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Issue21738: clarify usage of __new__ in Enum subclasses

This commit is contained in:
Ethan Furman 2014-09-16 19:14:00 -07:00
parent 6a8e0fbcfb f75805edb8
commit 52351c7037
1 changed files with 9 additions and 6 deletions
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15
Doc/library/enum.rst
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@ -586,8 +586,7 @@ Avoids having to specify the value for each enumeration member::
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 @@ but not of the class::
>>> 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.