python 元类型编程，实现匿名验证器的装饰器AuthenticationDecoratorMeta

metaclass，元类

metaclass是这样定义的：In object-oriented programming, a metaclass is a class whose instances are classes. Just as an ordinary class defines the behavior of certain objects, a metaclass defines the behavior of certain classes and their instances.

metaclass的实例化结果是类，而class实例化的结果是instance。metaclass是创建类的模板，所有的类都是通过他来create的(调用__new__)，你可以定创建类的独特行为，实现你所需要的特殊功能。

type 也是metalclass的一种元类。

通过派生type的子类，来实现类创建过程中的特殊行为。

type的构造函数：type.__new__(cls, name, bases, dct)

cls: 将要创建的类，类似与self，但是self指向的是instance，而这里cls指向的是class

name: 类的名字

bases: 基类，通常是tuple类型

attrs: dict类型，就是类的属性或者函数

实现为类的方法，进行匿名验证的metaclass， ----AuthenticationDecoratorMeta

源码：

from types import FunctionType

def Authentication(func):
print 'Execute validition Successfully!'
return func

class AuthenticationDecoratorMeta(type):
def __new__(cls, name, bases, dct):
for name, value in dct.iteritems():
if name not in ('__metaclass__', '__init__', '__module__') and \
type(value) == FunctionType:
value = Authentication(value)
dct[name] = value
return type.__new__(cls, name, bases, dct)

class Login(object):
__metaclass__ = AuthenticationDecoratorMeta

def Delete(self, x):
print 'Delete ', x

def main():
login = Login()
login.Delete('xxxx')
if __name__ == '__main__':
main()

运行效果如下：

Execute validition Successfully!
Delete  xxxx