14、Python之反射

一、反射

   反射的本质是：通过知道对象属性或方法的字符串形式，就能够访问该对象的属性和方法的过程。

1、检查对象是否有某个属性或方法，使用hasattr。

class Dog(object):
    def __init__(self,name):
        self._name = name
    def bark(self):
        print("%s is barking" % self._name)

d = Dog("lido")
print(hasattr(d,"bark")) #True -  有bark方法
print(hasattr(d,"bark1"))#False - 无bark1方法
print(hasattr(d,"_name"))#True  -  有_name属性

2、通过属性或方法的字符串形式获得属性的值或方法的地址，使用getattr。

class Dog(object):
    def __init__(self,name):
        self._name = name
    def bark(self):
        print("%s is barking" % self._name)

d = Dog("lido")
bark_address = getattr(d,"bark")#通过bark的字符串返回其地址
bark_address()
name_01 = getattr(d,"_name")
print(name_01)

3、给对象动态添加属性或者方法，使用setattr

def run(name):
    print("%s is running" % name)

class Dog(object):
    def __init__(self,name):
        self._name = name
    def bark(self):
        print("%s is barking" % self._name)

d = Dog("lido")
setattr(d,"_age",20)
setattr(d, 'run',run)
print(d._age)
d.run(d._name)

4、动态删除对象的属性或者方法，使用delattr。

class Dog(object):
    def __init__(self,name):
        self._name = name
    def bark(self):
        print("%s is barking" % self._name)

d = Dog("lido")
delattr(d,"bark")
delattr(d,"_name")
d.bark()
print(d._name)

5、如果只知道一个类的字符串形式，如何来创建类对象呢，方法有很多这里暂时先介绍一种，使用globals方法，这个方法返回一个字典，以类名的字符串作为key，地址作为value。代码如下：

class Dog(object):
    def __init__(self,name):
        self._name = name
    def bark(self):
        print("%s is barking" % self._name)

D = globals()["Dog"]
d = D("go")
d.bark()

6、综合实例

class Dog(object):
    def __init__(self):
        # self._name = name
        pass
    def bark(self):
        print("%s is barking" % self._name)
    def run(self):
        print("%s is running" % self._name)
    def sleep(self):
        print("%s is sleeping" % self._name)
    def print_self(self):
        print("my name is %s" % self._name)
d = Dog()
setattr(d,"_name",input("请输入狗的姓名>>"))
while True:
    choice = input("1、bark,1、run,3、sleep,4、print_selft")
    if choice == '1':
        break
    if hasattr(d,choice):
        getattr(d,choice)()
    else:
        print("输入错误")