Introduction to Sets

Sets are unordered collections of unique items in Python. They are useful when you need to store unique elements and perform set operations like union, intersection, and difference.

In this lesson, you’ll learn how to create and manipulate sets, and perform common set operations.

Creating Sets

A set is created by placing items inside curly braces {}, separated by commas. For example:

# Creating a set
fruits = {"apple", "banana", "cherry"}
print(fruits)

Unique Elements in Sets

Sets automatically remove duplicate items. For example:

# Sets with unique elements
numbers = {1, 2, 2, 3, 4, 4}
print(numbers)  # Outputs: {1, 2, 3, 4}

Set Operations: Union

The union() method returns a set containing all elements from two sets:

# Union of sets
set1 = {1, 2, 3}
set2 = {3, 4, 5}
print(set1.union(set2))  # Outputs: {1, 2, 3, 4, 5}

Set Operations: Intersection

The intersection() method returns a set containing only the elements that are common to both sets:

# Intersection of sets
set1 = {1, 2, 3}
set2 = {3, 4, 5}
print(set1.intersection(set2))  # Outputs: {3}

Set Operations: Difference

The difference() method returns a set containing elements in the first set but not in the second:

# Difference of sets
set1 = {1, 2, 3}
set2 = {3, 4, 5}
print(set1.difference(set2))  # Outputs: {1, 2}

Adding and Removing Elements

You can add or remove elements from a set using add() and remove() methods:

# Adding and removing elements
fruits = {"apple", "banana"}
fruits.add("cherry")
fruits.remove("banana")
print(fruits)  # Outputs: {'apple', 'cherry'}

Common Mistakes with Sets

Here are some mistakes to avoid:

• Trying to access set elements using an index (sets are unordered).
• Adding mutable objects like lists to a set (raises an error).
• Assuming sets maintain the order of elements.

What Did We Learn?

In this lesson, you learned:

• How to create and manipulate sets in Python.
• The uniqueness property of sets and common set operations.
• How to add and remove elements from sets.

Great job! Let’s move to the next topic.