On Fri, Jul 22, 2016 at 8:48 AM, Chris Angelico <rosuav@gmail.com> wrote:
IMO, no. Some iterators can be restarted by going back to the original
iterable and requesting another iterator, but with no guarantee that
it will result in the exact same sequence (eg dict/set iterators).

Sequences don't give you this *guarantee* either.  A trivial example:

class MyList(list):
    def __getitem__(self, ndx):
        # In "real world" this might be meaningful condition and update
        if random() < .333:
            if isinstance(ndx, slice):
                for n in range(ndx.start, ndx.stop, ndx.step or 1):
                    self[n] += 1
            else:
                self[ndx] += 1
        return super().__getitem__(ndx)
 
What you might be looking at is a protocol for "bookmarking" or
"forking" an iterator. That might be more useful. For example:

How is this different from itertools.tee()?
 
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