当前python 3的更新如下：class MC(type):

def __repr__(self):

return 'Wahaha!'

class C(object, metaclass=MC):

pass

print(C)

如果希望跨python 2和python 3运行的代码，则six模块将包含以下内容：from __future__ import print_function

from six import with_metaclass

class MC(type):

def __repr__(self):

return 'Wahaha!'

class C(with_metaclass(MC)):

pass

print(C)

最后，如果你有一个想要自定义静态，的类，基于上面的类的方法很有效，但是如果有几个，则必须生成类似于MC的类类似于，并且可以使用，from __future__ import print_function

from six import with_metaclass

def custom_class_repr(name):

"""

Factory that returns custom metaclass with a class ``__repr__`` that

returns ``name``.

"""

return type('whatever', (type,), {'__repr__': lambda self: name})

class C(with_metaclass(custom_class_repr('Wahaha!'))): pass

class D(with_metaclass(custom_class_repr('Booyah!'))): pass

class E(with_metaclass(custom_class_repr('Gotcha!'))): pass

print(C, D, E)

打印：Wahaha! Booyah! Gotcha!

元编程并不是你每天都需要的东西，但是当你需要它的时候，它真的很适合你！