From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Date: Sun, 20 Feb 2022 05:25:57 +0000 (-0800) Subject: Improve discussion about how __getattr__ is invoked. (GH-31435) (GH-31437) X-Git-Tag: v3.10.3~76 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ea3e0421b04a6081d604786a40e7f27ff854b428;p=thirdparty%2FPython%2Fcpython.git Improve discussion about how __getattr__ is invoked. (GH-31435) (GH-31437) --- diff --git a/Doc/howto/descriptor.rst b/Doc/howto/descriptor.rst index f8b1e00d96fa..f2e2f7ee68c2 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 -----------------------