如何派生内置不可变类型并修改其实例化行为？

需求：
我们想自定义一种新类型的元组，对于传入的可迭代对象，我们只保留作其中int类型且值大于0的元素，例如：
IntTuple([1,-1,'abc',6,['x','y'],3]) => (1,6,3)
要求IntTuple是内置tuple的子类，如何实现？

思路：
定义IntTuple继承内置tuple，并实现__new__，修改实例化行为（即创建self的行为）

代码：

class IntTuple(tuple):
    def __new__(cls,iterable): # cls为类对象的父类，在python中类也是对象
        g = (x for x in iterable if isinstance(x,int) and x > 0)
        return super(IntTuple,cls).__new__(cls,g) # 返回一个类对象，这个类对象传给下面__init__()方法中的self。

    def __init__(self,iterable):
        print(self) # 返回类实例对象本身
        super(IntTuple,self).__init__()


t = IntTuple([1,-1,'abc',6,['x','y'],3])
print(t)

=================================================================

class IntTuple(tuple):
    def __new__(cls,iterable):
        # 过滤iterable
        f_it = ( e for e in iterable if isinstance(e,int) and e > 0)
        return super().__new__(cls,f_it)



int_t = IntTuple([1,-1,'abc',6,['x','y'],3])
print(int_t)

========================================================================
>>> class A:
...     def __new__(cls,*args):
...         print('In A.__new__',cls,args)
...         return object.__new__(cls)
...     def __init__(self,*args):
...         print('In A.__init__',args)
... 

>>> # a = A(1,2)

>>> a = A.__new__(A,1,2)
In A.__new__ <class '__main__.A'> (1, 2)

>>> a
<__main__.A at 0x7f91ca002908>

>>> A.__init__(a,1,2)
In A.__init__ (1, 2)

>>> list('abc')
['a', 'b', 'c']

>>> l = list.__new__(list,'abc')

>>> l
[]

>>> list.__init__(l,'abc')

>>> l
['a', 'b', 'c']

>>> tuple('abc')
('a', 'b', 'c')

>>> t = tuple.__new__(tuple,'abc')

>>> t
('a', 'b', 'c')

>>> tuple.__init__(t,'abc')

>>> tuple.__init__ is object.__init__
True

>>> list.__init__ is object.__init__
False

>>>