Python Basics — Dictionaries

Chapter 11 — Dictionaries

Dictionaries are Python’s most versatile data structure — they store data as key-value pairs and provide lightning-fast lookups O(1).

What You’ll Learn

Topic	Page
Creating Dictionaries	Creating Dictionaries →
Accessing & Modifying	Accessing & Modifying →
Dictionary Methods	Dictionary Methods →
Dictionary Comprehensions	Dictionary Comprehensions →
Nested Dictionaries	Nested Dictionaries →
Practice Exercises	Practice Exercises →

Quick Preview

# Creating a dictionary
user = {
    "name": "Alice",
    "age": 30,
    "email": "alice@example.com"
}

# Accessing values
print(user["name"])       # Alice
print(user.get("phone"))  # None (safe access)

# Adding a new key
user["phone"] = "555-1234"

# Iterating
for key, value in user.items():
    print(f"{key}: {value}")

Key Properties

Property	Description
Ordered	Insertion order preserved (Python 3.7+)
Mutable	Can add, modify, delete key-value pairs
Keys	Must be hashable (strings, numbers, tuples)
Values	Can be any type
Duplicates	Keys must be unique; values can repeat

---

Start Learning: Creating Dictionaries →