Python中hasattr(),getattr(),setattr()的用法介绍（代码示例）

1、hasattr(object, name)

　　判断object里是否有name属性，有就返回True，没有则返回False。

class MyClass(object):
 name = 'jack'
 age = '22'


obj = MyClass()
print(hasattr(obj, 'name')) # True
print(hasattr(MyClass, 'age')) # True
print(hasattr(obj, 'gender')) # False

2. getattr(object, name, [default])

用来获取object的属性或方法,有就打印出来. 没有就打印默认值,若是没有设置默认值则报错

class MyClass(object):
 name = 'jack'
 age = '22'

 def func(self):
 return 'hello world!!!'


obj = MyClass()

print(getattr(MyClass, 'name')) # jack
print(getattr(obj, 'age')) # 22
print(getattr(MyClass, 'func')) # <function MyClass.func at 0x000001ACDE9A9AE8>
print(getattr(obj, 'func')) # <bound method MyClass.func of <__main__.MyClass object at 0x000001D1505D01D0>>
# print(getattr(MyClass, 'func1')) # 没有设置默认值,找不到方法会报错: AttributeError: type object 'MyClass' has no attribute 'func1'
print(getattr(MyClass, 'func1', None)) # 设置了默认值None,找不到就会返回默认值: None

print(getattr(MyClass, 'func')('self')) # hello world!!!
print(getattr(obj, 'func')()) # hello world!!!

3. setattr(object, key, value)

用来对object的属性key赋值value. 若是key存在,则更新value的值. 若key不存在,则先创建属性key再对其赋值value.

class MyClass(object):
 name = 'jack'
 age = '22'


obj = MyClass()

setattr(MyClass, 'name', 'tom')
print(getattr(MyClass, 'name')) # tom

setattr(obj, 'age', 28)
print(getattr(obj, 'age')) # 28

setattr(MyClass, 'gender', 'male')
print(getattr(MyClass, 'gender')) # male
print(getattr(obj, 'gender')) # male

setattr(obj, 'hobby', 'skating')
print(obj, 'hobby') # <__main__.MyClass object at 0x00000209F5070630> hobby
print(MyClass, 'hobby') # <class '__main__.MyClass'> hobby

三个方法一起用:

class MyClass(object):
 name = 'jack'
 age = '22'


# 判断Myclass是否有gender属性,有则打印,没有则添加
def if_attr(gender='male'):
 if hasattr(MyClass, 'gender'):
 return getattr(MyClass, 'gender')
 return setattr(MyClass, 'gender', gender)


if_attr(gender='female')
print(getattr(MyClass, 'gender')) # female