Python的hasattr(),getattr(),setattr()

1. hasattr(object, name)

　　判斷object裏是否有name屬性，有就返回True，沒有則返回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])

用來獲取object的屬性或方法,有就打印出來. 沒有就打印默認值,如果沒有設置默認值則報錯

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'))  # 沒有設置默認值,找不到方法會報錯: AttributeError: type object 'MyClass' has no attribute 'func1'
print(getattr(MyClass, 'func1', None))  # 設置了默認值None,找不到就會返回默認值: None

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

3. setattr(object, key, value)

用來對object的屬性key賦值value. 如果key存在,則更新value的值. 若key不存在,則先建立屬性key再對其賦值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

三個方法一塊兒用:

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


# 判斷Myclass是否有gender屬性,有則打印,沒有則添加
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