[Python-Dev] PEP 520: Ordered Class Definition Namespace
ncoghlan at gmail.com
Thu Jun 9 17:39:40 EDT 2016
On 7 June 2016 at 20:17, Eric Snow <ericsnowcurrently at gmail.com> wrote:
> On Tue, Jun 7, 2016 at 6:20 PM, Ethan Furman <ethan at stoneleaf.us> wrote:
>> If __definition_order__ is supposed to be immutable as well as read-only
>> then we should convert non-tuples to tuples. No point in letting that
>> user bug slip through.
> Do you mean if a class explicitly defines __definition_order__? If
> so, I'm not clear on how that would work. It could be set to
> anything, including None or a value that does not iterate into a
> definition order. If someone explicitly set __definition_order__ then
> I think it should be used as-is.
I'm guessing Ethan is suggesting defining it as:
__definition_order__ = tuple(ns["__definition_order__"])
When the attribute is present in the method body.
That restriction would be comparable to what we do with __slots__ today:
>>> class C:
... __slots__ = 1
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable
Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
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