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author | Raymond Hettinger <rhettinger@users.noreply.github.com> | 2022-02-20 05:02:30 (GMT) |
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committer | GitHub <noreply@github.com> | 2022-02-20 05:02:30 (GMT) |
commit | 12a2e41e8a276ec3a68f3e5f94b02752185c66fb (patch) | |
tree | 05714c6dd8fcd7bd1d52c6dc076d9919bb1b398d | |
parent | 0a8a8e7454c6565cf1554d5f23314e4c70960bcd (diff) | |
download | cpython-12a2e41e8a276ec3a68f3e5f94b02752185c66fb.zip cpython-12a2e41e8a276ec3a68f3e5f94b02752185c66fb.tar.gz cpython-12a2e41e8a276ec3a68f3e5f94b02752185c66fb.tar.bz2 |
Improve discussion about how __getattr__ is invoked. (GH-31435)
-rw-r--r-- | Doc/howto/descriptor.rst | 16 |
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 ----------------------- |