From 119479f70550cf4323ba1eb8cdda88a47681362b Mon Sep 17 00:00:00 2001 From: Ethan Furman Date: Wed, 14 Jan 2015 21:56:10 -0800 Subject: [PATCH] Issue20467: clarify __init__'s role --- Doc/reference/datamodel.rst | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 160af305d87..e5e53c118e8 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -1081,13 +1081,17 @@ Basic customization .. index:: pair: class; constructor - Called when the instance is created. 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. + 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...])``. + + 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)