Order in metaclass

Carlos Ribeiro carribeiro at gmail.com
Wed Oct 13 22:24:34 CEST 2004


On Wed, 13 Oct 2004 21:32:20 +0200, Thomas Heller <theller at python.net> wrote:
> And for your original question: why do you insist on your new syntax,
> why don't you simply (as ctypes also does it) define the attributes in a
> list, when they have to have a certain order?

I can't speak for Nicolas, but I can for myself. There are three
reasons, in my particular case:

-- The order is already there, explicit in the way the code is
written. I see no reason to be forced to state it _again_, specially
considering the fact that this is prone to errors; for example,
missing elements, duplicated elements, or out-of-order elements (in
ordered differently in the code and in the list).

-- I make extensive use of nested structs. In this case it's _much_
easier to make mistakes as the ones mentioned above.

-- Using classes and inheritance, it's easy to add new members or
redefine existing ones. But I would need to re-state the full list for
any descendant. To make matters worse, in this case, whenever I make a
change to the base class, I would have to change _all_ descendant
classes. Not exactly good OO design. Of course, clever hacks could
possibly be used, but then, it wouldn't look any better than Nicolas
(or my own) ordered-attributes hack.


It's specially important to point out that I consider the source code
ordering to be _explicit_, and not implicit, as some people may
possibly say. In fact, is there anything more explicit than that? Only
people used to Python dicts would say otherwise.

-- 
Carlos Ribeiro
Consultoria em Projetos
blog: http://rascunhosrotos.blogspot.com
blog: http://pythonnotes.blogspot.com
mail: carribeiro at gmail.com
mail: carribeiro at yahoo.com



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