From 3700cc3ad66de1c7b98e1d1e73eeddaa24da1fa0 Mon Sep 17 00:00:00 2001 From: Ethan Furman Date: Wed, 14 Jan 2015 22:02:10 -0800 Subject: [PATCH] Issue20467: clarify __init__'s role --- Doc/reference/datamodel.rst | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 5a6c763769..44901af718 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -1225,13 +1225,17 @@ Basic customization .. index:: pair: class; constructor - Called when the instance is created. The arguments are those passed to the + Called after the instance has been created (by :meth:`__new__`), but before + it is returned to the caller. The arguments are those passed to the class constructor expression. If a base class has an :meth:`__init__` method, the derived class's :meth:`__init__` method, if any, must explicitly call it to ensure proper initialization of the base class part of the instance; for - example: ``BaseClass.__init__(self, [args...])``. As a special constraint on - constructors, no value may be returned; doing so will cause a :exc:`TypeError` - to be raised at runtime. + example: ``BaseClass.__init__(self, [args...])``. + + Because :meth:`__new__` and :meth:`__init__` work together in constructing + objects (:meth:`__new__` to create it, and :meth:`__init__` to customise it), + no non-``None`` value may be returned by :meth:`__init__`; doing so will + cause a :exc:`TypeError` to be raised at runtime. .. method:: object.__del__(self) -- 2.50.1