python如何派生内置不可变类型并修改实例化行为

#!/usr/bin/python3
 
 
class IntTuple(tuple):
  def __new__(cls, iterable):
    # new方法是init方法之前进行调用的方法
    # 生成一个生成式
    g = (x for x in iterable if isinstance(x, int) and x > 0)
     
    # cls为这个类本身，把参数g交给这个类本身
    return super(IntTuple, cls).__new__(cls, g)
 
  def __init__(self, iterable):
    pass
     
     
if __name__ == "__main__":
  l = [1, -2, 'xxx', 7, [1, 'oo'], 9]
   
  result = IntTuple(l)
  print(result)