[Python-checkins] cpython (merge 3.4 -> default): Issue21738: clarify usage of __new__ in Enum subclasses

ethan.furman python-checkins at python.org
Wed Sep 17 04:14:35 CEST 2014


http://hg.python.org/cpython/rev/91ec34801232
changeset:   92447:91ec34801232
parent:      92445:cdd412347827
parent:      92446:28c21f09719e
user:        Ethan Furman <ethan at stoneleaf.us>
date:        Tue Sep 16 19:14:00 2014 -0700
summary:
  Issue21738: clarify usage of __new__ in Enum subclasses

files:
  Doc/library/enum.rst |  15 +++++++++------
  1 files changed, 9 insertions(+), 6 deletions(-)


diff --git a/Doc/library/enum.rst b/Doc/library/enum.rst
--- a/Doc/library/enum.rst
+++ b/Doc/library/enum.rst
@@ -586,8 +586,7 @@
 
     The :meth:`__new__` method, if defined, is used during creation of the Enum
     members; it is then replaced by Enum's :meth:`__new__` which is used after
-    class creation for lookup of existing members.  Due to the way Enums are
-    supposed to behave, there is no way to customize Enum's :meth:`__new__`.
+    class creation for lookup of existing members.
 
 
 OrderedEnum
@@ -743,7 +742,11 @@
     >>> dir(Planet.EARTH)
     ['__class__', '__doc__', '__module__', 'name', 'surface_gravity', 'value']
 
-A :meth:`__new__` method will only be used for the creation of the
-:class:`Enum` members -- after that it is replaced.  This means if you wish to
-change how :class:`Enum` members are looked up you either have to write a
-helper function or a :func:`classmethod`.
+The :meth:`__new__` method will only be used for the creation of the
+:class:`Enum` members -- after that it is replaced.  Any custom :meth:`__new__`
+method must create the object and set the :attr:`_value_` attribute
+appropriately.
+
+If you wish to change how :class:`Enum` members are looked up you should either
+write a helper function or a :func:`classmethod` for the :class:`Enum`
+subclass.

-- 
Repository URL: http://hg.python.org/cpython


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