__setattr__,setattr(),getattr__，getattr()及__getattribute__的区别

__setattr__(self,name,value)
#当试图给特性name赋值时候自动被调用，其余方法同理
#相当于触发机制

__getattribute__(self,item)
#每次通过实例化访问属性都会通过该函数
#如果没有该属性，则访问完该函数后，再会通过__getattr__函数

class Book(object):
def __setattr__(self, key, value):
#给特性key赋值时候会被自动调用
if key == 'value1':#当name这个特性是'value1'时
print "key=value1时候跳进来了"
object.__setattr__(self, key, value - 100)#这个value1属性的值value=100，分清value和value1
else:
print "设置时候跳入else了"
object.__setattr__(self, key, value)#正常设置呗
def __getattr__(self, name):
try:
print "__getattr__被调用"
return object.__getattribute__(name)#__getattribute__当name被访问时就被调用
except:
return name + ' is not found!'
def __str__(self):
print "__str__被调用"
return self.name + ' cost : ' + str(self.value1)#这句作用是为了print c的时候显示而已
c = Book()
c.name = 'Python'#这里key = name，value= 'Python'
c.value1 = 100#凡是对属性进行设置的都会进入__setattr__()中
print "---------c.name--------"
print c.name#动态建立属性name，本身在class中不存在，故才调用__getattr__
print "--------c.value1-------"
print c.value1
print "-----------c-----------"
print c
print "---------c.Type--------"
print c.Type#看看有没有Type属性

设置时候跳入else了
key=value1时候跳进来了
---------c.name--------
Python
--------c.value1-------
0
-----------c-----------
__str__被调用
Python cost : 0
---------c.Type--------
__getattr__被调用
Type is not found!

class GSA_atte():
def __init__(self):
self.num = 9
def power(self):
return self.num*self.num
gsa = GSA_atte()#类都要实例化，方法都是对实例进行操作的
print hasattr(GSA_atte(),'num')#相当于有没有num属性,返回布尔类型
print getattr(gsa,'num')#也可以用实例gsa
print getattr(gsa,'y','获取不到y属性')
#getattr(类名,'属性','没有这个属性输出这里')
#也可以用try，except语句来进行包裹代替上句
try:
getattr(gsa,'y')
except:
print('no y')
setattr(gsa,'y',10)#setatta不需要print
print '经过setattr设置参数之后，得到y：',getattr(gsa,'y')

------------hasattr(GSA_atte(),'num')--------- 
True
--------------getattr(gsa,'num')-------------- 
9
--------getattr(gsa,'y','获取不到y属性')-------- 
获取不到y属性
-----------------try--except----------------- 
no y
---------经过setattr设置参数之后，得到y：-------- 
经过setattr设置参数之后，得到y： 10

class C(object):
a = 'abc'
def __getattribute__(self, *args, **kwargs):
print("__getattribute__() is called")
return object.__getattribute__(self, *args, **kwargs)
def __getattr__(self, name):
print("__getattr__() is called ")
return name + " from getattr"
def __get__(self, instance, owner):
print("__get__() is called", instance, owner)
return self
def __call__(self, x):
print("__call__ is called")
print "x :"+str(x)
class C2(object):
d = C()
if __name__ == '__main__':
c = C()
c2 = C2()
print "------------c.a-------------"
print(c.a)
print "---------c.zzzzzz-----------"
print(c.zzzzzz)
print "-----------c2.d-------------"
c2.d
print "-----------c2.d.------------"
print(c2.d.a)#d是作为C2的一个属性被调用
print "----------c(200)------------"
print c(200)

------------c.a-------------
__getattribute__() is called
abc
---------c.zzzzzz-----------
__getattribute__() is called
__getattr__() is called 
zzzzzz from getattr
-----------c2.d-------------
('__get__() is called', <__main__.C2 object at 0x0000000002DA92E8>, <class '__main__.C2'>)
-----------c2.d.------------
('__get__() is called', <__main__.C2 object at 0x0000000002DA92E8>, <class '__main__.C2'>)
__getattribute__() is called
abc
----------c(200)------------
__call__ is called
x :200
None