[Python-3000] PEP 3119 - Introducing Abstract Base Classes (original) (raw)

Tony Lownds tony at PageDNA.com
Fri Apr 27 20:17:41 CEST 2007

On Apr 27, 2007, at 10:40 AM, Bill Janssen wrote:

Jim Jewett wrote:

On 4/27/07, Barry Warsaw <barry at python.org> wrote:

- - Attributes. Interfaces allow you to make assertions about attributes, not just methods, while ABCs necessarily cover only methods. Why can't they have data attributes as well? I agree with Jim. It seems to me that documenting standard attributes of a type is one thing that ABC's should be able to do. Perhaps a "@abstractattribute" decorator of some sort? Perhaps a class decorator "@attributes(name1, name2, ...)"? Attributes with those names would be automatically added to an instance, initialized to None, before the first init method would be called.

+0 on abstract attributes. Methods seem to dominate most APIs that make use of interfaces, but there are always a few exceptions.

Attribute annotations could provide an elegant solution here.

class ABC: concrete_attribute : "any expression" = None abstract_attribute : "any expression"

I posted about attribute annotations before on python-ideas and there
was lukewarm response. If anyone thinks a PEP on attribute annotations is
worth submitting, let me know.

Thanks -Tony

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