RecursionError: maximum recursion depth exceeded — how to fix

Traceback (most recent call last):
  File "app.py", line 2, in fact
    return n * fact(n - 1)
  [Previous line repeated 996 more times]
RecursionError: maximum recursion depth exceeded

Quick fix: Find the repeated line in the traceback and fix the base case so recursion stops. If the recursion is legitimately deep, rewrite it as a loop; sys.setrecursionlimit() is a last resort.

What it means

CPython limits the call stack to about 1000 frames (sys.getrecursionlimit()). Hitting it almost always means infinite recursion, not a problem that needs a bigger limit.

Cause 1: missing or unreachable base case

def fact(n):
    return n * fact(n - 1)      # never stops

def fact(n):
    if n <= 1:                  # base case
        return 1
    return n * fact(n - 1)

Also check that the argument actually moves toward the base case (e.g. fact(-1) or fact(2.5) with n == 1 as the check would never stop).

Cause 2: a property or setter that calls itself

class User:
    @property
    def name(self):
        return self.name        # calls the property again
    @name.setter
    def name(self, value):
        self.name = value       # calls the setter again

Store the value under a different attribute:

    @property
    def name(self):
        return self._name
    @name.setter
    def name(self, value):
        self._name = value

The same happens in __getattr__ / __setattr__ that access self.something directly; use object.__setattr__(self, ...) or self.__dict__.

Cause 3: a function shadowing a library name

def print(*args):
    print("LOG:", *args)        # calls itself

Rename your function.

Legitimately deep recursion

Deep tree walks or recursive algorithms on large inputs can exceed 1000 frames. Prefer an explicit stack:

def walk(root):
    stack = [root]
    while stack:
        node = stack.pop()
        visit(node)
        stack.extend(node.children)

If you really must, raise the limit (and know that too high a value can crash the interpreter with a segfault):

import sys
sys.setrecursionlimit(10_000)

Last updated 2026-10-27.