UnboundLocalError: total used before assignment

What this problem practises

Function bugs are mostly about names and values: positional argument order, default parameters evaluated once at definition time, local versus global scope, and the implicit None returned whenever a function has no return.

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: medium — expect to hold two interacting rules in your head at once, such as a boundary combined with a mutation.

The challenge

This program crashes with UnboundLocalError because 'total' is assigned inside the function. Fix it so it prints 8.

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:

total = 0
def add_bonus(n):
    total = total + n
    return total
print(add_bonus(8))

More functions problems

• TypeError: missing function argument medium
• UnboundLocalError: total used before assignment medium
• SyntaxError: missing colon after if easy

Keep going

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