反射

反射实现了动态的装配，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)

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("Bone")
C = input(">>>:").strip()
print(hasattr(D , C)) #obj中是否有对应的choice字符串的属性或者方法
#结果
>>>: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)

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("Bone")
C = input(">>>:").strip()
print(getattr(D , C)) #C获取obj对象中的对应方法的内存地址或者对应属性的值

# 结果
>>>:eat  #返回eat方法的内存地址
<bound method Dog.eat of <__main__.Dog object at 0x10f611518>>
>>>:name  #返回name属性的值
Bone

3、setattr(x,y,z)

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 eat(self):
    print("{0} is eating".format(self.name))
class Dog(object):
    def __init__(self,name):
        self.name = name


    def drink(self,food):
        print("{0} is drinking {1}".format(self.name , food))
d = Dog("pengpeng")
c = input(">>>:").strip()
setattr(d,c,eat) #输入的是talk，所以又等同于d.talk = eat
#d.talk(d) 直接写死，用d.talk(d),一般不这么写
func = getattr(d,c) #用getattr来获取
func(d)
#结果
>>>:eat
pengpeng is eating
>>>:talk
pengpeng is eating

②给对象新增一个属性

class Dog(object):
    def __init__(self,name):
        self.name = name
    def drink(self,food):
        print("{0} is drinking {1}".format(self.name , food))
d = Dog("pengpeng")
c = input(">>>:").strip()
setattr(d,c,18)  #输入的是age，所以又等同于d.age = 18
print(getattr(d,c))
#结果
>>>:age
18

　4、delattr(x,y)

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 drink(self,food):
        print("{0} is drinking {1}".format(self.name , food))
d = Dog("pengpeng")
c = input(">>>:").strip()
delattr(d,c)  #根据字符串删除属性或者方法
print(getattr(d,c))
print(d.name)
print(d.drink)
#结果
>>>:drink  #删除方法drink
Traceback (most recent call last):
  File "/Users/bianbian/PycharmProjects/test/71320h.py", line 9, in <module>
    delattr(d,c)  #根据字符串删除属性或者方法
AttributeError: drink

>>>:name #删除属性name
Traceback (most recent call last):
  File "/Users/bianbian/PycharmProjects/test/71320h.py", line 10, in <module>
    print(getattr(d,c))
AttributeError: 'Dog' object has no attribute 'name'

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("pengpeng")
c = input(">>>:").strip()
if hasattr(d,c):  #判断d对象中存在属性和方法
    name_value = getattr(d,c) #获取属性值
    print(name_value)
    setattr(d,c,"bianbian") #修改属性值
    print(getattr(d,c)) #重新获取属性的值
else:
    setattr(d,c,None) #设置不存在的属性值为None
    v = getattr(d,c)
    print(v)
#结果
>>>:name
pengpeng
bianbian

>>>:bb
None