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 time
def 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 decorator def 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):
pass if __name__=='__main__':
m = DBModelOne(5)
print m.id, m.created_time
or
# -*- coding:utf-8 -*-
import time
def cd(cls):
def init(*args, **kwargs):
cls_obj = cls(*args, **kwargs)
setattr(cls_obj, 'id', time.time())
return cls_obj
return init
@cd
class A(object):
def __init__(self, name, age, sex='f'):
self.name=name
self.age=age
self.sex=sex
def s(self):
print self.id if __name__=='__main__':
print type(A)#<type 'function'>
a=A('Alice', 22)
print type(a)#<class '__main__.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