FW: [Python-Dev] PEP 322: Reverse Iteration
python at rcn.com
Tue Nov 4 19:49:06 EST 2003
> > I believe the assumption is that enumerate (as well as the proposed
> > would grow an __reversed__ method to handle just that usage.
Unfortunately, that idea didn't work out. The enumerate object does not
hold the original iterable; instead, it only has the result of
iter(iterable). Without having the iterable, I don't see a way for it
to call iterable.__reversed__. The essential problem that at creation
time, the enumerate object does know that it is going to be called by
No other sequence object has to have a __reversed__ method. Like its
cousin, __iter__, some objects may be a performance boost from a custom
iterator but none of them have to have it.
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