This PCEP practice question tests your understanding of control flow, loops, lists and logic. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
What is the output of the code?
numbers = [1, 2, 3, 4] result = [x**2 for x in numbers if x % 2 == 0]
print(result)
[2, 4]
Why wrong: These are the even numbers, not their squares.
[4, 16]
Correct squares of even numbers.
[1, 9]
Why wrong: Squares of odd numbers (1 and 3).
[2, 4, 16]
Why wrong: Includes incorrect item 2.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
[4, 16]
The list comprehension `[x**2 for x in numbers if x % 2 == 0]` iterates over `numbers`, filters for even numbers (2 and 4) using the condition `x % 2 == 0`, and squares each selected element. Squaring 2 gives 4, squaring 4 gives 16, so the result is `[4, 16]`. Option B is correct.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
[2, 4]
Why it's wrong here
These are the even numbers, not their squares.
[4, 16]
Why this is correct
Correct squares of even numbers.
Related concept
Read the scenario before looking for a memorised answer.
[1, 9]
Why it's wrong here
Squares of odd numbers (1 and 3).
[2, 4, 16]
Why it's wrong here
Includes incorrect item 2.
Common exam traps
Python Institute often tests the distinction between the filter condition and the transformation expression, so the trap here is that candidates may confuse the filtered elements with the transformed output, leading them to pick the original even numbers (option A) or a mix (option D).
Detailed technical explanation
List comprehensions in Python are syntactic sugar for a for-loop that builds a list; they execute the expression on the left for each element that passes the filter condition. The modulo operator `%` returns the remainder of division, so `x % 2 == 0` is True only for even integers. In real-world scenarios, such comprehensions are used for efficient data transformation, e.g., squaring only even sensor readings to avoid negative values.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the PCEP exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Control Flow, Loops, Lists and Logic — This question tests Control Flow, Loops, Lists and Logic — Read the scenario before looking for a memorised answer..
The correct answer is: [4, 16] — The list comprehension `[x**2 for x in numbers if x % 2 == 0]` iterates over `numbers`, filters for even numbers (2 and 4) using the condition `x % 2 == 0`, and squares each selected element. Squaring 2 gives 4, squaring 4 gives 16, so the result is `[4, 16]`. Option B is correct.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This PCEP practice question is part of Courseiva's free Python Institute certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCEP exam.
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