If you use recursive function in your code for traversing a tree, computing factorial, or even parsing a nested data, you might have come across such an error in Python:

RecursionError: maximum recursion depth exceeded in comparison

Or sometimes:

RecursionError: maximum recursion depth exceeded while calling a Python object

Example:

def factorial(n): return n * factorial(n - 1)
print(factorial(5))

This works for small inputs, but try:

factorial(2000)

And it crashes with RecursionError.

Why This Happens

Python has a recursion limit to prevent infinite recursions and protect against stack overflows.

  • By default, Python allows only 1000 recursive calls (configurable).
  • If a recursive function doesn’t have a proper base case, or if the recursion goes too deep, Python raises a RecursionError.

This helps avoid system crashes due to unbounded memory usage.

Steps to Resolve the Issue RecursionError in Python

Step 1: Check Your Base Case

Every recursive function should have a clear and reachable base case.

Bad:

def countdown(n): print(n) return countdown(n - 1) # No base case → infinite recursion

Good:

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

Step 2: Use Iteration Instead of Recursion (if possible)

If recursion is not necessary, use a loop. Python is not optimized for deep recursion compared to functional languages.

Recursive:

def factorial(n): if n == 0: return 1 return n * factorial(n - 1)

Iterative:

def factorial(n): result = 1 for i in range(2, n+1): result *= i return result

Step 3: Increase the Recursion Limit (with caution)

If you genuinely need deep recursion (like for large tree parsing), increase the recursion limit using sys.setrecursionlimit():

import sys
sys.setrecursionlimit(3000)

Warning: Setting this too high can crash Python or your system if the stack overflows.

Step 4: Use Tail Recursion Optimization (Python doesn’t support it natively)

Unlike some languages (e.g., Scheme, Scala), Python does not optimize tail recursion, so deeply recursive tail calls still hit the recursion limit.

Alternative: Rewrite tail-recursive logic as loops or simulate with a stack.

Step 5: Use Stack-based Approach for Tree/Nested Data Processing

Instead of deep recursion, use an explicit stack:

def traverse(tree): stack = [tree] while stack: node = stack.pop() # Process node if node.children: stack.extend(node.children)

Conclusion

The RecursionError occurs when a function calls itself more times than Python allows, often due to a missing base case or large input. To avoid this, it’s best to hire Python developers who understand how to write safe and efficient recursive logic. Use clear stopping points, prefer loops for heavy tasks, and consider stack-based solutions for deeply nested data.