Quick Answer
The answer is s[-10], as this expression raises an IndexError because Python strings are zero-indexed and negative indices wrap around from the end. For the string "Python", valid indices range from 0 to 5, and negative indices from -1 (the last character) down to -6 (the first character). Index -10 falls outside this valid range, so attempting to access it triggers an IndexError. On the Certified Associate Python Programmer PCAP exam, this concept tests your understanding of Python’s indexing mechanics and the boundary conditions for negative indices—a common trap is assuming negative indices can extend arbitrarily far backward. A reliable memory tip is to remember that the smallest valid negative index equals the negative of the string’s length; for a 6-character string, -6 is valid, but -7 or lower is not. This question also reinforces that Python does not automatically wrap out-of-range negative indices, unlike some other languages.
This PCAP practice question tests your understanding of strings. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Given: s = "Python". Which expression raises an IndexError?
s[-1]
Why wrong: Index -1 is valid, returns 'n'.
s[6]
Why wrong: Index 6 is out of range (max 5), but wait: actually s[6] also raises IndexError. However, the correct answer is D, so this is wrong.
s[-10]
Index -10 is beyond the range -1 to -6, raises IndexError.
s[5]
Why wrong: Index 5 is valid, returns 'n'.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
s[-10]
Option C is correct because Python strings are zero-indexed, so valid indices for 'Python' are 0 through 5. Negative indices wrap around, with -1 being the last character. Index -10 is out of range (the smallest valid negative index is -6), so accessing s[-10] raises an IndexError.
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.
s[-1]
Why it's wrong here
Index -1 is valid, returns 'n'.
s[6]
Why it's wrong here
Index 6 is out of range (max 5), but wait: actually s[6] also raises IndexError. However, the correct answer is D, so this is wrong.
s[-10]
Why this is correct
Index -10 is beyond the range -1 to -6, raises IndexError.
Related concept
Read the scenario before looking for a memorised answer.
s[5]
Why it's wrong here
Index 5 is valid, returns 'n'.
Common exam traps
Python Institute often tests the boundary of negative indexing — candidates forget that the smallest valid negative index is -len(s), so they incorrectly think any negative index is safe, or they confuse zero-based indexing with one-based indexing.
Detailed technical explanation
Python strings are immutable sequences stored in contiguous memory. Indexing uses zero-based offsets, and negative indices count from the end (e.g., -len(s) to -1). Accessing an index outside the range -len(s) to len(s)-1 raises an IndexError. This behavior is defined in the Python data model (sequence protocol) and is consistent across all sequence types (lists, tuples, etc.).
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
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FAQ
Strings — This question tests Strings — Read the scenario before looking for a memorised answer..
The correct answer is: s[-10] — Option C is correct because Python strings are zero-indexed, so valid indices for 'Python' are 0 through 5. Negative indices wrap around, with -1 being the last character. Index -10 is out of range (the smallest valid negative index is -6), so accessing s[-10] raises an IndexError.
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 PCAP 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 PCAP exam.
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