Subset and superset checks in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this subset check?

Consider the following Python code:

set_a = {1, 2, 3, 4}
set_b = {2, 3}

What is the output of set_b.issubset(set_a)?

Python

set_a = {1, 2, 3, 4}
set_b = {2, 3}
print(set_b.issubset(set_a))

A True

B False

C TypeError

D None

💡 Hint

Remember, a subset means all elements of one set are in the other.

set_b contains elements 2 and 3, both of which are in set_a. So set_b is a subset of set_a, and the method returns True.

❓ Predict Output

intermediate

What does this superset check return?

Look at this code:

set_x = {5, 6, 7, 8}
set_y = {6, 7}

What is the output of set_x.issuperset(set_y)?

Python

set_x = {5, 6, 7, 8}
set_y = {6, 7}
print(set_x.issuperset(set_y))

A True

B KeyError

C False

D None

💡 Hint

Superset means the first set contains all elements of the second.

set_x contains 5,6,7,8 which includes all elements of set_y (6,7), so it returns True.

❓ Predict Output

advanced

What is the output of this subset check with an empty set?

Given:

set_m = set()
set_n = {1, 2, 3}

What does set_m.issubset(set_n) print?

Python

set_m = set()
set_n = {1, 2, 3}
print(set_m.issubset(set_n))

A False

B True

C TypeError

D None

💡 Hint

Think about whether an empty set is a subset of any set.

An empty set is considered a subset of every set, so the method returns True.

❓ Predict Output

advanced

What does this superset check return?

Look at this code:

set_a = {1, 2, 3}
not_a_set = [1, 2]

What happens when running set_a.issuperset(not_a_set)?

Python

set_a = {1, 2, 3}
not_a_set = [1, 2]
print(set_a.issuperset(not_a_set))

A AttributeError

B False

C True

D TypeError

💡 Hint

issuperset accepts any iterable, not just sets.

issuperset accepts any iterable argument, so it checks if all elements of the list are in the set. Since 1 and 2 are in set_a, it returns True.

🧠 Conceptual

expert

Which option shows the correct way to check if set A is a strict subset of set B?

You want to check if set A is a subset of set B but not equal to B. Which code snippet does this correctly?

A set_a.issuperset(set_b)

B set_a <= set_b

C set_a.issubset(set_b) and set_a != set_b

D set_a < set_b

💡 Hint

Python has operators for strict subset and subset or equal.

The < operator checks for strict subset (subset but not equal). The <= operator allows equality. Option D is logically correct but less concise. Option D checks superset, which is the opposite.

Practice

1. Which of the following statements correctly describes a subset in Python sets?

easy

A. All elements of set A are in set B.

B. Set A has more elements than set B.

C. Set A and set B have no common elements.

D. Set A and set B have exactly the same elements.

Solution

1. Step 1: Understand subset definition

   A set A is a subset of set B if every element in A is also in B.

2. Step 2: Match definition to options

   All elements of set A are in set B. states all elements of A are in B, which matches the subset definition.

3. Final Answer:

   All elements of set A are in set B. -> Option A

4. Quick Check:

   Subset means all elements inside another set [OK]

Hint: Subset means every item of one set is inside another [OK]

Common Mistakes:

• Confusing subset with superset
• Thinking subsets must have fewer elements
• Assuming no common elements means subset

2. Which of the following is the correct syntax to check if set A is a superset of set B in Python?

easy

A. A.issubset(B)

B. A <= B

C. A.issuperset(B)

D. A < B

Solution

1. Step 1: Recall superset method

   To check if A is a superset of B, use A.issuperset(B) or A >= B.

2. Step 2: Identify correct option

   A.issuperset(B) uses A.issuperset(B), which is the correct method.

3. Final Answer:

   A.issuperset(B) -> Option C

4. Quick Check:

   Superset check uses issuperset() method [OK]

Hint: Use issuperset() to check if A contains all of B [OK]

Common Mistakes:

• Using issubset() instead of issuperset()
• Using <= or < for superset checks
• Confusing method names

3. What will be the output of the following code?

set_a = {1, 2, 3}
set_b = {1, 2, 3, 4, 5}
print(set_a <= set_b)
print(set_b >= set_a)

medium

A. False\nFalse

B. False\nTrue

C. True\nFalse

D. True\nTrue

Solution

1. Step 1: Evaluate set_a <= set_b

   set_a has elements {1,2,3}, all of which are in set_b, so set_a is subset of set_b, result is True.

2. Step 2: Evaluate set_b >= set_a

   set_b contains all elements of set_a, so set_b is superset of set_a, result is True.

3. Final Answer:

   True True -> Option D

4. Quick Check:

   Subset and superset checks both True [OK]

Hint: <= and >= check subset and superset respectively [OK]

Common Mistakes:

• Mixing up <= and >= operators
• Assuming strict subset/superset without equality
• Forgetting sets can be equal

4. The following code is intended to check if set A is a subset of set B, but it raises an error. What is the problem?

set_a = {1, 2}
set_b = {1, 2, 3}
result = set_a.subset(set_b)
print(result)

medium

A. Sets cannot be compared using methods.

B. The method name should be issubset(), not subset().

C. The sets must be converted to lists first.

D. The print statement is missing parentheses.

Solution

1. Step 1: Identify method name error

   The correct method to check subset is issubset(), not subset().

2. Step 2: Confirm correct usage

   Using set_a.issubset(set_b) returns True or False without error.

3. Final Answer:

   The method name should be issubset(), not subset(). -> Option B

4. Quick Check:

   issubset() is correct method name [OK]

Hint: Use issubset(), not subset(), to check subsets [OK]

Common Mistakes:

• Using wrong method names
• Thinking sets need conversion to lists
• Confusing print syntax errors

5. Given two sets:

set_x = {2, 4, 6, 8}
set_y = {4, 6}

Which of the following expressions will return True for checking if set_y is a proper subset of set_x (subset but not equal)?

hard

A. set_y < set_x

B. set_y >= set_x

C. set_x.issubset(set_y)

D. set_y.issuperset(set_x)

Solution

1. Step 1: Understand proper subset

   A proper subset means all elements of set_y are in set_x, and sets are not equal.

2. Step 2: Analyze options

   set_y < set_x uses < operator which checks proper subset (subset but not equal). set_y >= set_x checks superset (wrong direction). set_x.issubset(set_y) reverses the sets (wrong). set_y.issuperset(set_x) is wrong (issuperset).

3. Final Answer:

   set_y < set_x -> Option A

4. Quick Check:

   Proper subset uses < operator [OK]

Hint: Use < for proper subset (subset but not equal) [OK]

Common Mistakes:

• Using >= which checks superset
• Reversing the subset direction
• Confusing issubset() with issuperset()