On Sun, Jun 19, 2022 at 01:34:35AM +0100, Rob Cliffe via Python-ideas 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 How does a generic iterator, including generators, know whether or not item 42 has already been seen? islice for generators is really just a thin wrapper around an iterator that operates something vaguely like this: for i in range(start): next(iterator) # throw the result away for i in range(start, end): yield next(iterator) It doesn't need to keep track of the last index seen, it just blindly advances through the iterator, with some short-cuts for the sake of efficiency. -- Steve _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/A74YRQJ4QID72GE5I2A3QKOU6NHLJNCD/ Code of Conduct: http://python.org/psf/codeofconduct/