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Daniel Bickett said unto the world upon 2005-02-05 19:46:
> I was reading the "Pickling and inheritance are making me hurt"
> thread, and the latest suggestion (as of this posting) was to do with
> the __setstate__ and __getstate__ methods. They caught my attention
> because I hadn't encountered them before, and it reminded me that in
> the past I've never been able to very good, definitive documentation
> on newstyle classes. Googling for it gives little python tutorials on
> various sites, and even searching this newsgroup returns very specific
> questions, as a rule.
>
> Alas, the question: Does there exist a page that enumerates all of the
> features of the newstyle classes, and explains what they all do? If
> so, can anyone provide me with such a link?
>
> Thanks

Hi Daniel,

it doesn't yet answer the "definitive" part, but
<http://www.python.org/moin/NewClassVsClassicClass> is worth a look.

Best,

Brian vdB

Brian van den Broek wrote:
> Daniel Bickett said unto the world upon 2005-02-05 19:46:
>
>> I was reading the "Pickling and inheritance are making me hurt"
>> thread, and the latest suggestion (as of this posting) was to do with
>> the __setstate__ and __getstate__ methods. They caught my attention
>> because I hadn't encountered them before, and it reminded me that in
>> the past I've never been able to very good, definitive documentation
>> on newstyle classes. Googling for it gives little python tutorials on
>> various sites, and even searching this newsgroup returns very specific
>> questions, as a rule.
>>
>> Alas, the question: Does there exist a page that enumerates all of the
>> features of the newstyle classes, and explains what they all do? If
>> so, can anyone provide me with such a link?
>>
>> Thanks
>
>
> Hi Daniel,
>
> it doesn't yet answer the "definitive" part, but
> <http://www.python.org/moin/NewClassVsClassicClass> is worth a look.
>
> Best,
>
> Brian vdB

Yes, that's the best I've come across. But a clearer overall view, tied
in to the Language Reference, would be very helpful.

It would be good to have a clear exposition of the pros and cons of
__new__ usage.

Colin W.

> It would be good to have a clear exposition of the pros and cons of
> __new__ usage.

It is there mostly because __init__ would not work on immutable types.
OTOH, you probably do not want to use __new__ on mutable types
(once I was caught by this trap, google for "overriding list.__new__"
if you are interested).

Michele Simionato

Michele Simionato wrote:
>>It would be good to have a clear exposition of the pros and cons of
>>__new__ usage.
>
>
> It is there mostly because __init__ would not work on immutable types.
> OTOH, you probably do not want to use __new__ on mutable types
> (once I was caught by this trap, google for "overriding list.__new__"
> if you are interested).
>
> Michele Simionato
>
Thanks. The use of __new__ for immutable classes is described in:
http://www.python.org/2.2.3/descrintro.html

This distinction hadn't registered with me before.

The Martelli bible doesn't bring this out.

It seems to me that __new__ should probably be deprecated for mutable
classes.

Colin W.

Colin:
> It seems to me that __new__ should probably be deprecated for mutable
> classes.

Certainly not! It is useful for mutable classes too. One just must be
careful.

Michele Simionato