问题子类化内置类型 [英] problem subclassing builtin type

问题描述

# Python 3
class Point(tuple):
    def __init__(self, x, y):
        super().__init__((x, y))

Point(2, 3)

会导致

TypeError:tuple()最多需要1个 论点(给出2个)

TypeError: tuple() takes at most 1 argument (2 given)

为什么?我该怎么办?

推荐答案

tuple是不可变的类型.它甚至在调用__init__之前就已经创建并且不可变.这就是为什么这行不通的原因.

tuple is an immutable type. It's already created and immutable before __init__ is even called. That is why this doesn't work.

如果您真的想对元组进行子类化，请使用 __new__ .

If you really want to subclass a tuple, use __new__.

>>> class MyTuple(tuple):
...     def __new__(typ, itr):
...             seq = [int(x) for x in itr]
...             return tuple.__new__(typ, seq)
... 
>>> t = MyTuple((1, 2, 3))
>>> t
(1, 2, 3)

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