On 10/13/2017 02:35 AM, Martin Teichmann wrote:
Metaclasses currently tend to serve two distinct purposes:
1. Actually altering the runtime behaviour of a class and its children in
non-standard ways (e.g. enums, ABCs, ORMs)
2. Boilerplate reduction in class definitions, reducing the amount of code
you need to write as the author of that class
Nobody has a problem with using metaclasses for the first purpose - that's
what they're for.
I am that nobody. The examples you give would be much nicer solved
with decorators.
The same holds for enums. Inheriting from enums is possible, but
weird, given that you cannot add new enums to it. So, especially when
comparing to the dataclasses, the following looks appealing to me:
@enum
class Breakfast:
spam = 0
ham = 1
Things that will not work if Enum does not have a metaclass:
list(EnumClass) -> list of enum members
dir(EnumClass) -> custom list of "interesting" items
len(EnumClass) -> number of members
member in EnumClass -> True or False
- protection from adding, deleting, and changing members
- guards against reusing the same name twice
- possible to have properties and members with the same name (i.e. "value" and
"name")
--
~Ethan~
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
https://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
