Fixing the Dreaded RecursionError: maximum recursion depth exceeded in Python

The RecursionError occurs in Python when a recursive function exceeds the maximum recursion depth, a limit set to prevent a stack overflow. I provide you insights into understanding and resolving this common error in recursive function implementations.

Understanding RecursionError

A recursion error typically indicates that your recursive function calls itself too many times, exceeding Python’s recursion depth limit. This limit is a safety feature to prevent infinite recursion leading to crashes or memory exhaustion.

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Strategies to Resolve RecursionError

Increasing the Recursion Limit

You can temporarily increase the recursion limit with sys.setrecursionlimit(), but do so with caution, as it can lead to crashes if the limit is too high:

import sys
sys.setrecursionlimit(1500) # Increase the recursion limit

Optimizing the Recursive Algorithm

Refactor your recursive function to reduce the number of recursive calls. Consider using iterative algorithms or optimizing with techniques like memoization.

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Using Tail Recursion

Where possible, rewrite recursive functions to use tail recursion, which can be more memory efficient. However, note that Python does not inherently optimize tail recursion.


Reduce redundant calculations by storing previously computed results of the recursive function:

def factorial(n, memo={}):
   if n in memo:
      return memo[n]
   if n <= 1:
      return 1
      memo[n] = n * factorial(n-1)
      return memo[n]

While encountering a RecursionError can be frustrating, it often signals opportunities for optimizing your code. By understanding the root causes and applying strategies like increasing the recursion limit cautiously, optimizing recursive algorithms, and employing memoization, you can effectively overcome this error, leading to more efficient and robust Python code.

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