Question 51 markVery Short AnswerSection A

$What will be the output of the following statement ? `` python print("PythonProgram"[-1:2:-2]) ``$

Q: What will be the output of the following statement ? ```python print("PythonProgram"[-1:2:-2]) ```

**Output: `mroPo`** — obtained by slicing `"PythonProgram"` from index -1 down to (but not including) index 2, stepping backwards by 2 positions each time.

Q: How do I convert a negative index to a positive index in Python?

Add the string's length to the negative index. For a string of length 13, index -1 becomes $13 + (-1) = 12$.

Review of Python Basics (Class XI Recap)

String Slicing with Negative Step

Official answer

Output: mroPo — obtained by slicing "PythonProgram" from index -1 down to (but not including) index 2, stepping backwards by 2 positions each time.

string slicing

negative index

negative step

Python slice notation

index tracing

Marking scheme

1. $1 mark: for the correct output `mroPo` (character sequence and case exactly as traced from the original string).$

Hint

$Convert -1 to its positive index first (length + (-1)), then step backwards by 2 until you reach (but exclude) index 2.$

Quick oral answer

$Tracing indices 12,10,8,6,4 with a step of -2 from 'PythonProgram' gives the characters m,r,o,P,o, so the output is 'mroPo'.$

Common mistakes

1. $Forgetting to convert the negative start index -1 to its equivalent positive index before tracing.$
2. $Including the character at the stop index (index 2) — the stop value is always exclusive in slicing.$

Analysis and explanation

This is a classic negative-step string slicing question that tests careful index tracking. Concept The string "PythonProgram" has indices 0 to 12 (length 13): P(0) y(1) t(2) h(3) o(4) n(5) P(6) r(7) o(8) g(9) r(10) a(11) m(12). Slice [-1:2:-2] means: start at index -1 (i.e., index 12), stop before reaching index 2, step -2 (move backwards 2 positions each time). Index trace Start: index 12 \to 'm' Next: index 10 \to 'r' Next: index 8 \to 'o' Next: index 6 \to 'P' Next: index 4 \to 'o' Next would be index 2, but since stop=2 is exclusive, the slice stops here. Result Characters collected in order: m, r, o, P, o \to "mroPo" . Exam trap Students often forget that a negative start index converts to a positive index internally (start = length + start), and that the stop boundary is strictly exclusive.

Interesting facts

$Python slicing never raises an IndexError even if indices are out of range — it simply returns as many characters as fit within the valid range.$

$The general slicing formula s[start:stop:step] works identically for strings, lists, and tuples since they are all sequence types.$

Question details

Q5 of 48 questions

Board: CBSE
Class: Class 12
Subject: Computer Science
Year: 2026
Section: Section A
Marks: 1
Type: Very Short Answer
Chapter: Review of Python Basics (Class XI Recap)
Topic: $String Slicing with Negative Step$
Bloom's level: apply
Syllabus topic: $Unit 1: Computational Thinking and Programming - 2 — String Manipulation: Slicing with negative step$
Author: CBSE
Reviewed by: Padhantu Academic Team

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Frequently asked questions

$How do I convert a negative index to a positive index in Python?$

$13 + (-1) = 12$

$Is the stop index in Python slicing inclusive or exclusive?$

$The stop index is always exclusive — the character at the stop index is never included in the result, regardless of the direction of slicing.$