All 15 Magic Methods & Operator Overloading questions
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What is the difference between __str__ and __repr__? How does __repr__ help with debugging when printing a list of custom objects? How do you overload arithmetic operators like + and - using __add__ and __sub__? What do __eq__ and __hash__ need to satisfy together, and what happens if you only override __eq__? How do __len__, __getitem__, and __setitem__ let a custom class act like a sequence or mapping? How does __call__ let an instance of a class be invoked like a function? How do comparison magic methods like __lt__, __le__, __gt__, and __ge__ support custom sorting? How does __contains__ let you customize the behavior of the 'in' operator? How do you implement custom attribute access with __getattr__ versus __getattribute__? How do context manager magic methods __enter__ and __exit__ work, and what does __exit__'s return value control?
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What are 'magic methods' (dunder methods) in Python, and why are they called that?

Beginner

Answer

Magic methods are special methods surrounded by double underscores (e.g., __init__, __str__, __add__) that Python calls implicitly in response to built-in operations like construction, printing, arithmetic, or comparisons. They're called 'dunder' methods (double underscore) and let custom classes integrate with Python's built-in syntax and functions.
class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y
    def __repr__(self):
        return f'Point({self.x}, {self.y})'

p = Point(1, 2)
print(p)  # Point(1, 2) -- uses __repr__
Real-world example A custom Money class defines __add__, __eq__, and __repr__ so instances can be added and compared with natural + and == syntax instead of explicit method calls.

Common follow-ups: What's the difference between __str__ and __repr__?;Which dunder methods does len() rely on?

Data Types & Structures;Dataclasses & NamedTuples
All 15 Magic Methods & Operator Overloading questions