Python----面向对象---反射

一、引子，想根据用户的输入来判断输出的属性

代码如下：

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

    def talk(self):
        print('%s is talking ' % self.name)

obj = People('alex', 29)

# print(obj.name)  # obj.__dict__['name']
# print(obj.talk)

choice = input('>>:')  # choice = 'name'
print(obj.choice)  # print(obj.'name')

结果为：

>>:add
Traceback (most recent call last):
  File "C:/Users/xudachen/PycharmProjects/Python全栈开发/第三模块/面向对象/23 反射.py", line 17, in <module>
    print(obj.choice)  # print(obj.'name')
AttributeError: 'People' object has no attribute 'choice'

结果报错，是因为方式错误，name为字符串，所以说报错，那有没有方法实现呢，这就用到反射方法，如下：

二、通过字符串映射到对象的属性

1、查询是否有某个属性

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

    def talk(self):
        print('%s is talking ' % self.name)

obj = People('alex', 29)

# print(obj.name)  # obj.__dict__['name']
# print(obj.talk)

# choice = input('>>:')  # choice = 'name'
# print(obj.choice)  # print(obj.'name')

print(hasattr(obj, 'name'))  # obj.name # obj.__dict__['name']
print(hasattr(obj, 'talk'))  # obj.talk

结果为：
True
True

True说明有这个属性

2、获取某个属性

print(getattr(obj, 'name'))

结果为：

alex

但是如果没有某个属性，就会报错

print(getattr(obj, 'name123'))

结果为：

Traceback (most recent call last):
  File "C:/Users/xudachen/PycharmProjects/Python全栈开发/第三模块/面向对象/23 反射.py", line 22, in <module>
    print(getattr(obj, 'name123'))
AttributeError: 'People' object has no attribute 'name123'

如果不让让他报错，可以加一个default参数，例如None

print(getattr(obj, 'name123', None))

结果为;

None

获取函数属性;

print(getattr(obj, 'talk', None))

结果为;

<bound method People.talk of <__main__.People object at 0x0000028F3FD2B358>>

3、设置某个属性

setattr(obj, 'sex', 'male')  # obj.sex = 'male'
print(obj.sex)

结果为;

male

4、删除某个属性

delattr(obj, 'age')  # del obj.age
print(obj.__dict__)

结果为：

{'name': 'alex'}

5、对类来说，是类似的，也可以获取某个属性，例如数据属性和函数属性

print(getattr(People, 'country'))  # People.country

结果为：

China