[Python-Dev] Re: PEP 322: Reverse Iteration

Raymond Hettinger python at rcn.com
Wed Nov 5 22:25:19 EST 2003

> > * There is a small group (including Jeremy Fincher) that consider a
> > reversal protocol to be essential.
> And I think that as a protocol it needs a separate PEP, because new
> protocols are much more involved than new builtins.

Great idea.  The champions for __reverse__ can plead their case there.

> > * It is particularly useful for xrange() because it reduces the
> > to zero without touching the API.  The implementation patch on SF
> > that this can be done cleanly.  Essentially, __reverse__ forwards
> > call to __iter__ with the arguments rearranged for reverse order.
> The implementation could special-case xrange() and lists and "optimize
> the snot out of them" without the need for a general protocol.

Agreed!  I'll take __reversed__ out of the pep.

May I mark this one as accepted and move on?

Raymond Hettinger

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