Dictionaries and Sets

Learning Objectives: After this lesson, you'll master key-value pairs with dictionaries and unique collections with sets, understand when to use each data structure, and apply them to real-world problems.

Introduction to Dictionaries

A dictionary is Python's implementation of a hash table - a collection of key-value pairs where each key is unique. Think of it like a real dictionary where you look up a word (key) to find its definition (value).

Dictionary Operations

Dictionary Methods and Patterns

Working with Nested Dictionaries

Introduction to Sets

A set is an unordered collection of unique elements. Sets are perfect for:

• Removing duplicates
• Mathematical operations (union, intersection)
• Membership testing

Set Operations and Mathematics

Practical Applications

Example 1: Word Frequency Counter

Example 2: Student Grade Management

Practice Exercises

Exercise 1: Contact Book

Exercise 2: Inventory Management

Exercise 3: Text Analysis

Key Takeaways

✅ Dictionaries store key-value pairs with fast O(1) lookup time
✅ Dictionary methods - get(), keys(), values(), items(), update(), pop()
✅ Sets store unique elements and support mathematical operations
✅ Set operations - union (|), intersection (&), difference (-), symmetric difference (^)
✅ Choose dictionaries for mappings and fast lookups by key
✅ Choose sets for unique collections and mathematical operations
✅ Nested structures enable complex data organization
✅ Dictionary/set comprehensions provide concise creation syntax

Next Steps

In the next lesson, we'll explore advanced data structure operations - working with nested structures, combining different data types, and implementing common algorithms with our data structures.

Ready to master advanced data manipulation? The next lesson will show you powerful techniques for working with complex data!