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authorRaymond Hettinger <rhettinger@users.noreply.github.com>2022-02-20 05:02:30 (GMT)
committerGitHub <noreply@github.com>2022-02-20 05:02:30 (GMT)
commit12a2e41e8a276ec3a68f3e5f94b02752185c66fb (patch)
tree05714c6dd8fcd7bd1d52c6dc076d9919bb1b398d
parent0a8a8e7454c6565cf1554d5f23314e4c70960bcd (diff)
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Improve discussion about how __getattr__ is invoked. (GH-31435)
-rw-r--r--Doc/howto/descriptor.rst16
1 files changed, 7 insertions, 9 deletions
diff --git a/Doc/howto/descriptor.rst b/Doc/howto/descriptor.rst
index 4f6389e..825e9d0 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
-----------------------