Union and intersection in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this union operation?

Consider two sets A and B. What will be printed after the union operation?

Python

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

A {1, 2, 3}

B {3}

C {1, 2, 4, 5}

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

💡 Hint

Union combines all unique elements from both sets.

The union operator | returns a set with all unique elements from both sets. Here, elements 1, 2, 3, 4, and 5 appear in either A or B.

❓ Predict Output

intermediate

What is the output of this intersection operation?

Given two sets X and Y, what will be printed after the intersection operation?

Python

X = {10, 20, 30, 40}
Y = {30, 40, 50, 60}
print(X & Y)

A {30, 40}

B {10, 20}

C {50, 60}

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

💡 Hint

Intersection returns only elements common to both sets.

The intersection operator & returns a set with elements present in both sets. Here, 30 and 40 are common.

🧠 Conceptual

advanced

Which option shows the correct way to find the union of two sets using a method?

You want to find the union of sets set1 and set2 using a set method. Which option is correct?

A set1.intersection(set2)

B set1.add(set2)

C set1.union(set2)

D set1.update(set2)

💡 Hint

Union method returns a new set with all unique elements from both sets.

The union() method returns a new set with all elements from both sets. add() adds a single element, intersection() finds common elements, and update() modifies the set in place.

❓ Predict Output

advanced

What is the output of this combined union and intersection code?

Given sets a and b, what will be printed?

Python

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

A {3, 4}

B {1, 2, 3, 4}

C {5, 6}

D {1, 2}

💡 Hint

First union all elements, then intersect with set a.

The union a | b is {1, 2, 3, 4, 5, 6}. Intersecting with a keeps only elements in a, so result is {1, 2, 3, 4}.

🔧 Debug

expert

What error does this code raise?

Examine the code below. What error will it raise when run?

Python

set_a = {1, 2, 3}
set_b = [3, 4, 5]
result = set_a | set_b
print(result)

A TypeError

B SyntaxError

C NameError

D No error, prints {1, 2, 3, 4, 5}

💡 Hint

The union operator requires both operands to be sets.

The union operator | cannot be used between a set and a list. This causes a TypeError.