RecursionError

RecursionError is raised when the maximum recursion depth is exceeded (default 1000). It's a subclass of RuntimeError and typically indicates infinite recursion or an algorithm that recurses too deeply.

Common causes

• Recursive function without a proper base case
• Circular references in __repr__ or __str__ methods
• __getattr__ that triggers itself recursively
• Recursive data structure traversal without cycle detection
• Algorithm that requires more depth than the limit allows

How to fix it

• Add or fix the base case in recursive functions
• Convert recursion to iteration using a stack or queue
• Increase limit with sys.setrecursionlimit() (use cautiously)
• Add visited tracking for graph/tree traversals
• Use functools.lru_cache to memoize and reduce recursion depth

Example

# Error example
def countdown(n):
    print(n)
    countdown(n - 1)  # No base case!

countdown(10)
# RecursionError: maximum recursion depth exceeded

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

# Fix: convert to iteration
def countdown(n):
    while n > 0:
        print(n)
        n -= 1

# Fix: memoization for expensive recursion
from functools import lru_cache

@lru_cache(maxsize=None)
def fibonacci(n):
    if n < 2:
        return n
    return fibonacci(n - 1) + fibonacci(n - 2)

Related errors