Prove Strings Are Immutable

Easy ⏱ 8 min 87% acceptance ★★★★☆ 4.3

Strings in Python cannot be modified in place — s[0] = 'H' raises a TypeError. Write replace_char_at(s, index, new_char) that returns a new string with the character at index swapped for new_char, built entirely from slices (never mutating s).

Examples

Example 1

Input

s = 'hello', index = 0, new_char = 'H'

Output

'Hello'

Explanation

The character at index 0 is swapped; everything else is copied through.

Example 2

Input

s = 'cat', index = 2, new_char = 'r'

Output

'car'

Explanation

Works for any valid index, including the last one.

Constraints

0 <= index < len(s)
len(new_char) == 1

Topics

StringsImmutability

Companies

IBMOracle

Hints

Hint 1

Build the result as s[:index] + new_char + s[index+1:].

Hint 2

This never touches `s` itself — it constructs a brand-new string object.

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