Các dunder methods quan trọng nhất cần biết?

1. __repr__ — developer repr (eval-safe), __str__ — user-friendly string
2. __len__, __getitem__, __setitem__ — sequence protocol
3. __enter__/__exit__ — context manager
4. __eq__, __lt__, __hash__ — comparison và hashability
5. __call__ — cho phép gọi instance như function
6. __iter__/__next__ — iterator protocol

Lưu ý: Khi override __eq__, Python tự động set __hash__ = None — phải define __hash__ thủ công nếu muốn dùng object trong set/dict.

1. __repr__ — developer repr, __str__ — user string
2. __len__, __getitem__ — sequence protocol
3. __enter__/__exit__ — context manager
4. __eq__, __hash__ — comparison
5. __call__ — callable instances
6. __iter__/__next__ — iterator

Pitfall: Overriding __eq__ sets __hash__ = None — must define __hash__ manually if needed in sets/dicts.