List comprehension with condition in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of list comprehension filtering even numbers

What is the output of this Python code?

nums = [1, 2, 3, 4, 5]
even_nums = [x for x in nums if x % 2 == 0]
print(even_nums)

Python

nums = [1, 2, 3, 4, 5]
even_nums = [x for x in nums if x % 2 == 0]
print(even_nums)

A [2, 4]

B [1, 3, 5]

C [1, 2, 3, 4, 5]

D []

💡 Hint

Remember, the condition filters only numbers divisible by 2.

The list comprehension includes only numbers where x % 2 == 0, which are 2 and 4.

❓ Predict Output

intermediate

List comprehension with else clause output

What is the output of this code?

nums = [1, 2, 3]
result = [x if x % 2 == 0 else 0 for x in nums]
print(result)

Python

nums = [1, 2, 3]
result = [x if x % 2 == 0 else 0 for x in nums]
print(result)

A [0, 2, 0]

B [1, 2, 3]

C [1, 0, 3]

D [2]

💡 Hint

The else part replaces odd numbers with 0.

For each number, if it is even, keep it; otherwise, replace with 0. So 1 and 3 become 0, 2 stays 2.

❓ Predict Output

advanced

Output of nested list comprehension with condition

What does this code print?

matrix = [[1, 2], [3, 4], [5, 6]]
result = [x for row in matrix for x in row if x % 2 == 0]
print(result)

Python

matrix = [[1, 2], [3, 4], [5, 6]]
result = [x for row in matrix for x in row if x % 2 == 0]
print(result)

A [1, 2, 3, 4, 5, 6]

B [1, 3, 5]

C [2, 4, 6]

D [2, 4]

💡 Hint

It flattens the matrix and keeps only even numbers.

The comprehension goes through each row, then each number, and keeps only even numbers: 2, 4, 6.

❓ Predict Output

advanced

Output of list comprehension with multiple conditions

What is printed by this code?

nums = range(10)
result = [x*x for x in nums if x % 2 == 0 and x > 5]
print(result)

Python

nums = range(10)
result = [x*x for x in nums if x % 2 == 0 and x > 5]
print(result)

A [25, 36, 49, 64, 81]

B [0, 4, 16, 36, 64]

C [6, 8]

D [36, 64]

💡 Hint

Filter numbers that are even and greater than 5, then square them.

Only 6 and 8 are even and greater than 5. Their squares are 36 and 64.

🧠 Conceptual

expert

Understanding evaluation order in list comprehension with condition

Consider this code:

values = [0, 1, 2, 3]
result = [10 / x for x in values if x != 0]
print(result)

Which statement is true about this code?

A It raises a ZeroDivisionError because 0 is in values.

B It prints [10.0, 5.0, 3.3333333333333335] without error.

C It prints [10, 5, 3] because division returns integers.

D It raises a SyntaxError due to the condition placement.

💡 Hint

The condition filters out zero before division happens.

The condition x != 0 excludes zero, so division by zero never happens. Division returns floats.