python的getattr用于normal attribute lookup fails的情况, 例如某attribute不存在 而getattribute会拦截所有的atttribute lookup 操作，不论这个attribute 存在与否
看代码，当我们search for并不存在p.f的时候，会调用__getattr__
class P:
x = 'a'
def __init__(self,n=0):
self.n = n
def __getattr__(self,name):
return("__geattr__ will be called when normal attribute get failed")
'''
def __getattribute__(self, name):
return("__getattribute__ will be called always")
'''
def test_():
p = P()
print(p.x)
print(p.n)
print(p.__dict__)
#with parameter, equals p.__dict__
print(vars(p))
#searching for a attribute which is not exist
print(p.f)
print(getattr(p, 'n'))
print(getattr(p, 'x'))
运行结果是
a
0
{'n': 0}
{'n': 0}
__geattr__ will be called when normal attribute get failed
0
a
下面的这个例子，因为有__getattribute__的存在，所有的attribute looup操作都会通过该函数
class B:
x = 'ba'
def __init__(self,n=100):
self.n = n
def __getattr__(self,name):
return("__geattr__ will be called when normal attribute get failed")
def __getattribute__(self, name):
return("__getattribute__ will be called always")
def test2_():
b = B()
print(b.x)
print(b.n)
print(b.__dict__)
#With parameter, equals to b.__dict__
print(vars(b))
#searching for a attribute which is not exist
print(b.f)
print(getattr(b, 'n'))
print(getattr(b, 'x'))
运行结果是
__getattribute__ will be called always
__getattribute__ will be called always
__getattribute__ will be called always
__getattribute__ will be called always
__getattribute__ will be called always
__getattribute__ will be called always
__getattribute__ will be called always
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