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author | Ethan Furman <ethan@stoneleaf.us> | 2014-09-17 02:13:31 (GMT) |
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committer | Ethan Furman <ethan@stoneleaf.us> | 2014-09-17 02:13:31 (GMT) |
commit | f75805edb8d1399586bae6c12611705a4345b572 (patch) | |
tree | a2e497eb33ff33021c9601534a00f42b5bf2e2e0 | |
parent | 0081f23a08b6f661a57a62c9ab8ce38bf90e8ed7 (diff) | |
download | cpython-f75805edb8d1399586bae6c12611705a4345b572.zip cpython-f75805edb8d1399586bae6c12611705a4345b572.tar.gz cpython-f75805edb8d1399586bae6c12611705a4345b572.tar.bz2 |
Issue21738: clarify usage of __new__ in Enum subclasses
-rw-r--r-- | Doc/library/enum.rst | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/Doc/library/enum.rst b/Doc/library/enum.rst index acdcf7f..503d305 100644 --- a/Doc/library/enum.rst +++ b/Doc/library/enum.rst @@ -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. |