pass object or use self.object?

Lie Ryan lie.1296 at
Thu Apr 8 21:05:15 EDT 2010

On 04/08/10 18:20, Bruno Desthuilliers wrote:
> Lie Ryan a écrit :
>> On 04/07/10 18:34, Bruno Desthuilliers wrote:
>>> Lie Ryan a écrit :
>>> (snip)
>>>> Since in function in python is a first-class object, you can instead do
>>>> something like:
>>>> def process(document):
>>>>     # note: document should encapsulate its own logic
>>>>     document.do_one_thing()
>>> Obvious case of encapsulation abuse here. Should a file object
>>> encapsulate all the csv parsing logic ? (and the html parsing, xml
>>> parsing, image manipulation etc...) ? Should a "model" object
>>> encapsulate the presentation logic ? I could go on for hours here...
>> Yes, but no; you're taking it out of context. Is {csv|html|xml|image}
>> parsing logic a document's logic? Is presentation a document's logic? If
>> they're not, then they do not belong in document.
> Is len() a list logic ? If yes, it should belong to list !-)

Yes, that's why list.__len__() belongs to list while len() is a
convenience function that doesn't carry any concrete implementation.

> There are two points here : the first is that we (that is, at least, you
> and me) just don't know enough about the OP's project to tell whether
> something should belong to the document or not. period. 

I think I see your point here. I retract my suggestion that it is
suitable for OP's purpose since I just realized OP is in a better
position to make the decision.

> The second point
> is that objects don't live in a splendid isolation, and it's perfectly
> ok to have code outside an object's method working on the object.
> wrt/ these two points, your "document should encapsulate its own logic"
> note seems a bit dogmatic (and not necessarily right) to me - hence my
> answer.

I agree with you about there are certain logics that should not be
inside the object (that's why I qualify the statement with `should`).
Glue logic, by definition, cannot be inside an object. I don't think we
are actually in disagreement here. But I think the dogma, followed with
caution, is generally good.

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