反射

概述

反射实现动态装配，通过字符串来反射类中的属性和方法

反射函数

1、hasattr(obj,name_str)           作用：判断一个对象obj是否存在name_str的属性或者方法

class Dog(object):
    def __init__(self, name):
        self.name = name

    def eat(self):
        print("%s eating...."% self.name)
d = Dog("JJ")
choice = input(">>>").strip()
print(hasattr(d, choice))

结果：
>>>ss
False

或者

>>>eat
True

 

2、getattr(obj, name_str)        作用：根据字符串name_str获取obj对象中的内存地址或者对应的属性值

class Dog(object):
    def __init__(self, name):
        self.name = name

    def eat(self):
        print("%s eating...."% self.name)
d = Dog("JJ")
choice = input(">>>").strip()
if hasattr(d, choice):
    print(getattr(d,choice))   # 通过choice输入的字符串从d对象里寻找


结果：
>>>eat
<bound method Dog.eat of <__main__.Dog object at 0x0053C2F0>>

 3、setattr(x,y,z)       作用：给obj添加一个新的属性或者方法

1）给对象新增一个方法

def bulk(self):
    print("%s is yelling"% self.name)


class Dog(object):
    def __init__(self, name):
        self.name = name

    def eat(self):
        print("%s eating...."% self.name)
d = Dog("JJ")
choice = input(">>>").strip()
setattr(d, choice, bulk)
# d.talk(d)  # 直接写死了，一般不用这种
func = getattr(d, choice) # 用getattr来获取
func(d)

结果：
>>>talk
JJ 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):
        print("%s eating...."% self.name)
d = Dog("JJ")
choice = input(">>>").strip()
setattr(d, choice, 22)
# print(d.age)  #直接写死了  一般不这么写
print(getattr(d, choice))

结果：
>>>number
22

4、delattr(x, y)     作用：删除obj对象中的属性和方法，delattr(x, 'y') is equivalent to ``del x.y''

class Dog(object):
    def __init__(self, name):
        self.name = name

    def eat(self):
        print("%s eating...."% self.name)
d = Dog("JJ")
choice = input(">>>").strip()
delattr(d, choice)
print(d.eat)
print(d.name)

结果：
>>>eat
Traceback (most recent call last):
  File "E:/python_3.5/stu/反射模块.py", line 14, in <module>
    delattr(d, choice)
AttributeError: eat

1、hasattr

2、getattr

3、setattr

4、delattr

1)添加一个新方法

def bulk(self):
    print("yelling......")

class Dog(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def eat(self, food):
        print("%s eating....%s"%(self.name, food))

d = Dog("Lidy", 2)
choice = input(">>>")
if hasattr(d, choice):
    fun = getattr(d, choice)
    fun("baozi")
else:
    setattr(d, choice, bulk)
    # print(getattr(d, choice))
    fun = getattr(d, choice)
    fun(d)


结果：
>>>talk
yelling......

或者
>>>eat
Lidy eating....baozi

2）添加新的属性

def bulk(self):
    print("yelling......")

class Dog(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def eat(self, food):
        print("%s eating....%s"%(self.name, food))

d = Dog("Lidy", 2)
choice = input(">>>")
if hasattr(d, choice):
    attr = getattr(d, choice) 
else:
    setattr(d, choice, 222)

print(getattr(d, choice))

结果：
>>>name
Lidy

或者
>>>eee
222

3）删除属性

def bulk(self):
    print("yelling......")

class Dog(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def eat(self, food):
        print("%s eating....%s"%(self.name, food))

d = Dog("Lidy", 2)
choice = input(">>>")
if hasattr(d, choice):
    delattr(d, choice)
    # attr = getattr(d, choice)
else:
    setattr(d, choice, 222)

print(getattr(d, choice))
    # fun = getattr(d, choice)
    # fun(d)

结果：
>>>name
Traceback (most recent call last):
  File "E:/python_3.5/stu/类/反射.py", line 22, in <module>
    print(getattr(d, choice))
AttributeError: 'Dog' object has no attribute 'name'