What are dunder (magic) methods?

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**Dunder** ('double underscore') methods like `__init__`, `__repr__`, `__len__`, `__eq__`, `__iter__`, `__add__` are hooks Python's syntax and built-ins call on your behalf. By implementing them, your objects integrate naturally with the language — this is how Python does **operator overloading** and the **data model / protocols**.

Some you'll define most:

- `__init__` — initialize a new instance; `__new__` actually creates it.
- `__repr__` / `__str__` — debug vs user-facing string. Always provide `__repr__`.
- `__eq__` (+ `__hash__`) — value equality and hashability.
- `__len__`, `__getitem__`, `__iter__`, `__contains__` — make an object behave like a container/sequence.
- `__add__`, `__lt__`, `__call__`, `__enter__`/`__exit__` — operators, callables, context managers.

`len(x)` calls `x.__len__()`, `x + y` calls `x.__add__(y)`, `for i in x` calls `x.__iter__()`. You rarely call dunders directly — you implement them and let the syntax dispatch.

**Interview tip:** frame them as 'the

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