PCEP Computer Programming and Python Fundamentals Practice Question
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?
⚠ Common exam trap
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.
Answer choices
Why each option matters
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)
`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))`.
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 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.
- ✗
for i in items: print(i)
Why it's wrong here
Only prints values, not indices.
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