Calling a function before defining it

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 greeting, but throws a NameError. Fix the order.

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: NameError: name 'greet' is not defined. 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:

greet("Sam")

def greet(name):
    print(f"Hello, {name}!")

More functions problems

• Integer division and modulo easy
• Missing colon after function definition easy
• Comparison chains 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.