PCEP Control Flow, Loops, Lists and Logic Practice Question
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.
A program contains a nested while loop. The inner loop should run as long as a condition is True, but the outer loop should stop after 3 iterations. Which code structure is correct? (Assume the inner loop condition is inner < 5.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
outer = 0
while outer < 3:
inner = 0
while inner < 5:
# do something
inner += 1
outer += 1
Option D correctly implements a nested while loop where the inner loop runs while `inner < 5` and the outer loop runs while `outer < 3`. The inner loop increments `inner` to control its own termination, and the outer loop increments `outer` after the inner loop completes, ensuring exactly 3 iterations of the outer loop. This matches the requirement that the outer loop stops after 3 iterations while the inner loop runs as long as its condition is True.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
for outer in range(3):
inner = 0
while inner < 5:
# do something
inner += 1
Why it's wrong here
Uses for loop for outer, not while as required.
✗
outer = 0
while outer < 3:
for inner in range(5):
# do something
outer += 1
Why it's wrong here
Increments outer in inner loop; outer reaches 3 quickly.
✗
outer = 0
while outer < 3:
inner = 0
while inner < 5:
# do something
outer += 1
inner += 1
Why it's wrong here
Increments outer in inner loop; outer reaches 3 prematurely.
✓
outer = 0
while outer < 3:
inner = 0
while inner < 5:
# do something
inner += 1
outer += 1
Why this is correct
Correct; outer increments after inner loop completes.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Python Institute often tests the misconception that incrementing a loop counter inside a nested loop will correctly control both loops, when in fact it causes the outer loop to terminate prematurely, as seen in options B and C.
Detailed technical explanation
How to think about this question
In Python, nested loops require careful management of loop counters to avoid unintended early termination. The outer loop's counter (`outer`) must be incremented only after the inner loop completes, not inside the inner loop's body. This is a common pattern in algorithms like matrix traversal or grid-based simulations, where the outer loop controls rows and the inner loop controls columns. Misplacing the increment can lead to off-by-one errors or infinite loops if the condition never becomes False.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Control Flow, Loops, Lists and Logic — This question tests Control Flow, Loops, Lists and Logic — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: outer = 0
while outer < 3:
inner = 0
while inner < 5:
# do something
inner += 1
outer += 1 — Option D correctly implements a nested while loop where the inner loop runs while `inner < 5` and the outer loop runs while `outer < 3`. The inner loop increments `inner` to control its own termination, and the outer loop increments `outer` after the inner loop completes, ensuring exactly 3 iterations of the outer loop. This matches the requirement that the outer loop stops after 3 iterations while the inner loop runs as long as its condition is True.
What should I do if I get this PCEP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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