Factorial of 3

What this problem practises

Recursion needs a base case that actually triggers. A missing or drifting base case ends in RecursionError, and the call-stack order decides which value comes back first when predictions are made by eye.

This is an output-prediction problem: read the snippet carefully and write down exactly what it prints before anything runs. These questions are interview staples because they test whether you know the language rules, or merely recognise their syntax.

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

The challenge

What will this program print? Type the exact output.

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 — read it, then submit your prediction:

def fact(n):
    if n <= 1:
        return 1
    return n * fact(n - 1)
print(fact(3))

More recursion problems

• RecursionError: counting the wrong way hard
• Factorial of 4 medium
• Factorial of 7 medium

Keep going

• Output-prediction strategies — how to predict tricky snippets without running them.
• Browse every recursion problem in this topic.
• Common Python errors and what they actually mean, plus the Python glossary for any term used on this page.