1 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.

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 slicingnegative indexnegative stepPython slice notationindex tracing

Marking Scheme

11 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'.

Analysis & 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 → 'm'
Next: index 10 → 'r'
Next: index 8 → 'o'
Next: index 6 → 'P'
Next: index 4 → '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 → "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.

Common Mistakes

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

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.

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Frequently Asked Questions

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 $13 + (-1) = 12$ .

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.