1. 修改类函数。

场景： 如果要给一个类的所有方法加上计时，并打印出来。demo如下：

# -*- coding:utf-8 -*-import timedef time_it(fn):    "Example of a method decorator"    def decorator(*args, **kwargs):    t1=time.time()        ret = fn(*args, **kwargs)    print '\t\t%d seconds taken for %s'%(time.time()-t1, fn.__name__)    return ret    return decoratordef class_decorator(*method_names):    def class_rebuilder(cls):        "The class decorator example"        class NewClass(cls):            "This is the overwritten class"            def __getattribute__(self, attr_name):                attr_val = super(NewClass, self).__getattribute__(attr_name)                if callable(attr_val) and attr_name in method_names:                    return time_it(attr_val)                return attr_val        return NewClass    return class_rebuilder@class_decorator('first_method', 'second_method')class MySecondClass(object):    """    This class is decorated    """    def first_method(self, *args, **kwargs):        print "\tthis is a the MySecondClass.first_method"    time.sleep(2)    def second_method(self, *args, **kwargs):        print "\tthis is the MySecondClass.second_method"    time.sleep(1)if __name__ == "__main__":    print "::: With a decorated class :::"    z = MySecondClass()    z.first_method()    z.second_method()

 

好处相比函数修饰器要稍微简洁一点（在类有很多方法时）

 

2. 增加类成员

场景：比如统一给所有的模型增加id, created_time属性

# -*- coding:utf-8 -*-def addAttrs(*attrs):    def re_build(cls):        class newClass(cls):            def __init__(self,*args, **kws):                for attr in attrs:            setattr(self, attr, None)                self.__id = id                super(newClass, self).__init__(*args, **kws)        return newClass    return re_build@addAttrs('id', 'created_time')class DBModelOne(object):    def __init__(self, *args, **kwargs):        passif __name__=='__main__':    m = DBModelOne(5)    print m.id, m.created_time

 

or

# -*- coding:utf-8 -*-import timedef cd(cls):    def init(*args, **kwargs):        cls_obj = cls(*args, **kwargs)        setattr(cls_obj, 'id', time.time())        return cls_obj    return init@cdclass A(object):    def __init__(self, name, age, sex='f'):        self.name=name        self.age=age        self.sex=sex    def s(self):        print self.idif __name__=='__main__':    print type(A)#
     
          a=A('Alice', 22)    print type(a)#
      
           print a#<__main__.A object at 0x7fe617baa690>    print a.name, a.age, a.sex#Alice 22 f    a.s()
      
     

 

 

转载请注明来自：http://www.cnblogs.com/Tommy-Yu/p/5457751.html