解决元类冲突 [英] Resolving metaclass conflicts

问题描述

我需要创建一个根据某些条件使用不同基类的类.在一些课程中，我声名狼藉:

I need to create a class that uses a different base class depending on some condition. With some classes I get the infamous:

TypeError: metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases

一个示例是sqlite3，这是一个甚至可以在解释器中使用的简短示例:

One example is sqlite3, here is a short example you can even use in the interpreter:

>>> import sqlite3
>>> x = type('x', (sqlite3,), {})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases

推荐答案

您可以直接使用:

class M_C(M_A, M_B):
    pass

class C(A, B):
    __metaclass__ = M_C

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