@mskinstitute.in")
book.add_contact("Priya Sharma", "+91 9123456789", "priya@example.com")
book.search_contact("Sumit Kumar")
book.list_all()

Expected Output:

Output
Contact 'Sumit Kumar' added successfully!
Contact 'Priya Sharma' added successfully!
Name: Sumit Kumar | Phone: +91 9876543210 | Email: sumit@mskinstitute.in
 
--- Contact List (2) ---
• Sumit Kumar -> +91 9876543210 (sumit@mskinstitute.in)
• Priya Sharma -> +91 9123456789 (priya@example.com)

Best Practices & Common Pitfalls

Store dictionary keys in lowercase ('name.lower()') so user searches are case-insensitive.

Practice Quiz

1. Why should search keys be normalized to lowercase in contact book lookups?

  • A) Saves memory
  • B) Allows case-insensitive searching so 'Sumit' matches 'sumit'
  • C) Python requires lowercase dict keys
  • D) Prevents SQL injection
Answer: B Explanation: Normalizing keys enables case-insensitive lookups.

2. Which data structure provides the fastest average search time for contacts by name?

  • A) List
  • B) Dictionary (Hash Map)
  • C) Tuple
  • D) Array
Answer: B Explanation: Dictionaries provide O(1) average lookup time.

Practice Challenge

Add a 'delete_contact(name)' method and an 'export_to_csv(filename)' method to the Contact Book.

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