Day 23: Using Recursion Without a Base Case

 

🐍 Python Mistakes Everyone Makes ❌

Day 23: Using Recursion Without a Base Case

Recursion is powerful, but without a base case, it becomes dangerous. A recursive function must always know when to stop.

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❌ The Mistake

def countdown(n):
    print(n) 
    countdown(n - 1)

This function keeps calling itself endlessly.

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✅ The Correct Way

def countdown(n):
    if n == 0:    # base case
       return
     print(n) 
     countdown(n - 1)

Here, the base case (n == 0) tells Python when to stop making recursive calls.

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❌ Why This Fails

• No condition to stop recursion

• Function keeps calling itself forever

• Leads to RecursionError: maximum recursion depth exceeded

• Can crash your program

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🧠 Simple Rule to Remember

✔ Every recursive function must have a base case
✔ The base case defines when recursion ends
✔ No base case → infinite recursion

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🐍 Pro tip: Always ask yourself, “When does this recursion stop?”