Question 162 of 498
PCEP Control Flow, Loops, Lists and Logic Practice Question
A program reverses a string using a while loop. The code is:
text = "hello" reversed_text = "" index = len(text) - 1
while index > 0:
reversed_text += text[index] index -= 1
print(reversed_text)
It prints 'olle' instead of 'olleh'. What is the error?
⚠ Common exam trap
Python Institute often tests off-by-one errors in while loops, where candidates mistakenly think `index > 0` covers all elements because they forget that the first index is 0, not 1.
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
✓
Change the condition to 'while index >= 0:'
The while loop condition `index > 0` stops when `index` becomes 0, so the character at index 0 (the first character 'h') is never appended to `reversed_text`. Changing the condition to `while index >= 0:` ensures the loop runs for index values from 4 down to 0 inclusive, producing the full reversed string 'olleh'.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Change the condition to 'while index >= 0:'
Why this is correct
This ensures index 0 is processed.
- ✗
Change the initial index to len(text)
Why it's wrong here
That would cause an IndexError.
- ✗
Use a for loop instead
Why it's wrong here
Does not fix the specific bug.
- ✗
Use string slicing: reversed_text = text[::-1]
Why it's wrong here
A valid alternative but not the error in the code.
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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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