Python Coding Challange - Question With Answer(01270325)

The given Python code has a recursive function named sum, but it will result in an infinite recursion error. Let's analyze why.

Understanding the Code:

python
def sum(num):
    return num + sum(num - 1) # Recursive call without a base case
print(sum(2))

Step-by-Step Execution:

1. print(sum(2)) calls sum(2).

2. Inside sum(2), it tries to return 2 + sum(1).

3. sum(1) then tries to return 1 + sum(0).

4. sum(0) tries to return 0 + sum(-1), and so on...

Since there is no base case (a condition to stop recursion), the function keeps calling itself indefinitely, causing a RecursionError: maximum recursion depth exceeded.

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Fixing the Code:

To make this function work correctly as a sum of natural numbers, we should add a base case:

def sum(num):
    if num <= 0: # Base case to stop recursion
       return 0
    return num + sum(num - 1)
print(sum(2)) # Output: 3 (2 + 1 + 0)

Correct Execution Flow:

sum(2) → 2 + sum(1) → 2 + (1 + sum(0)) → 2 + 1 + 0 = 3

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Key Takeaways:

• The original code lacks a base case, causing infinite recursion.

• Recursion needs a stopping condition (base case) to prevent infinite loops.

• The corrected function properly sums natural numbers recursively.

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