What is a Set in Python?

A set is a collection which is unordered, unindexed, and does not allow duplicate values. Sets are written with curly brackets {}.

Key Features of Sets:

• Unordered: No guaranteed order of elements.
• Unindexed: You cannot access items via index.
• No duplicate values.
• Mutable: You can add or remove items.

Creating a Set

# Creating a set
fruits = {"apple", "banana", "cherry"}
print(fruits)

Output:

{'banana', 'apple', 'cherry'}

Note: Order may vary.

Duplicate Values Are Ignored

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

Output:

{'banana', 'apple', 'cherry'}

Duplicate "apple" is automatically removed.

Check if Item Exists

fruits = {"apple", "banana", "cherry"}
print("banana" in fruits)

Output:

True

Add Items to a Set

fruits = {"apple", "banana"}
fruits.add("cherry")
print(fruits)

Output:

{'banana', 'apple', 'cherry'}

Add Multiple Items using update()

fruits = {"apple", "banana"}
fruits.update(["cherry", "mango"])
print(fruits)

Output:

{'banana', 'apple', 'cherry', 'mango'}

Remove Items from a Set

fruits = {"apple", "banana", "cherry"}
fruits.remove("banana")
print(fruits)

Output:

{'apple', 'cherry'}

If item not found, remove() raises an error. Use discard() to avoid this.

fruits.discard("orange")  # No error even if 'orange' is not present

Loop Through a Set

fruits = {"apple", "banana", "cherry"}
for fruit in fruits:
   print(fruit)

Output:

apple
banana
cherry

Order may vary.

Set Length

fruits = {"apple", "banana", "cherry"}
print(len(fruits))

Output:

3

Combine Two Sets using union()

a = {"apple", "banana"}
b = {"cherry", "banana"}
result = a.union(b)
print(result)

Output:

{'banana', 'apple', 'cherry'}

Keep Only Duplicates using intersection()

a = {"apple", "banana"}
b = {"banana", "cherry"}
result = a.intersection(b)
print(result)

Output:

{'banana'}

Keep All Except Duplicates using symmetric_difference()

a = {"apple", "banana"}
b = {"banana", "cherry"}
result = a.symmetric_difference(b)
print(result)

Output:

{'apple', 'cherry'}

Set Methods Summary

Set Exercises (Practice)

# Exercise: Remove duplicates from a list using set
my_list = [1, 2, 2, 3, 4, 4, 5]
unique = set(my_list)
print(unique)

Output:

{1, 2, 3, 4, 5}