Python 3 Deep Dive Part 4 Oop High Quality

from dataclasses import dataclass, field

class X: pass class Y: pass class Z: pass class A(X, Y): pass class B(Y, Z): pass class M(A, B, Z): pass

class PositiveInt(int): def (cls, value): if value <= 0: raise ValueError("PositiveInt must be > 0") return super(). new (cls, value)

@width.setter def width(self, value): self._width = value self._height = value # Breaks Rectangle's contract!

class Temperature: def __init__(self, celsius): self._celsius = celsius @property def celsius(self): return self._celsius

High-quality classes behave like native types. If you have a mathematical object, it should support + and - .