New PEP: Attribute Access Handlers

[Paul Prescod]

Bjorn Pettersen wrote:
> 
> Justification, Scenario 4:
> 
>    An existing class has a string attribute, however the most common
> operation on it is appending to the end. Through the profiler you find
> that this operation is taking up 95% of the applications time. You want
> to change the implementation to cStringIO for efficiency (total
> execution time for your application goes from 90 seconds to 3 secs).

Actually, I'm not sure if my proposal would help here. Appending to a
cStringIO is not an assignment operation...

> Perhaps you should add a few words about why you chose __attr_XXX__
> instead of __set/get/del_XXX__?  

That was actually the first proposal. But inheritance could get
confusing if you inherited set without get or get without set etc.

> Would both of them work for
> introspection for e.g. a GUI builder? I seem to remember that JavaBeans
> <shudder> looks for the presence of set/get methods to make attributes
> available, I'm not sure if Python could look at an objects __dict__ for
> that information under this proposal?

Interesting question...I think that's not a bad idea, actually. ON the
other hand, Python is so dynamic that there are other (more flexible)
ways that might not work in Java:

class foo:
    k=5
    j=7
    def a(): pass
   ....
    __readonly_properties__=[k,...]
    __readwrite_properties__=[j,...]
   ....

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 Paul Prescod - Not encumbered by corporate consensus
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