Understanding the difference between __getattr__ and __getattribute__

Question

I am trying to understand the difference between __getattr__ and __getattribute__, however, I am failing at it.

The answer to the Stack Ove

Answer 1

I have gone through other's excellent explanation. However, I found a simple answer from this blog Python Magic Methods and __getattr__. All the following are from there.

Using the __getattr__ magic method, we can intercept that inexistent attribute lookup and do something so it doesn’t fail:

class Dummy(object):

    def __getattr__(self, attr):
        return attr.upper()

d = Dummy()
d.does_not_exist # 'DOES_NOT_EXIST'
d.what_about_this_one  # 'WHAT_ABOUT_THIS_ONE'

But if the attribute does exist, __getattr__ won’t be invoked:

class Dummy(object):

    def __getattr__(self, attr):
        return attr.upper()

d = Dummy()
d.value = "Python"
print(d.value)  # "Python"

__getattribute__ is similar to __getattr__, with the important difference that __getattribute__ will intercept EVERY attribute lookup, doesn’t matter if the attribute exists or not.

class Dummy(object):

    def __getattribute__(self, attr):
        return 'YOU SEE ME?'

d = Dummy()
d.value = "Python"
print(d.value)  # "YOU SEE ME?"

In that example, the d object already has an attribute value. But when we try to access it, we don’t get the original expected value (“Python”); we’re just getting whatever __getattribute__ returned. It means that we’ve virtually lost the value attribute; it has become “unreachable”.