Quick Answer
The correct answer is `for i, val in enumerate(items): print(i, val)` because the built-in `enumerate()` function is specifically designed to iterate over list indices and values simultaneously, returning a tuple of (index, element) for each item in the sequence. This approach is both Pythonic and efficient, as it avoids the overhead of manually managing a counter with `range(len(items))` or the costly O(n) operation of calling `items.index(val)` inside the loop. On the Certified Entry-Level Python Programmer PCEP exam, this question tests your understanding of iteration patterns and the `enumerate()` function, a common topic in the "Control Flow" and "Data Collections" sections. A frequent trap is choosing `range(len(items))` and then using `items[i]` to access values, which works but is less readable and more error-prone. Remember the memory tip: "Enumerate gives you both the number and the member" — think of it as a built-in counter that saves you from writing extra code.
This PCEP practice question tests your understanding of computer programming and python fundamentals. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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 developer needs to iterate over the indices of a list named 'items' and print each index and its corresponding value. Which loop construct is most appropriate?
for val in items: print(items.index(val), val)
Why wrong: index() is inefficient and fails on duplicates.
for i in range(len(items)): print(i, items[i])
Why wrong: Works but not the most Pythonic.
for i, val in enumerate(items): print(i, val)
Pythonic and direct.
for i in items: print(i)
Why wrong: Only prints values, not indices.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
for i, val in enumerate(items): print(i, val)
Option C is correct because `enumerate(items)` returns an iterator that yields pairs of (index, value) directly, making it the most Pythonic and efficient way to iterate over both indices and values of a list. It avoids the overhead of calling `items.index(val)` (which is O(n) per iteration) or manually managing `range(len(items))`.
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.
for val in items: print(items.index(val), val)
Why it's wrong here
index() is inefficient and fails on duplicates.
for i in range(len(items)): print(i, items[i])
Why it's wrong here
Works but not the most Pythonic.
for i, val in enumerate(items): print(i, val)
Why this is correct
Pythonic and direct.
Related concept
Read the scenario before looking for a memorised answer.
for i in items: print(i)
Why it's wrong here
Only prints values, not indices.
Common exam traps
Python Institute often tests the distinction between iterating over values (`for val in items`) versus indices (`for i in range(len(items))`) versus both (`enumerate`), and the trap here is that candidates may choose Option B because it works, missing that `enumerate` is the idiomatic and recommended construct for this exact use case.
Detailed technical explanation
Under the hood, `enumerate()` creates an iterator that yields tuples `(index, value)` by calling `__next__` on the underlying iterable and maintaining an internal counter starting from 0 (or a custom start value). This is more memory-efficient than `range(len())` for large lists because it avoids constructing a separate range object and indexing each time. In real-world scenarios, `enumerate` is preferred in loops where both index and value are needed, such as when processing CSV rows or updating list items by position.
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
Computer Programming and Python Fundamentals — This question tests Computer Programming and Python Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: for i, val in enumerate(items): print(i, val) — Option C is correct because `enumerate(items)` returns an iterator that yields pairs of (index, value) directly, making it the most Pythonic and efficient way to iterate over both indices and values of a list. It avoids the overhead of calling `items.index(val)` (which is O(n) per iteration) or manually managing `range(len(items))`.
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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