[Python-checkins] Improve discussion about how __getattr__ is invoked. (GH-31435)

[rhettinger]

https://github.com/python/cpython/commit/12a2e41e8a276ec3a68f3e5f94b02752185c66fb
commit: 12a2e41e8a276ec3a68f3e5f94b02752185c66fb
branch: main
author: Raymond Hettinger <rhettinger at users.noreply.github.com>
committer: rhettinger <rhettinger at users.noreply.github.com>
date: 2022-02-19T23:02:30-06:00
summary:

Improve discussion about how __getattr__ is invoked. (GH-31435)

files:
M Doc/howto/descriptor.rst

diff --git a/Doc/howto/descriptor.rst b/Doc/howto/descriptor.rst
index 4f6389e3b2d48..825e9d0347f5d 100644
--- a/Doc/howto/descriptor.rst
+++ b/Doc/howto/descriptor.rst
@@ -696,10 +696,14 @@ a pure Python equivalent:
     >>> b.g == b['g'] == ('getattr_hook', b, 'g')
     True
 
+Note, there is no :meth:`__getattr__` hook in the :meth:`__getattribute__`
+code.  That is why calling :meth:`__getattribute__` directly or with
+``super().__getattribute__`` will bypass :meth:`__getattr__` entirely.
 
-Interestingly, attribute lookup doesn't call :meth:`object.__getattribute__`
-directly.  Instead, both the dot operator and the :func:`getattr` function
-perform attribute lookup by way of a helper function:
+Instead, it is the dot operator and the :func:`getattr` function that are
+responsible for invoking :meth:`__getattr__` whenever :meth:`__getattribute__`
+raises an :exc:`AttributeError`.  Their logic is encapsulated in a helper
+function:
 
 .. testcode::
 
@@ -744,12 +748,6 @@ perform attribute lookup by way of a helper function:
         ...
     AttributeError: 'ClassWithoutGetAttr' object has no attribute 'z'
 
-So if :meth:`__getattr__` exists, it is called whenever :meth:`__getattribute__`
-raises :exc:`AttributeError` (either directly or in one of the descriptor calls).
-
-Also, if a user calls :meth:`object.__getattribute__` directly, the
-:meth:`__getattr__` hook is bypassed entirely.
-
 
 Invocation from a class
 -----------------------