Shouldn't __metaclass__ force the use of a metaclass in Python?

Question

I\'ve been trying to learn about metaclasses in Python. I get the main idea, but I can\'t seem to activate the mechanism. As I understand it, you can specify M to be as the

Answer 1

The syntax of metaclasses has changed in Python 3.0. The __metaclass__ attribute is no longer special at either the class nor the module level. To do what you're trying to do, you need to specify metaclass as a keyword argument to the class statement:

p = print

class M(type):
    def __init__(*args):
        type.__init__(*args)
        print("The rain in Spain")

p(1)
class ClassMeta(metaclass=M): pass

Yields:

1
The rain in Spain

As you'd expect.