New submission from Nick Coghlan: Creating this as a separate issue so as not to delay incorporation of the accepted PEP.
One legitimate criticism of the accepted PEP 435 is that the combination of requiring explicit assignment of values *and* allowing aliasing by default is that aliases may be created inadvertently. I believe we can actually do better than the initial implementation by making the following work: >>> class Shape(Enum): ... square = 2 ... diamond = 1 ... circle = 3 ... alias_for_square = square ... >>> Shape.square <Shape.square: 2> >>> Shape.alias_for_square <Shape.square: 2> >>> Shape(2) <Shape.square: 2> While *disallowing* the following: >>> class Shape(Enum): ... square = 2 ... diamond = 1 ... circle = 3 ... alias_for_square = 2 ... How, do you ask? By wrapping non-descriptors on assignment in a placeholder type, and keeping track of which values we have already seen. If a new attribute is mapped to a placeholder, then that's fine, we accept it as an explicit declaration of an alias. However, if it's mapped directly to a repeat value, then that would be disallowed (as it was in earlier versions of the PEP). ---------- messages: 188981 nosy: ncoghlan priority: normal severity: normal stage: needs patch status: open title: Alternate approach to aliasing for PEP 435 type: enhancement versions: Python 3.4 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue17959> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
