RecursionError in __repr__ or __str__

Why This Happens

When objects reference each other and their __repr__ methods print contents, calling repr() on either triggers infinite recursion. The same happens with __eq__ or any method traversing circular graphs.

The Problem

class Node:
    def __init__(self, value, parent=None):
        self.value = value
        self.parent = parent
    def __repr__(self):
        return f'Node({self.value}, parent={self.parent})'

The Fix

class Node:
    def __init__(self, value, parent=None):
        self.value = value
        self.parent = parent
    def __repr__(self):
        parent_val = self.parent.value if self.parent else None
        return f'Node({self.value}, parent_value={parent_val})'

Step-by-Step Fix

1. 1

   Identify the cycle

   Check for objects that reference each other.

2. 2

   Limit repr depth

   Only show identifiers, not full nested representations.

3. 3

   Use id() for references

   Show id(self.parent) instead of repr(self.parent).