Python3.7：元组基础 class 的元分类，接收类型错误

Question

I am trying to create metaclass:

from typing import Tuple

class StructMeta(Tuple):
    pass

class Struct(metaclass=StructMeta):
    pass

print(type(Struct))

Execute:

Traceback (most recent call last):
File "main.py", line 9, in <module>
class Struct(metaclass=StructMeta):
TypeError: tuple expected at most 1 argument, got 3

Do not understand why this error?

Answer 1

typing.Tuple appears to be a subclass of tuple , which only takes one argument, an iterable.

When creating a class, Python passes 3 arguments to its metaclass: the class name, a tuple of base classes, and a dict representing the class body.

It's not really possible to use typing.Tuple as a metaclass.