PCEP reversed() Practice Question
Which TWO of the following are valid ways to iterate over a list in reverse order? (Choose two.)
⚠ Common exam trap
A common trap is thinking that slicing with `[::-1]` is equivalent to `reversed()` for iteration. While both produce reverse order, slicing creates a new list, which may be memory-intensive and is not directly iterating over the original list. The exam often expects you to identify only the methods that iterate over the original list without creating a copy.
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 item in reversed(lst):
`reversed(lst)` returns an iterator that yields elements in reverse order without modifying the original list. Option B is correct because `range(len(lst)-1, -1, -1)` generates indices from the last to the first, allowing index-based access. These are the two valid methods according to the PCEP certification.
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 item in reversed(lst):
Why this is correct
Correct: `reversed(lst)` returns an iterator that yields elements in reverse order without copying the list.
- ✓
for i in range(len(lst)-1, -1, -1):
Why this is correct
Correct: `range(len(lst)-1, -1, -1)` produces indices from the last to the first, allowing access to elements in reverse order.
- ✗
for i in range(len(lst)):
Why it's wrong here
Incorrect: `range(len(lst))` generates indices 0 to len(lst)-1, which iterate forward, not reverse.
- ✗
for item in lst[-1::-1]:
Why it's wrong here
Incorrect: Slicing `lst[-1::-1]` creates a new reversed list, which is not iterating over the original list in place.
- ✗
for item in lst:
Why it's wrong here
Incorrect: Iterating over `lst` directly visits elements in their original forward order.
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