在python中了解多个类的__new__和__init__

Question

所以我创建了两个元组的子类，并希望根据某些条件创建一个或另一个。我知道工厂模式，这将是适当的解决方案，但在我的具体情况下，我不能使用它 - 坦率地说，我想了解:) 更具体地说，我想知道在通过__init__创建对象后何时调用__new__以及何时（以及为什么）创建对象。

以下代码示例应说明我尝试实现的目标：

class my_special_interval(tuple):
    def __init__(self,a,b):
        print("my_special_interval")
        self.a = a
        self.b = b
    def __new__(cls, a, b):
        if a > b:
            return super(my_special_interval, cls).__new__(my_special_interval, (a, b))
        else:
            obj = super(my_special_interval, cls).__new__(my_second_special_interval, (a, b))
            print("Explicit init necessary:")
            obj.__init__(a,b)
            return obj


class my_second_special_interval(tuple):
    def __init__(self,a,b):
        print("my_second_special_interval")
        self.a = a
        self.b = b

    def __new__(cls, a, b):
        if a > b:
            obj = super(my_second_special_interval, cls).__new__(my_special_interval, (a, b))
            print("Explicit init necessary:")
            obj.__init__(a,b)
        else:
            return super(my_second_special_interval, cls).__new__(my_second_special_interval, (a, b))

if __name__ == '__main__':
    a = 2.0
    b = 1.0
    iv1 = my_special_interval(a,b)

    a = 1.0
    b = 2.0
    iv2 = my_special_interval(a,b)


    a = 2.0
    b = 1.0
    iv1 = my_second_special_interval(a,b)

    a = 1.0
    b = 2.0
    iv2 = my_second_special_interval(a,b)

这导致以下打印输出：

my_special_interval
Explicit init necessary:
my_second_special_interval
Explicit init necessary:
my_special_interval
my_second_special_interval

THX，

垫