How python attribute lookup process works?

Question

When i say \"python attribute lookup proccess\" i mean: what python does when you write x.foo??

Searching the web i didn\'t found to much docs about this, one of the

Answer 1

If you added print("Metaclass getattribute invoked:", self, name) you'd see:

>>> c.__getattribute__
Class getattribute invoked: <__main__.C object at 0x2acdbb1430d0> __getattribute__
Metaclass getattribute invoked: <class '__main__.C'> __name__
<bound method C.__getattribute__ of <__main__.C object at 0x2acdbb1430d0>>

The metaclass __getattribute__ is getting invoked in order to build the repr of the expression c.__getattribute__, so that it can print C's __name__.

btw, __getattribute__ works the same for classes and metaclasses; the attribute is looked up first on the instance then on the instance's type.

>>> Meta.foo = 1
>>> C.foo
('Metaclass getattribute invoked:', <class '__main__.C'>, 'foo')
1
>>> c.foo
('Class getattribute invoked:', <__main__.C object at 0x2acdbb1430d0>, 'foo')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 5, in __getattribute__
AttributeError: 'C' object has no attribute 'foo'
>>> C.bar = 2
>>> c.bar
('Class getattribute invoked:', <__main__.C object at 0x2acdbb1430d0>, 'bar')
2