[issue11610] Improving property to accept abstract methods

[Darren Dale]

Darren Dale <dsdale24 at gmail.com> added the comment:

On Sat, May 14, 2011 at 5:17 PM, Benjamin Peterson
<report at bugs.python.org> wrote:
>
> Benjamin Peterson <benjamin at python.org> added the comment:
>
> 2011/5/14 Darren Dale <report at bugs.python.org>:
>>
>> Darren Dale <dsdale24 at gmail.com> added the comment:
>>
>> On Sat, May 14, 2011 at 4:28 PM, Benjamin Peterson
>> <report at bugs.python.org> wrote:
>>>
>>> Benjamin Peterson <benjamin at python.org> added the comment:
>>>
>>> I still dislike the reduntancy of having abstractmethod and abstractproperty on a method. I think a better idea is having abstractproperty.abstract(getter/setter/deleter).
>>
>> Right, but I explained why the redundancy is necessary in order to
>> preserve backwards compatibility. If the abstractproperty constructor
>> were changed to tag methods it receives as abstract, it would be a
>> backwards-incompatible change in behavior with potential consequences
>> for consumers of abstractproperty.
>
> I'm not suggesting that it tag methods it receives as abstract.
> @getter/setter/deleter would still act the same.

I wasn't talking about @getter/setter/deleter. I tried to be clear
that I was talking about the abstractproperty() constructor. It
doesn't currently tag the methods it receives as abstract, and to
change this would be a backward incompatible change. Therefore,
@abstractmethod should be used to tag methods as abstract before
passing them to the abstractproperty() constructor, and the abc
documentation should be changed to reflect this.

>> abstractproperty.abstract(getter/setter/deleter) could be implemented,
>> but it still wouldn't change the fact that if a getter/setter is
>> intended to be abstract, it needs to be decorated with @abstractmethod
>> before being passed to the abstractproperty() constructor.
>
> Why not? You could set the __abstractmethod__ attribute in abstractgetter().

I was not talking about decorating before passing @abstractgetter. I
was talking about decorating before passing to the abstractproperty()
constructor.

>> This is
>> true today in <=python-3.2: its not mentioned in the documentation,
>> but the behavior exists all the same.
>
>>
>> Properties are composite objects, their behavior is defined by it is
>> the setters/getters/deleters they receive. So its actually a very
>> conceptually clean solution to decorate a method with @abstractmethod,
>> and it fits really nicely with the rest of the abc module. Why does
>> abstractproperty need special abstract(setter/getter/deleter) methods,
>> when the existing methods combine with @abstractmethod in a clean way
>> to produce the exact same result? To save one line of code?
>
> I find it produces a rather unfortunate ordering dependency for the
> decorators which is hard to remember.

Why is it difficult to remember that you need to tag a method as
abstract before passing it to the property?

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue11610>
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