On 20/06/2022 17:39, Jeremiah Paige wrote:
On Sat, Jun 18, 2022 at 5:42 PM Rob Cliffe via Python-ideas
<python-ideas@python.org> wrote:
To me, the natural implementation of slicing on a non-reusable
iterator
(such as a generator) would be that you are not allowed to go
backwards
or even stand still:
mygen[42]
mygen[42]
ValueError: Element 42 of iterator has already been used
I agree that indexing an iterator such that it could only go forward
feels like a reasonable and useful feature in python, but I disagree
about the ValueError. To me the above produces two values: the 43rd
and 85th elements produced by mygen. Anything else is a bizarre error
waiting to arise at obscure times. What if this iterator is passed to
another function? Used in a loop? Now this information about what
index has been used has to be carried around and checked on every access.
Oh, OK, I have no problem with that (except shouldn't it be the 43rd and
86th elements?). I guess which interpretation is more useful depends on
the use case.
Best wishes
Rob Cliffe
Regards,
Jeremiah
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