What is a set in Python and how to use it?

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Jayant Kumar · Accepted Answer

Table of Contents
Introduction:
In Python, a set is a built-in data structure that represents an unordered collection of unique elements. Sets are useful for performing operations like union, intersection, and difference, and they are ideal for removing duplicates and testing membership.
Key Characteristics of Sets

Unordered: Sets do not maintain the order of elements.
Unique Elements: Sets automatically ensure that all elements are unique, meaning no duplicates are allowed.
Mutable: Sets are mutable, so you can add or remove elements after creation.
No Indexing: Elements in a set are not accessed by index.

Basic Syntax:
my_set = {1, 2, 3, 4}

You can also create an empty set using the set() constructor:
empty_set = set()

Common Operations with Sets

Adding Elements

Use the add() method to add an element to a set:
my_set = {1, 2, 3}
my_set.add(4)
print(my_set)  # Output: {1, 2, 3, 4}

Removing Elements

Use the remove() method to remove a specific element. Note that if the element is not found, remove() raises a KeyError. To avoid this, use discard() which removes the element if it exists but does nothing if it does not.
my_set = {1, 2, 3, 4}
my_set.remove(2)
print(my_set)  # Output: {1, 3, 4}

my_set.discard(5)  # No error even though 5 is not in the set

Checking Membership

Use the in keyword to check if an element exists in a set:
my_set = {1, 2, 3}
print(2 in my_set)  # Output: True
print(4 in my_set)  # Output: False

Set Operations

Union: Combine elements from two sets.
set1 = {1, 2, 3}
set2 = {3, 4, 5}
union_set = set1 | set2
print(union_set)  # Output: {1, 2, 3, 4, 5}

Intersection: Get common elements from two sets.
intersection_set = set1 &#x26; set2
print(intersection_set)  # Output: {3}

Difference: Get elements in one set that are not in another.
difference_set = set1 - set2
print(difference_set)  # Output: {1, 2}

Symmetric Difference: Get elements in either of the sets but not in both.
symmetric_difference_set = set1 ^ set2
print(symmetric_difference_set)  # Output: {1, 2, 4, 5}

Copying Sets

Use the copy() method to create a shallow copy of a set:
original_set = {1, 2, 3}
copied_set = original_set.copy()
print(copied_set)  # Output: {1, 2, 3}

Practical Use Cases

Removing Duplicates: Convert a list to a set to automatically remove duplicates.
numbers = [1, 2, 2, 3, 4, 4, 5]
unique_numbers = set(numbers)
print(unique_numbers)  # Output: {1, 2, 3, 4, 5}

Membership Testing: Use sets for fast membership testing in large collections.

Mathematical Operations: Leverage set operations for tasks involving intersections, unions, and differences.

Conclusion:
Sets in Python offer a powerful and efficient way to handle collections of unique items. Their support for mathematical set operations and their ability to automatically remove duplicates make them versatile tools for various programming tasks. Understanding how to use sets effectively can help you manage data more efficiently and perform complex operations with ease.

What is a set in Python and how to use it?

Table of Contents

Introduction:

Conclusion:

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