python: hassttr/getattr/setattr方法使用

class function_demo(object):
    __name = 'demo'
    name = 'ok'
    def run(self):
        print("hello function")

# hasattr

functiondemo = function_demo()
# res = hasattr(functiondemo, '__name')  #判断对象是否有__name 属性，True
# res = hasattr(functiondemo, 'name')  #判断对象是否有__name 属性，True
# res = hasattr(functiondemo, "run") #判断对象是否有run方法，True
# res = hasattr(functiondemo, "age") #判断对象是否有age属性，False
# print(res)


# getattr

# print(getattr(functiondemo, 'name', 'bad'))# 获取name属性，存在就打印出来--- ok
# # print(getattr(functiondemo, '__name'))# 获取__name属性，报错:AttributeError: 'function_demo' object has no attribute '__name'
# print(getattr(functiondemo, '__dir__'))# <built-in method __dir__ of function_demo object at 0x0000000001E46A90>
# print(getattr(functiondemo, "run"))# 获取run方法，存在打印出 方法的内存地址---<bound method function_demo.run of <__main__.function_demo object at 0x10244f320>>
# getattr(functiondemo, "run")()# hello function
#
# try:
#     getattr(functiondemo, "age")
# except Exception as e:
#     print(e) # 'function_demo' object has no attribute 'age'
#
# print(getattr(functiondemo, "age", 18))  #获取不存在的属性，返回一个默认值18

# setattr

# print(hasattr(functiondemo, 'age')) # 判断age属性是否存在，False
# print(setattr(functiondemo, 'age', 18)) # 对age属性进行赋值，无返回值
# setattr(functiondemo, 'square', lambda x: x*x) # 对square属性定义匿名函数
# print(hasattr(functiondemo, 'age')) # 再次判断属性是否存在，True
# print(getattr(functiondemo, 'square')(2)) # 得到值4

# setattr(functiondemo, '__age', 18)
# print(getattr(functiondemo, '__age')) # 得到结果18