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[Python-Dev] Re: Reiterability

Alex Martelli aleaxit at yahoo.com
Mon Oct 20 18:09:39 EDT 2003 
On Monday 20 October 2003 07:43 pm, Guido van Rossum wrote:
   ...
> I'm not sure why you say it's separate from cloning; it seems to me
> that copy.copy(iter(range(10))) should return *exactly* what we'd want
> the proposed clone operation to return.

I'd be tickled pink if it did, but I would have expected a shallow copy to
return an iterator that's not necessarily independent from the starting one.
Maybe I have a bad mental model of the "depth" (indirectness) of
iterators?

> I see this as a plea to add __copy__ and __deepcopy__ methods to all
> standard iterators for which it makes sense.  (Or maybe only __copy__
> -- I'm not sure what value __deepcopy__ would add.)

Hmmm, copy the underlying sequence as well?  Don't have any use
case for it, but that's what would feel unsurprising to me (as I have
already mentioned I may not have the right mental model of an
iterator...).

> I find this a reasonable request for the iterators belonging to
> stndard containers (list, tuple, dict).  I guess that some of the
> iterators in itertools might also support this easily.  Perhaps this
> would be the road to supporting iterator cloning?

It would surely do a lot to let me clone things, yes, and in fact
doing it with the existing __copy__ protocol sounds much better
than sprouting a new one.


(Thanks for the confirmations and clarifications on file internals.
btw, any news of the new experimental file things you were
playing with back at PythonUK...?)


Alex
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