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Missing colon after function definition

🐛 Fix the bug Topic: functions Difficulty: easy Free

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

The challenge

This should print a square number, but won't even run. Fix the syntax.

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: SyntaxError: expected ':'. 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:

def square(n)
    return n * n

print(square(6))

Understand the rule

This PyDebug exercise focuses on missing colon after function definition. It is a small reproducible Python debugging task: identify the input and expected state, then predict each statement before changing code. When output differs, inspect types, boundaries, mutation, and control flow instead of guessing.

How to trace it

  1. Read the prompt and write the expected output for missing colon after function definition.
  2. Run the code mentally, recording values after each loop or function call.
  3. Compare actual and expected states and locate the first divergence.
  4. Make the smallest fix, then test a normal and a boundary case.

Common wrong fixes

Rule to remember

Treat missing colon after function definition as a focused experiment. A reliable solution explains the output, handles its edge case, and can be verified with a small test in the browser editor.

Solve it in the interactive editor →

🐍 Learning path: Python Basics

Problem 5 of 12 in this path. Work them in order — each one builds on the rule before it.

← Missing Colon in for LoopNext in path: Using = instead of == in a condition →

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