如何理解Python装饰器?

        print ":
        print "def inject_check(method)，如上面代码中的hello函数加上@inject_check装饰器.hello()
就是在函数上加个包装:
#    def hello(self);
    return my_method
############################    
#class Demo(object)，等价于将函数hello重新赋值;hello":
#        print ":
    def my_method(*args);
        method(*args)
        print ":
    @inject_check
    def hello(self);before"after"
#    hello=inject_check(hello)
##########################
    
class Demo(object);hello"
        
d = Demo()
d