[Python-ideas] Attribute Docstrings and Annotations

[Tony Lownds]

On May 31, 2007, at 6:15 AM, Ali Sabil wrote:

> Hello all,
>
> I was looking into function annotations, that are to be introduced  
> in Python3k, and I found this old message sent to this mailing  
> list : http://mail.python.org/pipermail/python-ideas/2007-January/ 
> 000037.html
>
> I would like to restart the discussion of attribute annotation,  
> because in my opinion it can be a very powerful feature. I  
> personally think about using it for SOAP message serialization, or  
> any kind of XML serialization, the Idea would be to annotate  
> various object attribues to be either marshaled as XML Elements or  
> XML Attributes of the current Node that reflects the Object.
>

Hi Ali,

I'm afraid the PEP deadline has passed, restarting the discussion would
not change that.

Your use case sounds interesting. I know there are a lot of other use  
cases for
attribute meta-data. However there are lots of ways to achieve  
attribute meta data
storage.

# Via naming convention
class A:
   attr = 1
   f_attr = int

# Via decorators
class A:
   attr = annotated_value(1, int)

# Via a separate class
class A:
   class meta:
     attr = int
   attr = 1

# Compare to attribute annotation syntax
class A:
   attr: int = 1

Each of the existing idioms I have seen or used has issues, mostly  
minor. I suspect that because
the existing ways don't have glaring deficiencies, even if it were  
before the PEP deadline, a renewed
push on the proposal would have encountered a lot more resistance.

I still think the syntax is elegant in symmetry and provides a  
unified and improved idiom for
a common use case.

-Tony

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