Exam-style question
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Write a Python recursive function called countdown(n) that displays the values from n down to 1. State the base case and explain how the general case moves towards it.
Model answer
What a good answer should say
- ```python def countdown(n): if n == 0: return print(n) countdown(n - 1) ``` The base case is `n == 0`, which stops the function without making another call.
- The general case displays the current value and calls the function with `n - 1`, moving the argument towards zero.
Explanation
Why this works
A complete answer needs a stopping condition and a recursive call. The recursive call must change n so that repeated calls eventually reach the base case.
For example, countdown(3) displays 3, 2 and 1, then reaches countdown(0) and stops.
Common mistake
No common mistake is linked to this question yet.