[Python-Dev] PEP 231, __findattr__()

[Christian Tismer]

Hi Barry,

"Barry A. Warsaw" wrote:
> 
> I've just uploaded PEP 231, which describes a new hook in the instance
> access mechanism, called __findattr__() after a similar mechanism that
> exists in Jython (but is not exposed at the Python layer).
> 
> You can do all kinds of interesting things with __findattr__(),
> including implement the __of__() protocol of ExtensionClass, and thus
> implicit and explicit acquisitions, in pure Python.  You can also do
> Java Bean-like interfaces and C++-like access control.  The PEP
> contains sample implementations of all of these, although the latter
> isn't as clean as I'd like, due to other restrictions in Python.
> 
> My hope is that __findattr__() would eliminate most, if not all, the
> need for ExtensionClass, at least within the Zope and ZODB contexts.
> I haven't tried to implement Persistent using it though.

I have been using ExtensionClass for quite a long time, and
I have to say that you indeed eliminate most of its need
through this super-elegant idea. Congratulations!

Besides acquisition and persitency interception,
wrapping plain C objects and giving them Class-like behavior
while retaining fast access to internal properties but being
able to override methods by Python methods was my other use
of ExtensionClass. I assume this is the other "20%" part you
mention, which is much harder to achieve?
But that part also looks easier to implement now, by the support
of the __findattr__ method.

> Since it's a long PEP, I won't include it here.  You can read about it
> at this URL
> 
>     http://python.sourceforge.net/peps/pep-0231.html

Great. I had to read it twice, but it was fun.

ciao - chris

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