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What are Sets in Ruby?

Ruby is a popular programming language known for its simplicity and elegance. If you are learning programming or just getting started with Ruby, you might have come across different data structures like arrays and hashes. In this blog post, we will explore another data structure called "sets" and understand how they can be useful in your Ruby programs.

What are Sets?

Think of a set as a collection of unique items, similar to an array. However, there is one key difference - sets do not allow duplicate values. This makes sets perfect for scenarios where you need to store and manipulate a group of distinct elements.

Sets are not native to Ruby, but they can be easily used by requiring the set module. Here's how to create a new set in Ruby:

require 'set'

my_set =

You can also initialize a set with some elements:

require 'set'

my_set =[1, 2, 3, 4])

Adding Elements to a Set

Adding elements to a set is quite straightforward. You can use the add or << methods to add elements to the set. Let's see how this is done:

require 'set'

my_set =
my_set << 2

puts my_set.inspect # Output: #<Set: {1, 2}>

It's important to note that if you try to add a duplicate element to the set, it will simply be ignored:

require 'set'

my_set =[1, 2, 3])

puts my_set.inspect # Output: #<Set: {1, 2, 3}>

Removing Elements from a Set

Removing elements from a set is as easy as adding them. You can use the delete method to remove an element from the set:

require 'set'

my_set =[1, 2, 3])

puts my_set.inspect # Output: #<Set: {1, 3}>

Iterating Over a Set

Sets can be iterated over using the each method, just like arrays and hashes:

require 'set'

my_set =[1, 2, 3, 4])

my_set.each do |element|
  puts "Current element: #{element}"

# Output:
# Current element: 1
# Current element: 2
# Current element: 3
# Current element: 4

Set Operations

One of the main reasons to use sets over other data structures is the ability to perform various set operations like union, intersection, and difference. Let's take a closer look at these operations.


Union of two sets is a new set that contains all the elements from both sets. In Ruby, you can use the | or union method to find the union of two sets:

require 'set'

set1 =[1, 2, 3])
set2 =[3, 4, 5])

union_set = set1 | set2
puts union_set.inspect # Output: #<Set: {1, 2, 3, 4, 5}>


Intersection of two sets is a new set that contains the elements common to both sets. In Ruby, you can use the & or intersection method to find the intersection of two sets:

require 'set'

set1 =[1, 2, 3])
set2 =[3, 4, 5])

intersection_set = set1 & set2
puts intersection_set.inspect # Output: #<Set: {3}>


Difference of two sets is a new set that contains the elements present in the first set but not in the second set. In Ruby, you can use the - or difference method to find the difference of two sets:

require 'set'

set1 =[1, 2, 3])
set2 =[3, 4, 5])

difference_set = set1 - set2
puts difference_set.inspect # Output: #<Set: {1, 2}>

When to Use Sets

Now that you have a good understanding of sets and their operations, you might wonder when to use them in your Ruby programs. Here are some scenarios where sets are useful:

  1. When you need a collection of unique elements without duplicates.
  2. When you want to perform operations like union, intersection, or difference on collections.
  3. When you need a faster lookup for elements as compared to arrays, since sets use hash tables for storage.


In this blog post, we explored sets in Ruby, how to create them, add and remove elements, iterate over them, and perform various set operations. Sets are a powerful data structure that can be quite useful in certain scenarios, and understanding how to use them can help you write cleaner and more efficient Ruby programs.

Remember to require 'set' when working with sets in Ruby, and keep in mind their unique characteristics, such as not allowing duplicate values and providing fast element lookups. Happy coding!