mixin helper class for unknown attribute access?

[Steven D'Aprano]

On Mon, 31 Oct 2005 05:12:11 -0800, Sam Pointon wrote:

> One alrady exists, __slots__.
> 
>>>> class Foo(object):
> 	__slots__ = ['bar', 'baz', 'qig']
> 
> 
>>>> f = Foo()
>>>> f.foo = 'bar'
> 
> Traceback (most recent call last):
>   File "<pyshell#5>", line 1, in -toplevel-
>     f.foo = 'bar'
> AttributeError: 'Foo' object has no attribute 'foo'
>>>> f.bar = 'foo'


__slots__ are NOT intended to be used to limit Python's dynamic nature.
Whether you call this usage a misuse or a serendipitous side-effect is a
matter of opinion.


> However, __slots__ only works for class instances, so if you're messing
> around with uninitialised classes (not a good idea outside the
> singleton pattern or very functional-style code) it won't work.


__slots__ only work with new-style classes, not classic classes.

Before using __slots__, read this:

http://www.python.org/doc/current/ref/slots.html

Then read this recipe:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/252158


-- 
Steven.