为什么我不能在 python3 中子类化元组？

让我们先说一下这个问题你应该使用__new__代替__init__用于子类化不可变对象 https://stackoverflow.com/questions/399022/why-cant-i-subclass-datetime-date.

话虽如此，让我们看看下面的代码：

class MyTuple(tuple):
    def __init__(self, *args):
        super(MyTuple, self).__init__(*args)

mytuple = MyTuple([1,2,3])

这在 python2 中有效，但在 python3 中我得到：

Traceback (most recent call last):
  File "tmp.py", line 5, in <module>
    mytuple = MyTuple([1,2,3])
  File "tmp.py", line 3, in __init__
    super(MyTuple, self).__init__(*args)
TypeError: object.__init__() takes no parameters

为什么会出现这种情况？ python3 发生了什么变化？

Python 3 改变了哪些方式object.__new__ and object.__init__当两者都被覆盖时对参数做出反应。如果一个类重写（或继承重写的方法）两者object.__init__ and object.__new__, object.__init__ and object.__new__如果他们收到任何多余的参数，就会抛出异常。在 Python 2 中，这会给出 DeprecationWarning（默认情况下禁止）。

tuple没有自己的__init__。它继承了object.__init__，所以你实际上传递了一堆参数object.__init__ that object.__init__不需要。 Python 2 给你一个（抑制的）警告，而 Python 3 让它成为一个错误。

代码中有注释，很好地解释了object.__init__ and object.__new__对额外参数的微妙处理：

/* You may wonder why object.__new__() only complains about arguments
   when object.__init__() is not overridden, and vice versa.

   Consider the use cases:

   1. When neither is overridden, we want to hear complaints about
      excess (i.e., any) arguments, since their presence could
      indicate there's a bug.

   2. When defining an Immutable type, we are likely to override only
      __new__(), since __init__() is called too late to initialize an
      Immutable object.  Since __new__() defines the signature for the
      type, it would be a pain to have to override __init__() just to
      stop it from complaining about excess arguments.

   3. When defining a Mutable type, we are likely to override only
      __init__().  So here the converse reasoning applies: we don't
      want to have to override __new__() just to stop it from
      complaining.

   4. When __init__() is overridden, and the subclass __init__() calls
      object.__init__(), the latter should complain about excess
      arguments; ditto for __new__().

   Use cases 2 and 3 make it unattractive to unconditionally check for
   excess arguments.  The best solution that addresses all four use
   cases is as follows: __init__() complains about excess arguments
   unless __new__() is overridden and __init__() is not overridden
   (IOW, if __init__() is overridden or __new__() is not overridden);
   symmetrically, __new__() complains about excess arguments unless
   __init__() is overridden and __new__() is not overridden
   (IOW, if __new__() is overridden or __init__() is not overridden).

   However, for backwards compatibility, this breaks too much code.
   Therefore, in 2.6, we'll *warn* about excess arguments when both
   methods are overridden; for all other cases we'll use the above
   rules.

*/