gh-112331: Fix reference manual description of attribute lookup mechanics

[rhettinger]

Make the lookup mechanics description match the logic found in slot_tp_getattr_hook in `Objects/typeobject.c'.

Notably, mention of __getattribute__ was missing.

• Issue: Reference Manual 6.3.1: wrong method mentioned #112331

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📚 Documentation preview 📚: https://cpython-previews--112375.org.readthedocs.build/

[AlexWaygood]

Looks like a clear improvement to me. Left one minor suggestion, and a question:

[AlexWaygood]

Suggested change

	:meth:`~object.__getattribute__` method or the :meth:`~object.__getattr__`
	:meth:`~object.__getattribute__` method and/or the :meth:`~object.__getattr__`

[rhettinger]

I think "or" is fine. The "and/or" is correct but looks weird and doesn't read well.

[AlexWaygood]

I disagree that it looks weird, but won't insist

[AlexWaygood]

Of course, it is possible to create badly behaved objects that raise other exceptions from __getattribute__:

>>> class Foo:
...     def __getattribute__(self, attr):
...         if attr == 'foo':
...             raise TypeError('no')
...         return object.__getattribute__(self, attr)
...
>>> f = Foo()
>>> f.a = 1
>>> f.a
1
>>> f.b
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    f.b
  File "<stdin>", line 5, in __getattribute__
    return object.__getattribute__(self, attr)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Foo' object has no attribute 'b'
>>> f.foo
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    f.foo
  File "<stdin>", line 4, in __getattribute__
    raise TypeError('no')
TypeError: no

Does that need to be mentioned here? Or is it too obscure?

[rhettinger]

No need. Any code can raise a weird error at any time but we don't need to mention that in the docs in the thousands of places where this could occur:

This wording corresponds to what the code actually does:

def getattr_hook(obj, name):
    "Emulate slot_tp_getattr_hook() in Objects/typeobject.c"
    try:
        return obj.__getattribute__(name)
    except AttributeError:
        if not hasattr(type(obj), '__getattr__'):
            raise
    return type(obj).__getattr__(obj, name)

[AlexWaygood]

I disagree that it looks weird, but won't insist

[miss-islington-app]

Thanks @rhettinger for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11, 3.12.
🐍🍒⛏🤖

[bedevere-app]

GH-112412 is a backport of this pull request to the 3.12 branch.

[bedevere-app]

GH-112413 is a backport of this pull request to the 3.11 branch.