[Python-Dev] Re: PEP 322: Reverse Iteration
Phillip J. Eby
pje at telecommunity.com
Wed Nov 5 09:54:43 EST 2003
At 07:29 AM 11/5/03 -0500, Raymond Hettinger wrote:
>Not really. When you go to write the code, it becomes clear that it
>doesn't apply to enumerate or the other itertools. The issue is that
>the iterator object holds only the result of iter(iterable) and is in no
>position to re-probe the underlying iterable to see if it supports
>reverse iteration. The iterator object has no way of knowing in advance
>that it is going to be called by reversed().
Why not change enumerate() to return an iterable, rather than an
iterator? Then its __reversed__ method could attempt to delegate to the
underlying iterable. Is it likely that anyone relies on enumerate() being
an iterator, rather than an iterable?
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