python - python中的多个构造函数

Question

如何将以下 2 个类合并为一个类 Rectangle，以便可以通过 rect = Rectangle(side_a, side_b) 或 rect = Rectangle(side_a, area) 创建一个 Rectangle 对象？

class Rectangle1:
    def __init__(self, side_a, side_b):
        self.side_a = side_a
        self.side_b = side_b
        self.area = self.side_a * self.side_b

class Rectangle2:
    def __init__(self, side_a, area):
        self.side_a = side_a
        self.area = area
        self.side_b = self.area / side_a

Answer 1

如图所示here .

class Rectangle:

    def __init__(self, a, b):
        """ Create a new rectangle with sides of length a and b.
        """
        self.side_a = side_a
        self.side_b = side_b
        self.area = self.side_a * self.side_b

    @classmethod
    def from_sides(cls, a, b):
        return cls(a, b)

    @classmethod
    def from_area(cls, a, o):
        return cls(a, o/a)

然后您可以将矩形创建为

r1 = Rectangle.from_sides(s1, s2)
r2 = Rectangle.from_area(s1, a)