Python Sets

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Python Sets Made Easy: A Complete Beginner-to-Pro Guide

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Python offers powerful built-in data types — and set is one of the most useful when working with unique values and set operations like union, intersection, and difference.

Let’s explore what sets are, how they work in Python, and where you can use them effectively.

What is a Set in Python?

A set is an unordered, unindexed collection of unique elements.
It’s great for removing duplicates, checking membership, and performing mathematical set operations.

my_set = {1, 2, 3, 4}
print(my_set)

✅ Output:

{1, 2, 3, 4}

Creating Sets in Python

1. Using Curly Braces

fruits = {"apple", "banana", "orange"}

2. Using the set() Constructor

numbers = set([1, 2, 3, 4])

❌ Duplicates Are Removed Automatically

data = {1, 2, 2, 3}
print(data)  # Output: {1, 2, 3}

Key Features of Sets

Feature Description
Unordered Items do not have a fixed index
Unique items No duplicate values
Mutable You can add or remove items
Iterable Can be looped through like lists

Basic Set Operations


Add Elements

my_set = {1, 2}
my_set.add(3)
print(my_set)  # {1, 2, 3}

Remove Elements

my_set.remove(2)  # Raises error if not found
my_set.discard(4)  # Safely ignores if not found

✅ Check Membership

if "apple" in fruits:
    print("Yes!")

🔄 Set Operations (Like Math Sets)

Let’s use two example sets:

A = {1, 2, 3, 4}
B = {3, 4, 5, 6}

Union (All elements)

print(A | B)  # {1, 2, 3, 4, 5, 6}

Intersection (Common elements)

print(A & B)  # {3, 4}

Difference (Items in A not in B)

print(A - B)  # {1, 2}

Symmetric Difference (Items not in both)

print(A ^ B)  # {1, 2, 5, 6}

When to Use Sets in Real Projects?

  • Remove duplicates from a list
  • Fast membership checks (in is faster in sets than lists)
  • 🔄 Compare collections of values
  • Data cleaning and deduplication

What You Cannot Do with Sets

  • ❌ Index or slice (e.g., my_set[0] will cause an error)
  • ❌ Store mutable items like lists inside a set (because they’re not hashable).

Set Vs List vs Tuple – Quick Comparison

Feature List Tuple Set
Ordered ✅ ✅ ❌
Mutable ✅ ❌ ✅
Duplicate Values ✅ ✅ ❌
Indexed ✅ ✅ ❌

Quick Example: Remove Duplicates from a List

items = [1, 2, 2, 3, 4, 4, 5]
unique_items = list(set(items))
print(unique_items)  # [1, 2, 3, 4, 5]

🧾 Conclusion

Python sets are a powerful tool for handling unique data, cleaning up collections, and doing fast comparisons. They're simple, but with many real-world uses in data science, web development, and automation.

If you know lists and dictionaries — learning sets gives you another handy tool in your Python toolkit.

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