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Using = instead of == in a condition

🐛 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 check if two numbers are equal, but won't even run. 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: SyntaxError: invalid syntax. 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:

a = 10
b = 10
if a = b:
    print("Equal")
else:
    print("Not equal")

Understand the rule

if x = 5: is a SyntaxError in Python because a single = is assignment and only == compares. Unlike C, Python refuses to let an assignment sit where a condition belongs, so this bug is caught before the program even starts — the interpreter points at the line during parsing. The exercise is to repair the condition and to understand why Python made this illegal.

How to trace it

A SyntaxError arrives before any code runs, so ignore program logic and look only at the flagged line.
Find the = inside the if/while/elif header and ask: is this meant to compare?
Replace = with == for equality; keep = only in ordinary assignment statements on their own line.
Modern Python (3.8+) prints a targeted hint: 'Maybe you meant == instead of ='.

Common wrong fixes

Deleting the whole condition or the variable to make the message go away instead of fixing the operator.
Confusing this with the walrus operator := — that one is legal in expressions but means something different.
Assuming the file crashed at runtime and adding try/except; syntax errors cannot be caught from within the same file.

Rule to remember

= assigns, == compares. Inside a condition, an = is a syntax error by design — Python would rather stop you at parse time than let an accidental assignment pass as truth.

Solve it in the interactive editor →

🐍 Learning path: Python Basics

Problem 6 of 12 in this path. Work them in order — each one builds on the rule before it.

← Missing colon after function definition Next in path: Next problem →

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.