Fred Drake wrote:
On May 21, 2008, at 5:41 AM, Nick Coghlan wrote:
While a proxy class written in C would no doubt be faster than one
written in Python, one of the things I'm hoping to achieve is for the
stdlib generic proxy to serve as an example for people writing their
own new-style proxy classes in addition to being usable as a base
class (Adam Olsen suggested ProxyMixin instead of ProxyBase as a
possible name).
The idea that it would serve as an example seems odd; the reason to make
things part of the standard library is because their implementation
needs to track the Python core closely. For a proxy, it would be the
need to reflect additional slot methods as they're added.
It does that too - the unit tests I just added to the tracker issue for
this proposal will actually start to fail if something is added to the
operator module without the unit tests for the proposed ProxyMixin being
updated appropriately (it would actually probably be a good thing to
have something similar in the weakref.proxy test suite to prevent a
repeat of our effort with forgetting to update that when the
operator.index slot was added)
A Python
implementation may be able to do this just fine, but the performance
penalty would make it uninteresting for many large applications.
It should still be faster than the classic class __getattr__ based proxy
implementations it is primarily intended to replace. People that are
already using a C-based implementation like zope.proxy aren't going to
be affected by the removal of classic classes in 3.0, since they weren't
relying on them anyway.
In many ways, the TestProxyMixin test suite may prove more useful in the
long run than the ProxyMixin class itself, since the test suite provides
a template for how to test that a proxy class is doing its job, and also
to automatically detect when new C-level operations have been added to
the interpreter that the proxy class doesn't support.
For what it's worth, zope.proxy does support subclassing.
But not in a mixin style - since zope.proxy is an extension class in its
own right, it can't be combined with other extension classes.
The Python version can be combined with anything.
Cheers,
Nick.
--
Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia
---------------------------------------------------------------
http://www.boredomandlaziness.org
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