python - 在python中，frozenset的子类的__init__方法抛出参数编号的TypeError

Question

该类的__init__方法有 3 个参数，但是当我用 3 个参数实例化它时，它会抛出一个错误，它需要 1 个参数。我无法理解。

class ArrObj(frozenset):
    def __init__(self, elem_list, elem_count, self_count):
        super(ArrObj, self).__init__(elem_list)  # Enums, ArrObj, race_id
        self.elem_count = elem_count
        self.self_count = self_count
        assert self_count > 0


if __name__ == '__main__':
    a = ArrObj(['a', 'b', 'c'], {'a':1, 'b':2, 'c':3}, 8)

Traceback (most recent call last):
  File "G:/pycharm-projects/new_keyinfo/verify_treekeys.py", line 34, in <module>
    a = ArrObj(['a', 'b', 'c'], {'a':1, 'b':2, 'c':3}, 8)
TypeError: ArrObj expected at most 1 arguments, got 3

标签： pythonpython-2.7frozenset

Answer 1

frozenset.__init__不需要额外的参数，因为你不能frozenset在它被创建后修改它。（事实上​​，frozenset根本没有定义__init__；它只是使用__init__it 继承自object。）您传递给的可迭代frozenset对象被 by 消耗frozenset.__new__。

class ArrObj(frozenset):
    def __new__(cls, elem_list, elem_count, self_count):
        # May as well assert this before you do any more work
        assert self_count > 0

        obj = super().__new__(cls, elem_list)
        obj.elem_count = elem_count
        obj.self_count = self_count
        return obj