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Mixing text and numbers in print

🐛 Fix the bug Topic: strings Difficulty: easy Free

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

This should print an age message, but crashes. Fix it.

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 error it raises

Run the broken snippet and Python stops with this exact error: TypeError: can only concatenate str (not "int") to str. Match it to the Python errors guide, then repair the line that produced it — knowing the message is half the fix.

The snippet

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

age = 15
print("You are " + age + " years old")

Understand the rule

TypeError: can only concatenate str (not "int") to str is Python refusing to guess: 'Score: ' + 90 could mean 'Score: 90' or a math error, so the language raises instead of choosing. The + operator requires both sides to be strings or both to be numbers. This exercise repairs a print statement that glues text to an integer.

How to trace it

Identify each operand of the failing +: one side is a str, the other an int or float — the message states both types.
Decide the intent: text joining (convert the number) or arithmetic (convert the string).
For output, prefer an f-string: f'Score: {score}' converts automatically and stays readable.
Alternatively pass pieces as separate print arguments: print('Score:', score) inserts the space and does the conversion.

Common wrong fixes

Wrapping the whole expression in str(...), which hides which operand was the wrong type.
Using str() on the number but leaving the same bug on the next print three lines later — f-strings fix the pattern, not one line.
Believing print itself is the problem; the + fails before print ever runs.

Rule to remember

The + between a string and a number always raises TypeError. Build output with f-strings or multiple print arguments instead of manual concatenation and str() calls.

Solve it in the interactive editor →

🐍 Learning path: Python Basics

Problem 9 of 12 in this path. Work them in order — each one builds on the rule before it.

← Previous problem Next in path: String concatenation with + →

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.