why extending copy.*

Chris Liechti cliechti at gmx.net
Fri Jun 21 17:01:55 EDT 2002

Uwe Mayer <merkosh at hadiko.de> wrote in 
news:MPG.177d438123ae240598968d at news.rz.uni-karlsruhe.de:

> hi,
> i need shallow and deep copies of objects and I found the copy module in 
> the reference library which does quite a good job.
> however, they write that one could implement the copy protocol by 
> extending/ overwriting the __copy__() and __deepcopy__() method.
> since __copy__() and __deepcopy__() already duplicate the instance 
> dictionary, __deepcopy__() even recursively. For what reasons would I 
> want to extend /overwrite the capabilities of __copy__() or __deepcopy__
> ()?

its important when you use external resources. e.g. a file descriptor can 
be duplicated so that you can call close() on each file object (in a copied 
object and in the original) without infuence on the other (i think, but 
you'll get the point...)

or a connection to a DB could be opened on the copied object so that the 
copy and the original do not interfere.


Chris <cliechti at gmx.net>

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