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Diffstat (limited to 'Doc/whatsnew/3.6.rst')
| -rw-r--r-- | Doc/whatsnew/3.6.rst | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/Doc/whatsnew/3.6.rst b/Doc/whatsnew/3.6.rst index e560fba..031bf79 100644 --- a/Doc/whatsnew/3.6.rst +++ b/Doc/whatsnew/3.6.rst @@ -92,6 +92,7 @@ Windows improvements: :pep:`4XX` - Python Virtual Environments PEP written by Carl Meyer +.. XXX PEP 520: :ref:`Preserving Class Attribute Definition Order<whatsnew-deforder>` New Features ============ @@ -271,6 +272,31 @@ Example of fatal error on buffer overflow using (Contributed by Victor Stinner in :issue:`26516` and :issue:`26564`.) +.. _whatsnew-deforder: + +PEP 520: Preserving Class Attribute Definition Order +---------------------------------------------------- + +Attributes in a class definition body have a natural ordering: the same +order in which the names appear in the source. This order is now +preserved in the new class's ``__definition_order__`` attribute. It is +a tuple of the attribute names, in the order in which they appear in +the class definition body. + +For types that don't have a definition (e.g. builtins), or the attribute +order could not be determined, ``__definition_order__`` is ``None``. + +Also, the effective default class *execution* namespace (returned from +``type.__prepare__()``) is now an insertion-order-preserving mapping. +For CPython, it is now ``collections.OrderedDict``. Note that the +class namespace, ``cls.__dict__``, is unchanged. + +.. seealso:: + + :pep:`520` - Preserving Class Attribute Definition Order + PEP written and implemented by Eric Snow. + + Other Language Changes ====================== |