【python】-- 类的反射

反射

反射我们以后会经常用到,这个东西实现了动态的装配,通过字符串来反射类中的属性和方法

 一、反射函数

1、hasarttr(obj,name_str)

作用:判断一个对象obj中是否有对应的name_str字符串的属性或者方法

class Dog(object):
 
    def __init__(self,name):
        self.name = name
 
    def eat(self,food):
        print("{0} is eating...{1}".format(self.name,food))
 
d = Dog("shabi")
choice = input(">>>:").strip()
 
print(hasattr(d,choice))  #obj中是否有对应的choice字符串的属性或者方法
 
#输出
>>>:name  #输入对象存在属性
True
>>>:eat  #输入对象存在的方法
True

  

2、getattr(obj,name_str)

作用:根据字符串name_str获取obj对象中的对应方法的内存地址或者对应属性的值

class Dog(object):
 
    def __init__(self,name):
        self.name = name
 
    def eat(self,food):
        print("{0} is eating...{1}".format(self.name,food))
 
d = Dog("shabi")
choice = input(">>>:").strip()
 
print(getattr(d,choice))  #choice获取obj对象中的对应方法的内存地址或者对应属性的值
 
#输出
>>>:name  #返回name属性的值
shabi
>>>:eat
<bound method Dog.eat of <__main__.Dog object at 0x00000157A129CF28>>  #返回eat方法的内存地址

  

3、setattr(x,y,z)

作用:给obj对象添加一个新属性或者新方法,setattr(x, 'y', v) is equivalent to ``x.y = v''

①给对象新增一个新方法

def bulk(self):  #先定义一个bulk函数
    print("{0} is yelling...".format(self.name))
 
class Dog(object):
 
    def __init__(self,name):
        self.name = name
 
    def eat(self,food):
        print("{0} is eating...{1}".format(self.name,food))
 
d = Dog("shabi")
choice = input(">>>:").strip()
 
setattr(d,choice,bulk)  #输入的是talk,所以又等同于d.talk = bulk
#d.talk(d) 直接写死,用d.talk(d),一般不这么写
func = getattr(d,choice) #用getattr来获取
func(d)
 
#输出
>>>:talk
shabi is yelling...

②给对象新增一个属性

class Dog(object):
 
    def __init__(self,name):
        self.name = name
 
    def eat(self,food):
        print("{0} is eating...{1}".format(self.name,food))
 
d = Dog("shabi")
choice = input(">>>:").strip()
 
setattr(d,choice,22)  #输入的是age,所以又等同于d.age = 22
# print(d.age) 这样就写死了,还是用下面一种
print(getattr(d,choice))
 
#输出
>>>:age
22

 

4、delattr(x,y)

 作用:删除obj对象中的属性或者方法,delattr(x, 'y') is equivalent to ``del x.y''

class Dog(object):
 
    def __init__(self,name):
        self.name = name
 
    def eat(self,food):
        print("{0} is eating...{1}".format(self.name,food))
 
d = Dog("shabi")
choice = input(">>>:").strip()
 
delattr(d,choice) #根据字符串删除属性或者方法
print(d.name)
print(d.eat)
 
#输出
>>>:name   #删除属性name
Traceback (most recent call last):
  File "E:/PycharmProjects/pythontest/day7/反射/反射.py", line 22, in <module>
    print(d.name)
AttributeError: 'Dog' object has no attribute 'name'
>>>:eat   #删除方法eat
Traceback (most recent call last):
  File "E:/PycharmProjects/pythontest/day7/反射/反射.py", line 21, in <module>
    delattr(d,choice)
AttributeError: eat

 

5、综合使用hasattr、getattr、setattr

class Dog(object):
 
    def __init__(self,name):
        self.name = name
 
    def eat(self,food):
        print("{0} is eating...{1}".format(self.name,food))
 
d = Dog("shabi")
choice = input(">>>:").strip()
 
if hasattr(d,choice):  #判断d对象中存在属性和方法
    name_value = getattr(d,choice)  #获取属性值
    print(name_value)
    setattr(d,choice,"hong")   #修改属性值
    print(getattr(d,choice))   #重新获取属性的值
else:
    setattr(d,choice,None)    #设置不存在的属性值为None
    v = getattr(d,choice)
    print(v)
 
#输出
>>>:name
shabi
hong
>>>:abc
None

 

posted @ 2017-08-10 13:20  Wilson_Blogs  阅读(329)  评论(0编辑  收藏  举报