• Author: Amin Boulouma, Software Engineer
• Github source code: https://github.com/aminblm/ai_systems_design_from_scratch
• Engineering Blog: https://aminblm.github.io/ai_systems_design_from_scratch/blog/

The Infinite Loop: Debugging Python Initializers

Every software engineer, at least once in their career, makes the mistake of calling self.__init__() inside an __init__ method. The result? A RecursionError: maximum recursion depth exceeded. It’s a classic “funny bug”—simple to make, but a great lesson in how Python’s object model actually functions.

Glossary for the Young Engineer

• Initialization (__init__): The “setup” phase of a new object. Think of it like taking a brand new toy out of the box and putting the batteries in before you play.
• Recursion: When a function calls itself. Imagine standing between two mirrors and seeing an infinite tunnel of “you.”
• RecursionError: The computer’s way of saying “I have been doing the same thing over and over for too long, I am getting dizzy and I am going to stop now.”
• Infinite Loop: A circle that never ends, just like a song that keeps playing on repeat forever.

The Problem Space: The “Reset” Anti-Pattern

Engineers often attempt to use self.__init__() to “reset” an object’s state after it has already been created. This is fundamentally wrong because __init__ is intended to be called by the Python interpreter during object creation, not by the developer during the object’s lifecycle.

Why we never call __init__ manually: Manually calling it creates a circular dependency where the object never finishes being born because it is constantly trying to be born again.

Implementation

Simple Example: The Broken Initializer

This code will crash immediately upon instantiation.

class BrokenRobot:
    def __init__(self):
        # This calls itself infinitely!
        self.__init__() 

# robot = BrokenRobot() # Raises RecursionError

Complex Example: The Correct “Reset” Pattern

To manage state changes after initialization, use a separate, dedicated method. This separates the Creation Logic (which happens once) from the Reset Logic (which happens whenever you need).

class ResilientRobot:
    def __init__(self, name: str):
        self.name = name
        self.reset() # Proper: Calls a specific method, not the initializer

    def reset(self):
        """Dedicated method to restore state safely."""
        self.battery_level = 100
        self.tasks = []
        print(f"Robot {self.name} state reset.")

Quick Reference: Managing Object Lifecycle

Concept	Use Case	Why?
__init__	One-time setup	Called by Python at object birth.
reset()	State recovery	Called by the developer at any time.
Class Methods	Alternative constructors	Creates new objects with specific parameters.

Developer Checklist

• Method Names: Have I ensured no method calls its own parent initializer?
• State Separation: Have I separated “Creation” logic from “Cleanup” or “Reset” logic?
• Recursion Depth: If using actual recursion, have I implemented a clear exit condition (base case)?
• Testing: Did I write a unit test to ensure object instantiation completes without errors?

Final Takeaways

1. Never call __init__ twice. It is a reserved lifecycle hook for the Python interpreter.
2. Use dedicated methods. If you need to re-initialize an object, create a reset() or setup() method.
3. Respect the base case. If you must use recursion, always define a stopping point (a “base case”) to prevent infinite loops.