Question 505 of 498
PCEP Control Flow, Loops, Lists and Logic Practice Question
Which loop is more efficient for iterating over a large list when you only need the values, not indices?
⚠ Common exam trap
Python Institute often tests the misconception that `enumerate()` is always the best choice for iteration, but the trap here is that candidates overlook the specific requirement ('only the values, not indices') and choose a more general but less efficient option like B or A.
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 value in mylist:
Iterating directly over the list with `for value in mylist:` avoids the overhead of indexing or enumeration. This is the most efficient approach in Python for accessing only the values, as it uses the list's internal iterator, which is implemented in C and involves no function calls or index lookups per iteration.
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 i in range(len(mylist)): value = mylist[i]
Why it's wrong here
Requires index lookup each iteration.
- ✗
for i, value in enumerate(mylist):
Why it's wrong here
Includes index, slightly more overhead.
- ✓
for value in mylist:
Why this is correct
Direct iteration over values is most efficient.
- ✗
for value in mylist[::-1]:
Why it's wrong here
Reversed iteration is not needed and creates a copy.
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Last reviewed: Jun 30, 2026
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