initializing mutable class attributes

[Alex Martelli]

Dan Perl <dperl at rogers.com> wrote:

> I found a small hole in the initial code suggestion and I fixed it.  Try and
> find the difference:
>     class test(object):
>         def __new__(typ, *args, **kwargs):
>             obj = object.__new__(typ)
>             obj.attr1 = 666
>             typ.__init__(obj, *args, **kwargs)
>             return obj
> 
>     class derived(test):
>         def __init__(self, arg1, arg2):
>             self.attr2 = arg1
>             self.attr3 = arg2
> 
>     d = derived(111, 222)
>     print d.attr1, d.attr2
>     print isinstance(d, test)
> 
> So, what do people think about it?  Alex, would this be good for a recipe in
> the Python Cookbook?

I might run it side by side with my custom metaclass, sure.  I'm not
sure why you're running typ.__init__ from within test.__new__ -- it
seems to me that will result in double-running cases.


Alex