TypeError: string letters can't be reassigned

What this problem practises

Python strings are immutable sequences. "Fixing" a string always produces a new one, so the return value has to be captured; slicing rules apply, and every method — upper(), strip(), split(), join() — behaves differently from the in-place mutation you might be picturing.

This is a fix-the-bug problem: a short program is given in its broken state, and the task is to repair the code so it produces the required output. The interactive editor runs your fixed version in the browser and checks it for you — no setup, no local interpreter.

Difficulty: easy — the fix or the trick is normally a single line, and a careful read should be enough.

The challenge

Strings are immutable, so this program crashes with TypeError. Rebuild the string so it prints 'cee'.

The code runs in PyDebug’s in-browser compiler. Open the problem, run the snippet, watch the exact error or output, and keep iterating until it is right. Signed-in solves count toward XP and your daily streak.

The snippet

The interactive editor pre-fills exactly this code, broken and ready to repair:

s = 'bee'
s[0] = 'c'
print(s)

More strings problems

• f-string greeting easy
• TypeError: string letters can't be reassigned easy
• SyntaxError: unclosed parenthesis easy

Keep going

• Python debugging guide — a systematic method for finding bugs like this one fast.
• Browse every strings problem in this topic.
• Common Python errors and what they actually mean, plus the Python glossary for any term used on this page.