[Twisted-Python] Phasing out old-style classes

Glyph Lefkowitz glyph at twistedmatrix.com
Sun Oct 25 02:32:08 EDT 2009

On Oct 25, 2009, at 1:50 AM, James Y Knight wrote:

> On Oct 25, 2009, at 1:38 AM, Glyph Lefkowitz wrote:
>> What do you do?  Well, the obvious upgrade path here is to make a  
>> class which (A) inherits from "Library" to get Twisted  
>> functionality and (B) inherits from "object" to get new-style- 
>> ness.  So you go ahead and write:
>> # in your application
>> class Application(object, Library): pass
> Maybe the answer "why not" is obvious and I should already know it,  
> but wouldn't it be more obvious to write:
> class Application(Library, object): pass
> instead. That at least has the advantage of not blowing up if  
> Library later becomes newstyle, right?

Huh.  You may have just pointed out that I misunderstand the algorithm  
used to generate that error.  I thought that certain other hierarchies  
in cases more complex than the trivial one I presented would also give  
you that error if something became new-style in the middle, but I  
can't seem to generate any hierarchies that cause a problem.  Is it  
really this simple?  Always put 'object' at the *end* of your bases- 
list to declare the intention "I want to be new-style" and you'll be  
OK?  (If so, why is that?)

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