Python

传送门

1. https://docs.python.org/3/reference/datamodel.html#object.__getattr__
2. https://docs.python.org/3/reference/datamodel.html#object.__getattribute__
3. https://stackoverflow.com/questions/4295678/understanding-the-difference-between-getattr-and-getattribute
4. https://stackoverflow.com/questions/3278077/difference-between-getattr-vs-getattribute

区别

1. 当正常访问属性失败，即f.x，x不存在，会触发__getattr__
2. 无论有无f.x，都会触发__getattibute__

Talk is cheap

__getattr__单个出现

class Foo:
    
    def __init__(self, x):
        self.x = x

    def __getattr__(self, item):
        #return self.__dict__[item]
        return '__getattr__'

f1 = Foo(1)
print(f1.x)
print(f1.xxxxxx)    #访问不存在的属性访问，触发__getattr__

__getattribute__单个出现

class Foo:

    def __init__(self, x):
        self.x = x

    def __getattribute__(self, item):
        return '__getattribute__'


f1 = Foo(1)
print(f1.x)     # 访问存在的属性，也会直接执行__getattribute__
print(f1.xxx)   # 访问不存在的属性，也会直接执行__getattribute__

__getattr__和__getattibute__同时存在

class Foo:

    def __init__(self, x):
        self.x = x

    def __getattr__(self, item):
        return '执行的是我，__getattr__'
        # return self.__dict__[item]

    def __getattribute__(self, item):
        print('不管属性是否存在，我都执行，__getattribute__')
        raise AttributeError('__getattribute__的AttributeError')
        

f1 = Foo(1)
#  当两者同时存在的时候，只会执行__getattribute__；如果在__getattribute__过程中抛出AttributeError，那么就执行__geattr__
print(f1.x)     
# print(f1.xx)

18+ Warning

最好不要使用__getattribute__，不然有可能导致无限递归的可能。