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 think the other answers have done a great job of explaining the difference between __getattr__ and __getattribute__, but one thing that might not be clear is why you would want to use __getattribute__. The cool thing about __getattribute__ is that it essentially allows you to overload the dot when accessing a class. This allows you to customize how attributes are accessed at a low level. For instance, suppose I want to define a class where all methods that only take a self argument are treated as properties:

# prop.py
import inspect

class PropClass(object):
    def __getattribute__(self, attr):
        val = super(PropClass, self).__getattribute__(attr)
        if callable(val):
            argcount = len(inspect.getargspec(val).args)
            # Account for self
            if argcount == 1:
                return val()
            else:
                return val
        else:
            return val

And from the interactive interpreter:

>>> import prop
>>> class A(prop.PropClass):
...     def f(self):
...             return 1
... 
>>> a = A()
>>> a.f
1

Of course this is a silly example and you probably wouldn't ever want to do this, but it shows you the power you can get from overriding __getattribute__.