45.魔法方法：属性访问

class Rectangle:
    def __init__(self, width=0, height=0):
        self.width = width
        self.height = height

    def __setattr__(self, name, value):
        if name == 'square':
            self.width = value
            self.height = value
        else:
            # super().__setattr__(name, value)   # 方法1
            self.__dict__[name] = value          # 方法2,此两法相同

    def getArea(self):
        return self.width * self.height

结果

>>> r1 = Rectangle(4,5)
>>> r1.square = 10
>>> r1.height
10
>>> r1.width
10
>>> r1.getArea()
100
>>> r1.__dict__
{'width': 10, 'height': 10}