Python Sets Tutorial – Create, Use, and Perform Set Operations with Examples

Table of Contents

1. What is Sets
2. Key Points about Sets
3. Creating Sets
4. Common Set Methods
5. Practical Examples
6. Tasks

1. What is Sets

In Python, a set is an unordered collection of unique elements, meaning no duplicates are allowed. Sets are useful when you want to store multiple items but don't need to keep them in a particular order, and you want to ensure that each item only appears once.

2. Key Points about Sets:

• Unordered: The elements in a set do not have a specific order.
• Unique: Sets automatically remove any duplicate items.
• Mutable: You can add or remove elements from a set.
• Immutable Elements: The items in a set must be immutable (e.g., numbers, strings, or tuples).

3. Creating Sets

# Create an empty set
empty_set = set()  # Note: {} creates an empty dictionary, not set!
 
# Create a set with elements
fruits = {'apple', 'banana', 'orange'}
numbers = {1, 2, 3, 4, 5}
 
# Convert list to set (removes duplicates)
colors = ['red', 'blue', 'green', 'blue', 'red']
unique_colors = set(colors)  # {'red', 'blue', 'green'}

Video Tutorial: How to Create Empty Set in Python

Another Example:

# Creating a set
fruits = {"apple", "banana", "cherry", "apple"}
 
# Displaying the set
print(fruits)  # Output: {'apple', 'banana', 'cherry'}

Notice how apple only appears once, even though we tried to add it twice.

4. Common Set Methods

1. Adding Elements

fruits = {'apple', 'banana'}
fruits.add('orange')  # Adds single element
fruits.update(['kiwi', 'mango'])  # Adds multiple elements
print(fruits)  # {'apple', 'banana', 'orange', 'kiwi', 'mango'}

Real-world use: Adding new unique tags to a blog post.

2. Removing Elements

numbers = {1, 2, 3, 4, 5}
numbers.remove(3)  # Raises error if element doesn't exist
numbers.discard(10)  # No error if element doesn't exist
popped = numbers.pop()  # Removes and returns arbitrary element
numbers.clear()  # Removes all elements

Video Tutorial: How to Add or Remove Elements in a Set

Real-world use: Removing items from a shopping cart while ensuring no duplicates.

3. Set Operations

Sets support mathematical operations like union, intersection, and difference.

• Union (|): Combines elements from both sets.
• Intersection (&): Finds common elements between sets.
• Difference (-): Finds elements in one set but not the other.

a = {1, 2, 3}
b = {3, 4, 5}
 
# Union (elements in either set)
print(a | b)  # {1, 2, 3, 4, 5}
 
# Intersection (elements in both sets)
print(a & b)  # {3}
 
# Difference (elements in a but not b)
print(a - b)  # {1, 2}
 
# Symmetric difference (elements in either set but not both)
print(a ^ b)  # {1, 2, 4, 5}

Video Tutorial: Find the Union of Two Sets in Python

Real-world use: Finding common friends between two users (intersection).

4. Membership Testing

vowels = {'a', 'e', 'i', 'o', 'u'}
print('a' in vowels)  # True
print('z' not in vowels)  # True

Real-world use: Checking if a username is in a blocked list.

5. Set Comparisons

set1 = {1, 2}
set2 = {1, 2, 3}
 
print(set1 <= set2)  # True (subset)
print(set2 >= set1)  # True (superset)
print(set1.isdisjoint({4, 5}))  # True (no common elements)

Real-world use: Checking if all required permissions are in a user's permission set.

5. Practical Examples

Example 1: Removing duplicates from a list

names = ['Alice', 'Bob', 'Alice', 'Charlie', 'Bob']
unique_names = list(set(names))
print(unique_names)  # Order not guaranteed: ['Alice', 'Bob', 'Charlie']

Example 2: Finding common interests between users

user1_interests = {'music', 'movies', 'sports'}
user2_interests = {'books', 'music', 'travel'}
 
common_interests = user1_interests & user2_interests
print(f"You both like: {common_interests}")  # {'music'}

Example 3: Validating survey responses

valid_answers = {'yes', 'no', 'maybe'}
responses = ['yes', 'no', 'sometimes', 'maybe', 'no']
 
invalid = set(responses) - valid_answers
print(f"Invalid responses: {invalid}")  # {'sometimes'}

When to Use Sets

• When you need to ensure elements are unique
• When you need fast membership testing (faster than lists)
• When mathematical set operations are needed
• When order doesn't matter

6. Tasks

Task 1: Creating a Set

Write a Python program that:

• Creates a set with four different numbers.
• Prints the set.

Example Output:

Numbers: {1, 2, 3, 4}

Task 2: Removing Duplicates Using a Set

Write a Python program that:

• Takes a list with duplicate numbers.
• Converts it into a set to remove duplicates.
• Prints the unique numbers.

Example Input:

Original List: [1, 2, 2, 3, 3, 4, 5]

Example Output:

Unique Numbers: {1, 2, 3, 4, 5}

Task 3: Creating and Using a Set

Write a Python program that:

• Creates a set of unique numbers from a given list (including duplicate values).
• Prints the unique numbers.

Example Input:

Original List: [1, 2, 2, 3, 4, 4, 5]

Expected Output:

Unique Numbers: {1, 2, 3, 4, 5}

Task 4: Set Operations

Write a Python program that:

• Creates two sets: one with even numbers and one with prime numbers (both from 1 to 10).
• Finds the union (all unique numbers from both sets).
• Finds the intersection (numbers that are in both sets).
• Prints the results.

Expected Output:

Even Numbers: {2, 4, 6, 8, 10}
Prime Numbers: {2, 3, 5, 7}
Union: {2, 3, 4, 5, 6, 7, 8, 10}
Intersection: {2}