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Creating Set

  • This lesson explains how to create sets in Python and store unique values.

  • A set in Python is a built-in data type used to store multiple unique values in a single variable.

    • Sets do not allow duplicate values

    • Sets are unordered (no fixed position)

    • Sets are mutable (you can add or remove items)

    • Written using curly braces {}


    Daily Life Example

    Think of a set like:

    • A collection of unique roll numbers in a class

    • Unique visitors on a website

    • Unique items in a shopping cart

    If the same value appears twice, Python keeps only one copy.


Create a Set using Curly Braces {}

Basic Set Creation 

fruits = {"apple", "banana", "mango"}
print(fruits)

  • Code Description:

    • A set named fruits is created.

    • Items are stored inside { }.

    • Order may change in output (sets are unordered).

Duplicate Values Are Removed Automatically

Set Removes Duplicates 

numbers = {1, 2, 3, 2, 1}
print(numbers)

  • Code Description

    • Even though 1 and 2 appear twice, set keeps only unique values.

    • Output will contain only {1, 2, 3}.

Using set() Constructor

Used when converting other data types to a set. 

letters = set(["a", "b", "c", "a"])
print(letters)

  • Code Description

    • A list is converted into a set.

    • Duplicate "a" is removed.

  • Creating an Empty Set

    {} creates an empty dictionary, not a set.

Correct Way to Create Empty Set 

empty_set = set()
print(type(empty_set))

Creating Set with Mixed Data Types

Set with Different Data Types 

data = {10, "Python", True, 3.14}
print(data)

  • Important Rules of Sets

    • Elements must be immutable (no list or dictionary inside set)

    • No duplicate values allowed

    • Sets are faster for membership checking

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