Why sets are used in Python - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of set operations

What is the output of this Python code using sets?

Python

a = {1, 2, 3, 4}
b = {3, 4, 5, 6}
print(a & b)

A {1, 2}

B {5, 6}

C {3, 4}

D {1, 2, 3, 4, 5, 6}

💡 Hint

The & operator finds common elements in both sets.

The & operator returns the intersection of two sets, which are elements present in both. Here, 3 and 4 are common.

❓ Predict Output

intermediate

Why sets remove duplicates

What will be the output of this code?

Python

numbers = [1, 2, 2, 3, 4, 4, 4, 5]
unique = set(numbers)
print(len(unique))

A 5

B 8

C 4

D 7

💡 Hint

Sets only keep unique items, no repeats.

The list has duplicates but the set keeps only unique values: 1,2,3,4,5, so length is 5.

❓ Predict Output

advanced

Set difference operation output

What does this code print?

Python

x = {10, 20, 30, 40}
y = {30, 40, 50, 60}
print(x - y)

A {10, 20}

B {30, 40}

C {50, 60}

D {10, 20, 30, 40, 50, 60}

💡 Hint

The - operator removes elements of y from x.

x - y returns elements in x that are not in y, which are 10 and 20.

❓ Predict Output

advanced

Using sets to check membership efficiently

What is the output of this code?

Python

items = ['apple', 'banana', 'cherry']
item_set = set(items)
print('banana' in item_set)
print('orange' in item_set)

A True\nTrue

B True\nFalse

C False\nTrue

D False\nFalse

💡 Hint

Sets allow fast membership checks.

'banana' is in the set so True, 'orange' is not so False.

🧠 Conceptual

expert

Why use sets instead of lists for membership tests?

Which is the main reason sets are preferred over lists for checking if an item exists?

A Lists can only store numbers, sets can store any type.

B Sets keep elements in order, lists do not.

C Lists use less memory than sets.

D Sets allow faster membership tests than lists.

💡 Hint

Think about speed when checking if something is inside.

Sets use a special method to check membership quickly, usually faster than lists which check one by one.